FlightGear wiki - User contributions [en]

Flying the Shuttle - Space Shuttle Checklists

2024-11-23T11:31:41Z

Gingin: Links

{{DEFAULTSORT:Checklists}}
[[File:Spacetripready.png]][[File:Checklistready.png]]
{{Space Shuttle navigation}}

Here you will find all the materials/condensed checklist that you need for the differents phases of flight.

You can find the real one here, called Flight Data Files (FDF) [https://web.archive.org/web/20211020173004/https://www.nasa.gov/centers/johnson/news/flightdatafiles/index.html]

Here are my annotated FDF: 
 

'''Ascent Checklist''' [https://drive.google.com/open?id=1SUS7354nYi34BRrxQ4upMqqvTYAMI0Ot Ascent Checklist Annotated]
 
'''Post insertion Checklist''' [https://drive.google.com/open?id=0ByWr8dBBzTv3VWFldkpfSTZ6dFU Post Insertion Checklist Annotated] 
'''Deorbit Preparation Checklist''' [https://drive.google.com/open?id=0ByWr8dBBzTv3TlFjbkx5cHRESHM Deorbit Preparation Checklist Annotated] 
'''Entry Checklist''' [https://drive.google.com/open?id=0ByWr8dBBzTv3UEFTZTFoUGVWRTA Entry Checklist Annotated] 
'''TAL Checklist''' [https://drive.google.com/open?id=1O-W9DkF_FL-rMSKTkKiKbVhRU6hWIuKk TAL Checklist Annotated]

The Caution and Warning System fault messages annotated file contain all the fault messages implemented in the last dev version of December 2020.

'''Caution and Warning System Fault Messages''' [https://drive.google.com/file/d/1jGN9hUCghZFc1HAo67Ys9LurQoJKul8J/view?usp=drive_link CWS Fault Messages]

'''DPS Dictionnary System Management limit indicators''' [https://drive.google.com/file/d/1S-twHAqNxY3eKt7vRJCdzaBLKH1GFsfv/view?usp=drive_link DPS Dictionnary SM Indicators]

From 230 pages for ascent FDF, we go to less than 30 pages. A huge amount of datas of those FDF are for non-normal situations. It was important to have a quick look to know what to do in case of Engine failure for example.
Ascent checklist is pretty straight forward, reading from up to bottom with time of actions, where to look ( panels R2, L2, O 14 etc), and what to do.

Sometimes, a square root √ is preceding an item. It means " check that ( monitor)". For example, ''√ Evap out=60°'' means Check that the evap out of the Freon is around 60°

A special note for Post insertion and Deorbit Preparation Checklists. It's a bit different than previous one.
In this one, Commander, Pilot, Mission Specialist are supposed to do differents things in the cockpit, so the checks can be a bit weird to read at first glance.
Here some hints:

On the left, there is the timeline of the mission, in Mission Elapsed Time since lift off. Panel where to look is also shown ( R2, O12, etc)

Also, C P or MS is used to define who will do the actions ( Captain, Pilot, Specialist). Obviously here, it's gonna be us

[[File:WWDMhj.png|1000px|thumbnail|none]]

 
You see for example at Star Tracker activation, there is a rectangle with a number ( 12) and a page number 1-6
It's gonna be where you have to look to have the full procedure, we are at page 1-7 so we have to go back one page before to have the procedure for Star Tracker activation.
Same logic for almost all the others actions with a rectangle and page reference at the right of the line.

[[File:WWDMhj.png|1000px|thumbnail|none]]

All those checklists contain a lot of informations and actions that are not critical for flight safety.
The ones to perform absolutely are present in game via Help menu and Checklist.

Some very usefull Screens, sum up of all shortcuts to navigate in differents parts of the GPC GNC and SM functions

[[File:DPS1.png|1000px|thumbnail|none]]

[[File:DPS2.png|1000px|thumbnail|none]]

Flying the Shuttle - Space Shuttle Checklists

2024-11-23T11:18:59Z

Gingin: Links

{{DEFAULTSORT:Checklists}}
[[File:Spacetripready.png]][[File:Checklistready.png]]
{{Space Shuttle navigation}}

Here you will find all the materials/condensed checklist that you need for the differents phases of flight.

You can find the real one here, called Flight Data Files ( FDF) https://www.nasa.gov/centers/johnson/news/flightdatafiles/

Here are my annotated FDF: 
 

'''Ascent Checklist''' [https://drive.google.com/open?id=1SUS7354nYi34BRrxQ4upMqqvTYAMI0Ot Ascent Checklist Annotated]
 
'''Post insertion Checklist''' [https://drive.google.com/open?id=0ByWr8dBBzTv3VWFldkpfSTZ6dFU Post Insertion Checklist Annotated] 
'''Deorbit Preparation Checklist''' [https://drive.google.com/open?id=0ByWr8dBBzTv3TlFjbkx5cHRESHM Deorbit Preparation Checklist Annotated] 
'''Entry Checklist''' [https://drive.google.com/open?id=0ByWr8dBBzTv3UEFTZTFoUGVWRTA Entry Checklist Annotated] 
'''TAL Checklist''' [https://drive.google.com/open?id=1O-W9DkF_FL-rMSKTkKiKbVhRU6hWIuKk TAL Checklist Annotated]

The Caution and Warning System fault messages annotated file contain all the fault messages implemented in the last dev version of December 2020.

'''Caution and Warning System Fault Messages''' [https://drive.google.com/file/d/1jGN9hUCghZFc1HAo67Ys9LurQoJKul8J/view?usp=drive_link CWS Fault Messages]

'''DPS Dictionnary System Management limit indicators''' [https://drive.google.com/file/d/1S-twHAqNxY3eKt7vRJCdzaBLKH1GFsfv/view?usp=drive_link DPS Dictionnary SM Indicators]

From 230 pages for ascent FDF, we go to less than 30 pages. A huge amount of datas of those FDF are for non-normal situations. It was important to have a quick look to know what to do in case of Engine failure for example.
Ascent checklist is pretty straight forward, reading from up to bottom with time of actions, where to look ( panels R2, L2, O 14 etc), and what to do.

Sometimes, a square root √ is preceding an item. It means " check that ( monitor)". For example, ''√ Evap out=60°'' means Check that the evap out of the Freon is around 60°

A special note for Post insertion and Deorbit Preparation Checklists. It's a bit different than previous one.
In this one, Commander, Pilot, Mission Specialist are supposed to do differents things in the cockpit, so the checks can be a bit weird to read at first glance.
Here some hints:

On the left, there is the timeline of the mission, in Mission Elapsed Time since lift off. Panel where to look is also shown ( R2, O12, etc)

Also, C P or MS is used to define who will do the actions ( Captain, Pilot, Specialist). Obviously here, it's gonna be us

[[File:WWDMhj.png|1000px|thumbnail|none]]

 
You see for example at Star Tracker activation, there is a rectangle with a number ( 12) and a page number 1-6
It's gonna be where you have to look to have the full procedure, we are at page 1-7 so we have to go back one page before to have the procedure for Star Tracker activation.
Same logic for almost all the others actions with a rectangle and page reference at the right of the line.

[[File:WWDMhj.png|1000px|thumbnail|none]]

All those checklists contain a lot of informations and actions that are not critical for flight safety.
The ones to perform absolutely are present in game via Help menu and Checklist.

Some very usefull Screens, sum up of all shortcuts to navigate in differents parts of the GPC GNC and SM functions

[[File:DPS1.png|1000px|thumbnail|none]]

[[File:DPS2.png|1000px|thumbnail|none]]

Space Shuttle Avionics

2024-11-23T10:06:29Z

Gingin: /* Software Caution and Warning (CWS) */

{{DEFAULTSORT:Avionics}}
[[File:Canvasready.png]]
{{Space Shuttle navigation}}

The avionics of the [[Space Shuttle]] is designed to provide Guidance, Navigation and Control (GNC) through all phases of a mission as well as Systems Management (SM) functions. Like all systems aboard, it is designed with substantial redundancy in mind.

At the core of the avionics is the Data Processing System (DPS)<ref>http://history.nasa.gov/computers/Ch4-6.html</ref>. In interaction with the DPS, the crew can monitor the status of systems aboard, enter maneuvering targets for the autopilot, re-configure the Digital Autopilots, control mechanical systems such as the payload bay door and perform similar tasks.

In FlightGear, the front-end is primarily implemented using [[Nasal]] scripting and the [[Canvas]] system for 2D rendering purposes. Most of the code can be found in [http://sourceforge.net/p/fgspaceshuttledev/code/ci/development/tree/Nasal/PFD/ Nasal/PFD]. The display is using Richard's [[Canvas MFD Framework]] from the F15.

== Hardware overview ==

The DAP physically runs on a set of five General Purpose Computers (GPCs)<ref>http://history.nasa.gov/computers/Ch4-1.html</ref>. These are 1980 hardware, i.e. their performance and memory is limited, which means that no GPC ever runs the full set of avionics functions available, rather the functions are loaded as needed and distributed over the different GPCs.

The DPS information is displayed on the Multifunction Electronic Display System (MEDS), consisting of a set of nine multifunction display units (MDUs) at the front of the cockpit and two at the rear of the flightdeck. Three keyboards, two at the center console, one in the rear of the flight deck, allow to enter information, and edgekeys located below the MDU screens allow to change menu items.

== Software overview ==

There are two independently written software suites used aboard the Space Shuttle - the Primary Avionics Software System (PASS) and the Backup Flight System (BFS). The reason is redundancy - if PASS fails due to a software bug, BFS will always be available, as it is unlikely that an independently developed system will experience an identical fault.

There are three major functions the software loaded on a GPC can perform in PASS:

* Guidance, Navigation and Control (GNC)
* Systems Management (SM)
* Payload (PL), usually unsupported

In contrast, BFS combines all major function, but contains only a minimal support for critical functions. Usually the Shuttle should be operated using PASS only.

The standard arrangement is to run PASS GNC on three GPCs in synchronized mode such that any hardware failure does not affect operations, PASS SM on one GPS and run the BFS on the last available GPC.

Since the memory of each GPC is limited, what software is run is determined by the current Operational Sequence (OPS). Relevant here are ascent (OPS 1), on-orbit maneuvering (OPS-2), de-orbit, entry and landing (OPS 3), on-orbit operations (OPS 4) and RTLS abort (OPS 6).

Each OPS is sub-divided into so-called Major Modes (MMs) which are all available if the OPS is loaded and each display as a separate interface page. For instance, MM 304 is the entry phase whereas MM 305 covers TAEM and landing.

Under each MM, there may in addition be specialist functions (SPEC) and displays (DISP) available which can be brought over the current OPS screen.

=== Interaction with the avionics ===

The top level of what is displayed on-screen is the MEDS menu. Historically, the MEDS functionality has been added when the Shuttle fleet received glass cockpits, the CRT screen displays the first generation of Shuttles had is now sorted summarily under the DPS menu item in the edge-key controlled menu.

In general, the MEDS displays involve drawn symbology and visually easy to parse information, the DPS screens involve alphanumerics and hard to read, information-dense displays, often with the possibility to enter data.

Somewhat confusingly, MEDS display menu hierarchy is controlled via edge-keys, whereas DPS screens are called up by entering multi-key commands on the keyboard. To call an OPS screen, for instance 304 (entry) it's number has to be entered as the sequence OPS 304 PRO after the DPS menu item has been called via edgekeys. To access a SPEC or DISP screen, the number has to be entered preceeded by the SPEC key, i.e. SPEC 18 PRO calls up DISP 018, the GNC Systems Summary display.

In addition there are shortcut keys on the pad --- SYS SUMM always brings up the available systems summary pages and toggles between them if there are more available, FAULT SUMM brings up the fault summary display.

The same mechanism is used to instruct a computer to re-load software and make an OPS transition - the transition is initiated by calling the first major mode of a different OPS. For instance in de-orbit preparation, to end on-orbit operations and load the entry guidance software, OPS 301 PRO needs to be entered.

Usually OPS and SPEC pages allow interaction of the user with the system. This is done via calling numbered items on the screen. If an item can be executed, say item 5, the sequence is ITEM 5 EXEC. If an item needs to be set to a value, a delimiter key, '+' or '-' needs to be used (if the value can take positive and negative values, the delimiter key is actually meaningful). For instance, ITEM 5 + 30 EXEC sets item five to the value of +30.

=== Choosing a screen ===

The forward panel of the Shuttle has nine MDUs with two keyboards available, and as mentioned above there are five GPCs running. So which GPC is affected when a command is typed and which screen shows it?

The connecting element between MDUs, GPCs and the keyboards are the integrated display processors (IDPs). There are three IDPs responsible for the forward panel. Each keyboard talks to an IDP, each IDP monitors the GPCs either for SM or GNC tasks, and each MDU is connected to at least one IDP (possibly two) via a primary and a secondary port.

For instance, the left-most screen of the commander (CDR1) is connected to IDP 3 via the primary (normally chosen) and IDP 1 via the secondary port. Since figuring out the connection isn't straightforward, a box with the IDP currently responsible for the screen is displayed in the lower part of the screen whenever a DPS page is selected. Dependent on which keyboard is currently connected to the IDP, colored bars are also displayed. A red bar extending to the left indicates that the left (Commander-side) keyboard is talking to the IDP, a yellow bar to the right indicates that the Pilot-side keyboard is active. For IDP 3, it is possible to have both keyboards talking to the same screen, in which case you can type command sequences affecting the IDP from both sides.

[[File:IDP_selection.jpg|256px|IDP indicator box and keyboard bar of the Space Shuttle DPS]]

Thus, to use GNC functionality on this screen from the Commander's seat, it is necessary to

* select DPS MENU via the edgekeys
* switch the IDP 3 to GNC
* switch the left keyboard to talk to IDP 3

Then it is possible to work on the screen as described above. The IDP automatically picks one of the GPCs that runs the requested major function to communicate with. The GPC number currently accessed via the DPS screen is indicated in the top line of the screen (for instance, since SM by default runs on GPC 4, you'll see a 4 there whenever you use SM functionality).

To access SM rather than GPC functionality, the IDP controlling the screen needs to be switched to SM. A schematic of how IDPs and MDUs are connected is given in the crew manual on page 2.6-16.

Note that keyboard commands will affect all screens connected to the IDP in question as long as DPS MENU is selected for them.

=== Software Caution and Warning (CWS) ===

While critical systems all have a hardware fault detection and never rely on software running, less important systems send backup warning messages to the software in case of off-nominal situations.

These appear as red flashing messages below the DPS display in the so-called fault line. In case of multiple faults, only the latest message is displayed. Pressing MSG ACK once on the keypad ends the flashing of the message and allows to inspect it, a second press clears the fault line and brings up the next message from the stack (if there is any). A record of the last 15 fault messages is kept in the FAULT display (DISP 99), see below.

C/W messages may include a pointer to the utility function which allows to inspect the problem in more detail. Users should consult the Space Shuttle Crew Operations Manual for the procedures to deal with faults beyond acknowledging the message.

The complete fault messages available in Sim are summed up there ( December 2020):

[https://drive.google.com/file/d/1jGN9hUCghZFc1HAo67Ys9LurQoJKul8J/view?usp=drive_link CWS fault messages]

=== MEDS fault messages ===

The MEDS system produces its own set of fault messages which only deal with failures of the MEDS system itself, not with problems elswhere in the Shuttle. These are displayed in the lower portion of the display, above the title of the current menu page.

Like the CWS messages, they need to be acknowledged, can be deleted from the line, and are available as a summary on the IDP FAULT SUMMARY page. However, unlike the CWS messages, they are not acknowledged by keyboard entries but by edgekey options.

MEDS messages are specific for one IDP and are preferentially shown on any DPS screens this IDP commands. Any MDU not commanded by the IDP which has detected the fault will not show the message in either the fault line or its summary page.

As the following example shows, it is possible to have CWS and MEDS fault messages on-screen simultaneously.

[[File:MEDS_error_message.jpg|600px|MEDS menu layer of the Space Shuttle avionics]]

=== Illegal entry ===

When the DPS receives an input it cannot parse, it will reject it and write a message to the fault line. This can have a number of reasons which all require a different user response.

* The message is not properly formatted. For instance, ITEM 8 PRO is not valid syntax, PRO closes an OPS or SPEC command, not an ITEM. Check the syntax of the entered string.

* The selected item may not be legal in the current major mode / OPS. In general, the software cannot perform all possible functions in all phases of the flight. For instance, the DAP configuration utility (SPEC 20) is not available during ascent (OPS 1) or entry (OPS 3) and a request to bring it on screen under these conditions will be answered by 'Illegal entry'. Please refer to the DPS dictionary whether the operation you want to perform is legal in the circumstances.

* The selected item may not be supported in FG in spite of being supported in reality. Not all functions of the software are, please refer to the descriptions of the screens below which outline what functions of a display work in FG.

=== Data transmission errors ===

There are two special situations in which non-standard screens appear - an IDP may lose communication with a GPC and hence be unable to display DPS screens, and an MDU may lose contact with its driving IDP and hence not be able to display any information.

If the IDP cannot exchange information with a GPC, the DPS part of the screen appears crossed out to signal that it is no longer updated. In addition, the MEDS system throws a POLL ERROR message.

[[File:Poll_fail.jpg|600px|DPS screen with IDP poll error]]

This can happen in two ways: Either there is no GPC available to support the requested major mode (for instance, in nominal launch configuration, no GPC runs system management software and hence any request to show SM DPS screens via the major mode switches leads to the error (since usually three or four GPCs run GNC software, it's unlikely that no GPC out of that redundant set of available).

The other possibility is that the GPC was intentionally isolated using the GNC/CRT key by assigning GPC 0 to the IDP (GPC/CRT 03 EXEC to do this to IDP3).

The situation is resolved by either making a GPC with the requested major function available or by re-connecting the GPC to the IDP in question using the key command.

If an MDU cannot reach an IDP at all, it goes into autonomous mode:

[[File:Shuttle avionics autonomous.jpg|600px|Autonomous Shuttle MDU]]

Basically the only thing it can try to do is to change ports, and the menu reflects this. If the reconfiguration mode is set to AUTO, the port change is tried automatically, and you may see the failure only as a PORT CHANGE message.

This situation can arise if you accidentially switch an IDP off or if it fails. The situation should be resolved by re-configuring ports such that the MDUs are driven by the functional IDPs as much as this is possible,

== MEDS screens available ==

The MEDS screens are selectable via the display edge keys under their respective submenu.

=== A/E PFD ===

The primary flight display provides a summary of all GNC relevant parameters. Its core is the ADI ball on which the attitude of the Shuttle in the selected coordinate system is shown, surrounded by tapes for velocity, alpha, altitude and vertical speed. In the lower half, an accelerometer and the course deviation indicator are provided along with mission-phase specific alphanumerics.

Error needles on the ADI ball provide 'fly to' indicators based on the current guidance computations which can be used when piloting the Shuttle in CSS mode.

The PFD is a complicated instrument in which the meaning of various readings depends on switch settings and mission phase (for instance, the ADI reference can be standard pitch/heading/roll as for an aircraft in the final phase of the flight as well as inertial or LVLH in orbit; the range of the error rate display is also selectable, the accelerometer will show Nz during entry and TAEM rather than linear acceleration during launch,...) - so make sure you understand what it is showing before using its information.

Most of the original functionality is implemented in FG.

As stated above, PFD is complex and informations displayed on it differ quite a lot depending of the phase of flight and abort mode.

A complete explanation about that is available in [https://www.nasa.gov/centers/johnson/pdf/359895main_DPS_G_K_7.pdf DPS dictionnary Section 6].

We will go through the different modes implemented so far ( Dev version December 2020).

Major Mode 101 ( before SSME Ignition)

ADI is driven by nav software 4 mn before launch

[[File:Mm101.jpg|600px|PFD of the Space Shuttle in MM101]]

SRB ignition , MM 102

[[File:Mm102.jpg|600px|PFD of the Space Shuttle in MM102]]

SRB sep, MM 103

Beta and Vrel pointer (relative velocity) vanished above 200 kfeet

[[File:Mm103.jpg|600px|PFD of the Space Shuttle in MM103]]

In case of TAL declared, MM 103 T.

Now, distance to TAL runway and bearing is displayed , some other informations are removed.

[[File:Mm103tal.jpg|600px|PFD of the Space Shuttle in MM103 TAL]]

External Tank separation, MM 104.

[[File:Mm104.jpg|600px|PFD of the Space Shuttle in MM104]]

PFD MM105 through 303 is normally just displaying the ADI ball.
However, some relevants informations were kept for On orbit better management ( rendez vous, ...)

[[File:Mm105.jpg|600px|PFD of the Space Shuttle in MM105 through MM 303]]

Entry mode now, MM 304 or MM 602.

New layout for Pitch and Roll/yaw Auto or CSS and speebrake shown now below MM on the right ( Yellow rectangle when switched to Manual or CSS above mach 1).

Also HAC bearing and runway distance only displayed, with vertical acceleration.

[[File:Mm_304_602.jpg|600px|PFD of the Space Shuttle in MM304]]

TAEM interface ( mm 305 or 603)

Heading Alignement Cone (HAC) H pointer for WP1 (entry in the HAC) and C for HAC center.

Both distance to runway and to HAC center are displayed.
Glideslope only and no vertical acceleration displayed anymore.

[[File:Mm_305_603.jpg|600px|PFD of the Space Shuttle in MM305]]

Entering the HAC.

DAz (Delta Azimuth) is replaced by HTA ( Hac turn angle). It displays remaining degrees in HAC before runway alignement.

[[File:Entering_hac_HTA.jpg|600px|PFD of the Space Shuttle in MM305 entering the HAC]]

Once in final Approach Landing mode (A/L), the only things remaining are Runway Bearing and Distance to Runway

[[File:AL_305.jpg|600px|PFD of the Space Shuttle in MM305 entering A/L]]

Below Mach 0.9, Speed tape switches to EAS ( with still mach ladder behind) and Speed box switches to Mach.

Yellow Altimeter tape below 2000 feet ( either AGL or Baro depending if Radar altimeters are available or not).

[[File:Subsonic_mm_305.jpg|600px|PFD of the Space Shuttle in MM305 Subsonic]]

A special Abort mode that changes a bit the different layouts.

If RTLS declared, MM 601.

Vrel pointer and Beta display appeared again.

Pre Pitch Power Around (PPA), Inertial Speed is displayed.
Post PPA, Relative Speed is displayed and Bearing to runway with Earth relative tail pointer.

MM 601 Pre PPA

[[File:Mm_601_pre_ppa.jpg|600px|PFD of the Space Shuttle in MM601 pre PPA]]

MM 601 Post PPA

[[File:Mm_601_post_ppa.jpg|600px|PFD of the Space Shuttle in MM601 post PPA]]

=== ORBIT PFD ===
{{See also|Shuttle ADI ball}}

[[File:Orbit_pfd_december_2020_HD.jpg|600px|PFD ORBIT display of the Space Shuttle]]

In orbit, the PFD has a special mode accessible via the edge keys which shows only the ADI ball and suppresses all other gauges and scales (which are not particularly meaningful for orbital operations anyway).

=== OMS/MPS ===

[[File:OMS_MPS.jpg|600px|OMS/MPS MEDS display screen of the Space Shuttle]]

On the OMS/MPS status display, a quick overview over the function of the engines can be gained. The display shows the tank pressure of the Helium and N2 systems, Helium regulator pressure for the MPS and the engine chamber pressures for all engines.

If any quantity takes an off-nominal value, the bars change color to red.

All values are meaningful in the context of the FG simulation.

=== APU/HYD ===

[[File:HYD_APU.jpg|600px|APU/HYD MEDS display of the Space Shuttle]]

To monitor the correct working of the three APUs and the hydraulic systems, the APU/HYD screen is used. It shows quantities of hydrazine fuel, coolant water and hydraulic fluid as well as hydrazine tank pressure, APU oil temperature and hydraulic pressure.

Any off-nominal values change the bars to red.

Except for the hydraulic fluid quantity (leaking of fluid is not yet simulated) all values shown are meaningful in FG.

=== SPI ===

[[File:SPI_december_2020.jpg|600px|SPI MEDS display of the Space Shuttle]]

The surface position indicator display shows the movement of the airfoils during the aerodynamical part of the flight. It can for instance be used to check how close, dependent to trim, the elevons are to saturation or how stable the spacecraft is.

(Note that since the Shuttle control surfaces are not driven by the stick but by a digital autopilot which takes the stick input as target, it is near impossible from the feedback to control inputs to gauge whether e.g. trim is off or not, so monitoring the display to ease the trim load of the elevons via body flap and/or speedbrake is important.)

=== MEDS MAINT ===

[[File:MEDS_maint.jpg|600px|MEDS MAINTENANCE display of the Space Shuttle]]

The MEDS maintenance display shows the current status of the display setup. For each MDU, a box shows connected ports, flight-critical buses, port reconfiguration mode and self-test results. For each IDP and ADC (analog-digital converter) self-test results are available.

Various submenus of the page allow to change ports, allow to change port re-configuration and are used to initiate self-tests (currently not implemented).

Note that the page is always constructed from the point of view of the IDP in command of the screen and hence displays only information known to this IDP (i.e. MDUs which are not connected to the current IDP via either primary or secondary port can not be accessed).

=== IDP FAULT SUMMARY ===

[[File:Meds_fault_summary.jpg|600px|IDP FAULT SUMMARY display of the Space Shuttle]]

The IDP fault summary (one exists for every IDP, the one shown is always of the IDP in control of the screen) is a sub-page of the MEDS maintenance page and shows a summary of all the fault messages of the MEDS system and allows to clear the list.

Note that MEDS fault messages are a category different from DPS faults generated by the software caution and warning system- this display will not show any faults in systems outside the display system itself, general faults are shown on DPS SPEC 99.

== GNC DPS screens available ==

The following section gives a rough overview of the DPS screens which are currently available for guidance, navigationand control functionality in FG. For detailed information on what the displayed parameters are and what their meaning is, refer to the [https://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf Space Shuttle Crew Operations Manual]

=== ASCENT TRAJ 1 (OPS 101 and 102) ===

[[File:Mm_102_final.jpg|1200px|ASCENT TRAJ 1 display of the Space Shuttle]]

This screen is almost as accurate as the original. It shows the vertical situation during the ascent - the central section is a plot of altitude vs. relative speed and the line is the planned ascent trajectory. If the Shuttle symbol moves above the line, it means the climbing angle is too steep and the spacecraft is too high for its velocity, if it falls below it means the ascent is too shallow. A predictor circle shows the anticipated state of the spacecraft 20 seconds in the future assuming no changes in attitude or throttle occur. This allows to plan the ascent path when flying manually.

In addition, SSME throttle setting is displayed.

=== ASCENT TRAJ 2 (OPS 103) ===

[[File:Mm_103_final.jpg|1200px|ASCENT TRAJ 2 display of the Space Shuttle]]

This screen becomes visible during the second part of the ascent (after SRB separation). It is an accurate version of the original (PASS and BFS) and shows the same vertical situation as the previous screen, but at different scales. In addition, it offers information in throttle setting and remaining propellant. The inertial speed scale is magnified from 25.000 to 26.000 ft/s in the upper part of the screen and shows the anticipated point of main engine cutoff (marked by CO).

Predictor circles show the anticipated state of the Shuttle assuming no changes in attitude and thrust occur for 30 s and 60 s in the future. This allows to aim to near ballistic climb onto the correct trajectory when flying manually.

=== MNVR (OPS 104, 105, 202, 301, 302, 303) ===

[[File:Ops_201_final_gnc.jpg|1200px|MNVR EXEC display of the Space Shuttle]]

With this screen, orbital maneuvering is controlled. Changes to the current orbit can be entered as so called Powered Explicit Guidance (PEG) targets, and when the target is loaded, the guidance computes automatically burn attitude, duration and the resulting changes to apoapsis and periapsis. The Shuttle can then be instructed to maneuver automatically into burn attitude and fires the OMS engines when the EXEC key on the pad is pressed as soon as attitude is reached and an EXEC symbol is flashing.

December 2020 dev version:

There is support for both PEG 7 and [http://www.science-and-fiction.org/science/leo_05.html PEG 4], and the timer is available - the rest of the items is fully functional.

=== UNIV PTG (OPS 201) ===

[[File:Ops_202_final.jpg|1200px|UNIV PTG display of the Space Shuttle]]

Using the maneuver screen, the attitude of the Shuttle can be automatically controlled. Various options are available, ranging from specifying an inertial yaw/pitch/roll to selecting a body axis and pointing this body axis automatically towards a target (the Sun, Earth, a location on Earth,...).

Most of this display is functional, except the timer is not available, the body axis cannot be configured and no other spacecraft or stars are available as tracking targets.

=== ENTRY TRAJ 1 (2,3,4,5) (OPS 304) ===

[[File:Full_entry_traj.jpg|1200px|ENTRY TRAJ 1 through 5 display of the Space Shuttle]]

During entry, the ENTRY TRAJ display series is used to control the deceleration for successful range management to arrive at the desired TAEM interface. The series consists of five displays, all of them showing range to go on the x-axis vs. inertial speed on the y-axis - if the Shuttle symbol is above the desired trajectory, it is too fast and needs to establish a higher sinkrate (higher bank angle) to decelerate more, if it is below the sinkrate needs to be reduced. In addition, the display also shows Delta Azimuth for planning roll reversals and the current values of deceleration and dynamic pressure qbar. To display a meaningful range, a landing site needs to be selected and entry guidance needs to be active, otherwise the avionics does not know where the Shuttle is aimed.

The implementation in FG is now accurate ( January 2021 dev version).

=== VERT SIT 1 (2) (OPS 305) ===

[[File:Shuttle avionics ops305.jpg|600px|VERT SIT 1 display of the Space Shuttle]]

To manage the Shuttle's energy as a function of range to the runway during TAEM, the VERT SIT 1 and 2 displays are used. They show a Shuttle symbol in comparison with a trajectory which displays altitude on the y-axis and range to touchdown on the x-axis. If the Shuttle is above the nominal trajectory, it is high on energy, if it is below it is low. Two limit trajectories are also shown - the left-most trajectory corresponds to the case of extending speedbrakes to 100% and flying the Shuttle close to the qbar limit, i.e. the fastest energy dissipation possible. The right-most trajectory is based on keeping the Shuttle on the optimum glidepath. Numbers indicate the KEAS values that need to be flown for the trajectories.

TAEM guidance needs to be available for the display to have any meaning, since the distance to touchdown is not a direct distance but includes the circle around the heading alignment cylinder (since the difference can be up to 20 miles, this is not a small correction).

The display is kept largely similar to the original version but does not display the automatic flight control settings of the real Shuttle since the FG version is supposed to be piloted during TAEM and has no routines for automatic aerodynamical flight.

=== RTLS TRAJ 2 (OPS 601) ===

[[File:Ops_6_final.jpg|1200px|RTLS TRAJ 2 display of the Space Shuttle]]

For the powered stage of an RTLS abort, this display provides a set of sample trajectories to guide maneuvering. It is a representation of horizontal velocity component against altitude with a zero line in the center, i.e. at the left end of the display, the Shuttle is flying back to the launch site.

A set of predictors estimate the future state of the Shuttle, and the display also allows to read the remaining propellant, throttle setting and to activate single engine roll control (SERC).

=== GPC MEMORY (SPEC 0) ===

[[File:Spec_0_final.jpg|1200px|GPC MEMROY utility display of the Space Shuttle]]

The GPC memory display is the base layer of the Shuttle software - it is what is available after a GPC has been moded to RUN. Consequently it is used to determine what application software the GPC should load.

This is done in two possible ways. A whole configuration for an OPS sequence can be edited using items 1 to 19 - GPCs can be assigned to a major function, to control the various data buses and to be in charge of an IDP (here called CRT for historical reasons). The assignment is then automatically executed once the OPS transition is called.

Alternatively, a single GPC can be assigned a software configuration right now using items 45 to 47. In this way, for instance systems management can be made available in OPS 1 by loading SM software into one GPC (which is not nominally done).

The rest of the display is in reality used for memory dumps, displays of actual memory content at a given address and similar things, however these items are not implemented in FG.

=== TIME (SPEC 2) ===

[[File:Spec_2_final.jpg|1200px|TIME utility display of the Space Shuttle]]

The time utility display is responsible for how time is displayed in the generic DPS display mask. It allows to switch between GMT and MET (mission elapsed time), to define a CRT timer which can count independently of the global timer, to set three alarms (two on MET, one on CRT time) and to arrange for a count-down of time to a specific MET in the upper third.

The middle third of the display allows to define offsets for MET and GMT (the latter only in maintenance mode, not supported by FG) which allows to for instance set the displayed time to any timezone desired. The remaining portion of the display is technical and manages the time synchronization between the master timing units (MTUs) and the GPCs. The display is only available in OPS 2.

The FG version supports the setting of alarms and managing MET and CRT time, but since time synchronization is not explicitly simulated, the lower portion of the display is non-functional.

=== GPC/BUS STATUS (DISP 6) ===

[[File:Spec_6_final.jpg|1200px|GPC/BUS STATUS utility display of the Space Shuttle]]

The GPC and bus status utility display contains an overview over the software configuration currently running. For each of the five GPCs, the current status (run, standby or halt) is shown along with the application software loaded (G for GNC, S for systems management, the number represents the OPS sequence.

Below is a summary which GPC is in command of which data bus and which GPC is communicating with which IDP (on this screen called 'CRT' - this is a legacy designation from the old Shuttle cockpit when a GPC was directly linked to a CRT screen).

=== DAP CONFIG (SPEC 20) ===

[[File:Spec_20_dap_final.jpg|1200px|DAP utility display of the Space Shuttle]]

Using the DAP configuration, the maneuvering characteristics of the Shuttle in orbit can be customized. Both DAP-A and DAP-B can be accessed, as well as pre-loaded alternative configurations for both can be retrieved from memory or edited (the latter is not implemented in FG).

The utility allows to set for both primary and Vernier thrusters the rotation rates the controller aims to achieve when in a 'stick controls rates' scheme, the effect of a single stick movement ('pulse') for both translation and rotation when in a 'stick controls thruster' scheme, the deadbands for the rates and the deadbands for attitude hold modes.

In addition, various other options allow to (de-)select forward or aft thruster pods or to ask for compensation for mode-mixing when maneuvering.

=== IMU ALIGN (SPEC21) ===

[[File:Spec_21_IMU_final.jpg|1200px|IMU align display of the Space Shuttle]]

This display allows to have access to Inertial Measurement Unit state.

Top left part is used to deselect an IMU if a dilemma or overheat is detected.

Top right part is the align option available. All begin with the Star Trackers that will be pointed to two known Stars inertial position wise ( Real Present Position). It will be then compared to the Current Position ( the one estimated by the IMU). The delta will be shown on the bottom left next top Delta X,Y and Z. That delta represents the drift of the IMU's compared to the real Shuttle position given by the Star Trackers feedback.

Torque will move (3D rotation) the IMU to zero the delta position and Matrix will just change the conversion Matrix without torquing the IMU ( usually not use as it might lead to one or more IMU in an Euler singularity at the same time in the future).

Both options lead to the same consequence: IMU will be re aligned and State Vector health will be positively increased.

=== S TRK/COAS CNTL (SPEC 22) ===

[[File:Spec_22_strk_final.jpg|1200px|STRK/COAS display of the Space Shuttle]]

On the star tracker / COAS control display, two of the attitude sensors of the Shuttle can be operated.

The left half displays star tracker control and data and allows to select the various operation modes of the star tracker (upper half) as well as outputs the current state of the two trackers, whether a star is in the field of view, what the star ID is and what the angular deviation with respect to the database is.

The upper right displays a history of the last three stars which have been tracked (the 'star table') which can serve as input for navigation calculations.

The crew optical alignment system (COAS) is used when the Shuttle has drifted so much out of attitude that the tracker no longer operates correctly. It allows to select a star ID, switch the position of the COAS frame, accept a mark and forward a combination of two COAS marks for processing.

All displayed fields and items except the COAS calibration are meaningful in FG, and COAS procedures can be executed for a subset of 10 stars.

=== RCS (SPEC 23) ===

[[File:Spec_23_RCS_final.jpg|1200px|RCS display of the Space Shuttle]]

The RCS display page is used to monitor and manage the state of the RCS thrusters as well as (in a limited way) the propellant flow. For each individual thruster, its current state (i.e. whether it is operating normally, failed leaking, failed OFF i.e. refuses to ignite or failed ON i.e. refused a shutdown command), whether it is selected to be used and its priority in the jet table is shown.

In addition, propellant pressures and temperature along the feedlines and manifolds are displayed. The upper part of the display allows to set some general options and monitor the OMS to RCS interconnect fuel usage.

The display works in such a way that items 1-3 are used to select the RCS thruster pod, and all displayed information and all entered items then refer to this pod.

In FG, most of the displayed information is meaningful and corresponds to the internal state of the Shuttle. In particular, de-selected jets will not be used by the DAP, and jets failed on need to be extinguished by cutting the propellant flow and de-selecting the jet from the table.

=== RM ORBIT (SPEC 25) ===

[[File:Spec_25_rm_final.jpg|1200px|RM ORBIT display of the Space Shuttle]]

The orbit redundancy management display is used to check (and if necessary) deselect the transducers of the various control sticks - the two forward and one aft rotational hand controller (RHC) and the forward and aft translational hand controller (THC). Whenever a controller is moved, it shows the signal picked up by the transducers.

In FG, since no transducer failures are modeled, this is basically an interesting way to check your joystick settings. The display shows whatever your equipment currently generates as signals in yaw, pitch and roll channel, and dependent on selected DAP and your view position this is assigned to one of the physical Shuttle controllers.

=== REL NAV (SPEC 33) ===

[[File:Spec_33_final.jpg|1200px|REL NAV display of the Space Shuttle]]

The REL NAV display is used for rendezvous and proximity operations to snow the relative position to a rendezvous target. It's a fairly complicated display which requires some knowledge on the theory of space navigation and state vector management to properly understand and operate.

Assuming ideal navigation, only the column of numbers below SV SEL are important, where range, approach rate, angular orientation, displacement along the angular momentum axis of the target and approach rate along the angular momentum axis (assumed to be the desired docking direction) is shown.

The rest of the display is used if the state vectors of Shuttle and target are not perfectly known and have errors. In this case, radar ranging (RR) can be used to directly measure distance and approach rate and various filters based on other sensors can be utilized to improve upon the computed state vector.

Many options are at least semi-quantitatively implemented in FG, i.e. filters will show residuals which allow to gauge their quality and can be used to update the state vectors, but there's no real simulation of the filter matrix done, the simulation just assigns a filter quality measuring how close to the true state of the craft a filter leads.

=== ORBIT TGT (SPEC 34) ===

[[File:Spec_34_final.jpg|1200px|ORBIT TGT display of the Space Shuttle]]

While usually mission control would perform such tasks and uplink the results, the Shuttle has an on-board computer for calculating burn sequences to reach orbital targets. This functionality is controlled via SPEC 34.

The display allows to compute a sequence of two OMS burns (T1 and T2) that will bring the Shuttle close to a target such that rendezvous navigation (SPEC 33) can be used (the difference being that SPEC 34 assumes you are far from the target and orbital mechanics effects are important to reach it, while SPEC 33 assumes you are so close to the target that translational RCS burns are all that is needed).

In addition, in the lower right corner, the current state vector of the Shuttle as known by the avionics is displayed.

As of December 2020, the implementation in FG supports a quasi-Hohmann transfer computation. From a lower, reasonably circular orbit, item 28 calls a numerical trajectory solver which fits burn parameters to reach the target. The results are stored as PEG-7 targets and can directly be used in the MNVR display.

=== HORIZ SIT (SPEC 50) ===

[[File:Spec_50_final.jpg|1200px|HORIZ SIT display of the Space Shuttle]]

With a somewhat misleading designation, the HORIZ SIT display is actually the central managing display for the landing site selection and area navigation, and only in addition to that it provides a horizontal view of the TAEM guidance.

The upper left is used to enter the landing site and choose the runway. Below the TAEM pattern is specified, i.e. whether to fly and overhead or straight-in approach and whether to use nominal or minimal entry point. The right portion of the display allows to enter navigation corrections manually. Finally, the lower portion contains the navigation data management during entry and TAEM - it shows the various sensors (TACAN, GPS, drag altitude, air data probe altitude), their residual with respect to the currently used state vector and their usability ratio as well as the target azimuth and target range obtained by using the respective sensor.

Finally, the graphical portion shows the heading alignment cone (HAC), the final approach and the touchdown point as well as predictors of the Shuttle position 20, 40 and 60 seconds into the future which allow to aim the trajectory properly onto the HAC.

Most of the items are meaningful in FG, in particular every sensor is characterized by a quality with respect to the currently propagated and the true state vector.

=== OVERRIDE (SPEC 51) ===

PASS display

[[File:Spec_51_final.jpg|1200px|OVERRIDE PASS display of the Space Shuttle]]

BFS display

[[File:Spec_51_bfs_final.jpg|1200px|OVERRIDE BFS display of the Space Shuttle]]

The purpose of the override display is to manage off-nominal situations. In particular, this includes software backups for failed hardware switches in the cockpit and reversing decisions of automated recognition of failed systems.

The display allows to select TAL or ATO [[Flying_the_Shuttle_-_Abort_Procedures|abort procedures]], set the throttle control mapping, set the parameters and initiate OMS and FWD/AFT RCS fuel dumps, set various control parameters for the entry DAP, to deselect input from failed IMUs, to override the decision of the flight computer to declare a hydraulic system failed, to monitor air data and deselect input of failed or suspicious air data probes and to by-pass failed switches for ET separation, umbilical door control, vent doors and roll mode selection.

As such, the display is used both during launch and entry and not all items are legal in all major modes.

In FG, currently only abort mode selection, throttle control, fuel dumps and ET separation, umbilical and vent door control are fully implemented, the air data section is partially functional (i.e. items are displayed but air data is not explicitly used by navigation) and the rest of the display can not be used.

=== BEARING (SPEC 54) ===

It is a display that was available in the latest Shuttle software update (OI-33) which debuted with STS-126: https://www.nasaspaceflight.com/2008/10/126-debut-oi-33-rco-ability/

It helps with situational awareness for Ascent, Entry and ECAL aborts.
Only the Entry part of the Spec 54 is supported for now.
Not too much datas about it.
Here are the informations about the display coming from the OI-33 update at the end of the latest SCOM.

[[File:SCOM spec54.webp|600px]]

*Three items are available for crew inputs in Spec 54 display (item 41, 1 and 2).
Item 41 will choose the targeted site (and it will update the Entry guidance accordingly).
Item 1 and 2 will allow to select the alternate sites to assess the range / delta azimuth / energy condition.
[b]To use those latest items, the alternate site mode must be activated in OPS 304 display (item 4)[/b] (Red arrow).
Two rings with some range indications in Nautical Miles are displayed (4000 / 2000 / 1000 / 500 / 250 / 125).
A white azimuth line links the Shuttle symbol to the targeted landing site.

Pink arrows show the relative position of alt sites on spec 54 and the Shuttle energy status alt sites wise in OPS 304.

[[File:Entry spec54.webp|600px]]

*Roll reversal lines are displayed to indicate when the Shuttle should roll in the opposite direction for crossrange consideration.
Dashed lines are for 10 degrees roll reversal and plain lines are for actual roll reversal logic (10° or 17°).
First roll reversal will be done at 10° of delta azimuth (left picture).
Then up to mach 4, roll reversal will happen at 17° of delta azimuth (plain lines "open" in the middle picture).
Below mach 4, roll reversal will happen at 10° of delta azimuth again (right picture).

[[File:Deltaz spec54.webp|600px]]

*Shuttle symbol will bank according to real bank experienced.

[[File:Bank spec54.webp|600px]]

*An overbright blank “+” is also displayed off the nose of the orbiter representing the instantaneous impact point (iip). It represents where the Shuttle would end if nothing was changed to the L/D profile (ie. Shuttle bank roughly).

[[File:Iip spec54.webp|600px]]

=== GNC SYS SUMM 1 (DISP 18) ===

[[File:Sys_sum_up_1_final.jpg|1200px|GNC SYS SUMM 1 PASS display of the Space Shuttle]]

This display gives an overview over the state of the maneuver-critical systems, i.e. RCS thrusters and aerosurfaces. All items are meaningful and show various implemented failure modes if applicable.

The display changes a bit for the BFS part, where more informations regarding the Main Propulsion System are added ( Helium subsytems, Pressure of H2 and O2, Gaseous parameters for O2 and H2 that go from the engines to the tanks to pressurize them)

[[File:Sys_sum_up_1_bfs_final.jpg|1200px|GNC SYS SUMM 1 BFS display of the Space Shuttle]]

=== GNC SYS SUMM 2 (DISP 19) ===

[[File:Sys_sym_up_2_final.jpg|1200px|GNC SYS SUMM 2 display of the Space Shuttle]]

This display gives a detailed overview over the RCS and OMS systems, in particular propellant and oxidizer quantity, various pressure readings, valve settings etc. All items are meaningful and show the expected changes when the systems are operated or when simulated failure modes occur.

=== FAULT (DISP 99) ===

[[File:Fault_summary.jpg|1200px|FAULT display of the Space Shuttle]]

The fault summary display shows a historical record of the last 15 fault messages produced by the caution and warning software system, These are only visible if the display is called up using the FAULT SUMM key but they are erased if SPEC 99 PRO is used to access the page.

All information of this display is meaningful as far as the CWS fault detection is implemented.

== SM DPS screens available ==

The following screens of the systems management software are available:

=== ANTENNA (OPS 201) ===

[[File:Ops_201_sm_final.jpg|1200px|ANTENNA display of the Space Shuttle]]

Using the antenna display, both the Ku-band and S-band antenna operations can be monitored and controlled. For both Ku and S modes tracking the TDRS satellite network are available, using the displayed TDRS state vectors. A primary pointing target can be assigned and is used by the GPC to direct the Ku antenna towards the chosen satellite.

The S-band antenna can connect with both ground stations and the TDRS network. In ground mode, the display shows the station currently in reach as well as what quadrants of the antennas are used. In TDRS mode, a pointing target for forward and return link is chosen similar to the Ku operation.

=== PL BAY DOORS (OPS 202) ===

[[File:Ops_202_sm_final.jpg|1200px|PL BAY display of the Space Shuttle]]

The payload bay door management display is an operational sequence of the systems management functionality used in orbit. It allows detailed software control over opening and closing the payload bay door latches and doors and monitors the state of the individual microswitches leading to 'open' and 'closed' talkbacks.

In particular, it also allows to drive the opening sequence manually rather than automatically and has a software bypass implementation for the case of a failed main payload bay door switch. All functions of the original screen are implemented in FG.

=== ENVIRONMENT (DISP 66) ===

[[File:Spec_66_env_final.jpg|1200px|ENVIRONMENT display of the Space Shuttle]]

The crew monitors the cabin environment - atmosphere, water, temperatures - on DISP 66. The various sections show (clockwise from upper left): 1) Cabin atmosphere with pressure, partial pressure of O2, fan action and pressure change. 2) Avionics bay fans and temperature readings 3) supply water quantities, tank pressures and exhaust line and vent temperatures 4) waste water quantity, pressure and vent temperature, 5) regenerable CO2 removal system status (this is not installed on 'Atlantis') 6) IMU fan and humidity separator status and 7) oxygen and nitrogen system pressures, flows and valve status.

With the exception of waste water quantity, all parameters on the display are real in FG, i.e. simulated in some way. In particular, the simulation of cabin atmosphere is rather faithful.

=== ELECTRIC (DISP 67) ===

[[File:Spec_67_electric_final.jpg|1200px|ELECTRIC display of the Space Shuttle]]

On this display, information on the power consumption and distribution throughout the Shuttle can be found. It shows the voltages measured at the main DC and AC buses as well as the current flowing through the systems and the total consumption of all systems aboard the orbiter.

Almost all data displayed (except the detailed distribution across the forward, mid and aft distribution assemblies) is meaningful and reflects the systems running aboard the Shuttle as well as the position of the bus connector and tie switches.

=== CRYO SYSTEM (DISP 68) ===

[[File:Spec_68_final.jpg|1200px|CRYO SYSTEMS display of the Space Shuttle]]

Cryogenic stores of hydrogen and oxygen are carried aboard the Shuttle both to provide reactants for the fuel cells and to provide water for the environment system. The state of the cryogenic tanks (temperature, pressure and quantity) can be monitored via the cryo system display.

Most of the data displayed in FG is generic as there are no failure modes for the cryo system implemented, i.e. it is assumed that temperatures and pressures are always nominal. The only non-trivial reading is the quantity of the stores.

=== FUEL CELLS (DISP 69) ===

[[File:Spec_69_FC_final.jpg|1200px|FUEL CELLS display of the Space Shuttle]]

The fuel cells display shows data on the electrical power generation aboard the Shuttle. It allows to monitor power output of the fuel cells, reactant consumption, stack temperatures and the function of the cooling pumps as well as temperatures of relief lines and purge lines and contains a detailed substack diagnostics monitoring system.

Almost all entries except the pH monitors are meaningful in FG and accurately reflect various possible failure modes.

=== COMMUNICATIONS (SPEC 76) ===

[[File:SPec_76_comm_final.jpg|1200px|SPEC 76 Communications display of the Space Shuttle]]

A display that shows the status of the different means of communication in the Shuttle ( Ku/S Band, UHF, ...).

Some failures are implemented, like low temperatures if no heaters powered and lack of datas if communication not established with a realy station for example.

=== SYS SUMM 1 (DISP 78) ===

[[File:Sm_sys_sum_up_1_final.jpg|1200px|SM SYS SUMM 1 display of the Space Shuttle]]

The first SM systems summary contains an overview of the electric power generation and distribution as well as the readouts of the cabin environment system and smoke detection.

As of December 2020, all the parameters are implemented and showing subsystems real state (even the smoke in the cabin).

=== SYS SUMM 2 (DISP 79) ===

[[File:Sm_sys_sum_up_2_final.jpg|1200px|SM SYS SUMM 2 display of the Space Shuttle]]

The second SM systems summary display duplicates much of the APU and hydraulics display information, but contains in addition monitors for the on-board stores of hydrogen and oxygen used in the fuel cells (and to replenish the water supplies) and readout of avionics bay temperatures and the operation of the freon cooling loop.

=== APU/HYD (DISP 86) ===

[[File:Spec_86_hyd_apu_final.jpg|1200px|APU/HYD display of the Space Shuttle]]

On this display, a summary of various pressure and temperature readings of the APU and hydraulics systems can be accessed. All parameters are meaningful and represent the internal state of the simulation and possible failure modes.

=== HYD THERMAL (DISP 87) ===

[[File:Spec_87_hyd_thermal.jpg|800px|HYD THERMAL display of the Space Shuttle avionics]]

The hydraulic thermal properties display is used to monitor the status of the hydraulic system in orbit. It shows the basic pressures of the accumulators and the circulation pumps, as well as line temperatures for the various systems driven by the hydraulics. This allows to monitor the proper functioning of the circulation pumps to keep the lines from freezing in cold spots. In addition, the lower left part shows tire pressures for the gear.

This may come as a surprise, but all pressure and temperature readings of the display are real, i.e. reflect the actual simulated thermal state of the hydraulics system.

=== PRPLT THERMAL (DISP 89) ===

[[File:Spec_89_prplt_thermal_final.jpg|1200px|PRPLT THERM display of the Space Shuttle avionics]]

The thermal properties of the propellant feedlines for RCS and OMS thrusters can be monitored on DISP 89. It shows various temperature sensor readings distributed across the aft OMS pods and the forward RCS system. The heating elements are supposed to maintain temperatures between 55 and 75 F in the feedlines, temperature readings outside this range indicate a problem and potentially a frozen feedline. The fuel injector temperature is special in that it measures the temperature of the fuel after it has been circulated through the engine nozzle for cooling, hence it reflects the efficiency of OMS engine cooling. During engine operations, it increases and should be around 220 F.

In FG, the temperature readings are all meaningful represent the action of the heating element simulation in combination with the ambient temperature simulation.

=== PDRS CONTROL (SPEC 94) ===

[[File:Spec_94_pdrs_control_final.jpg|1200px|PDRS control display of the Space Shuttle]]

Using the PDRS (payload deployment and retrieval system) control utility page, various readings of the RMS arm state can be monitored as well as automatic modes configured.

Most important is the central part of the display where a target position and attitude for the end effector can be entered, and in the operator commanded auto mode, the RMS arm can then be moved to the entered target.

In the lower portion of the screen, ready for latch indicators and the MPM status indicators are displayed.

=== PDRS OVERRIDE (SPEC 95) ===

[[File:Spec_95_pdrs_override_final.jpg|1200px|PDRS OVERRIDE display of the Space Shuttle]]

The PDRS override special function page provides the ability to operate the RMS arm via software commands in case the hardware of one or more control switches fails. By selecting the override and then the corresponding item, all hardware inputs to the controller are ignored and replaced by software settings.

In FG, all items which are supported in the RMS operation dialog are also available as software switches, but not all RMS drive modes are supported, and these can also not be selected.

=== PL RETENTION (DISP 97) ===

[[File:Spec_97_pl_retention.jpg|600px|PL RET display (DISP 97) of the Space Shuttle]]

The payload retention display is used to monitor the status of the payload retention system latch microswitches. It indicates the current latch status as well as whether a payload is in the correct position to be latched.

Currently only the payload position 1 is functional, the others are not yet implemented in FG.

=== PDRS STATUS (DISP 169) ===

[[File:Spec_169_pdrs_status_final.jpg|1200px|PDRS STATUS display (DISP 169) of the Space Shuttle]]

The PDRS STATUS display is an SM display available in SM OPS 2 which provides data on point of resolution commanded and actual rates, position and attitudes of the different elements of the RMS arm.

It is a software duplication of the hardware RMS panel at the back of the Space Shuttle cockpit.

=== THERMAL (OPS 0001) ===

[[File:Bfs_thermal_0_final.jpg|1200px|THERMAL BFS display (OPS 0001 SM) of the Space Shuttle]]

The THERMAL display is a BFS display only which provides the crew data on the hydraulic system, heater status, Freon/water loop parameters, tire pressure status, and brake pressure readings.

It is particularly useful to follow in OPS 1 and 3 the Freon loop temperature and the OMS pods thermal state ( for OMS 2 burn )

Space Shuttle

2024-11-21T18:05:38Z

Gingin: /* TAEM/Approach guidance algorithm */

{{:{{PAGENAME}}/info}}
{{hatnote|See also [[Space Shuttle (FG Space Program)]] for the other Space Shuttle.}}
[[File:Spacetripready.png]][[File:Checklistready.png]]

{{Space Shuttle navigation}}

The NASA '''Space Shuttle''' was the world's first operational space plane capable of reaching orbit. It was operated from 1981 to 2011 on a total of 135 missions during which two orbiters, Challenger and Columbia, were lost in accidents.

The Shuttle launch system components include the Orbiter Vehicle (OV), a pair of solid rocket boosters (SRBs) and the external tank (ET) containing the liquid hydrogen and oxygen fuel for the engines of the orbiter. Of these, only the external tank is expendable; the SRBs splash into the sea shortly after launch and are recovered, and the orbiter itself returns to a landing site where it lands like an airplane.

The mixture of a rocket-like launch, a spacecraft-like near ballistic early atmospheric phase and an airplane like approach and landing makes the Space Shuttle a truly unique flying experience.

== Project Aim ==

The aim of the Shuttle Project is to create a highly realistic simulation of the capabilities of the Space Shuttle in FlightGear. While most of the time the real Shuttle is under the control of automatic guidance systems, there are fallback modes to control the spacecraft manually, the so-called CSS (control stick steering) modes, and it is these modes we primarily try to implement.

In addition to the real avionics and control modes, the idea is also to provide various 'educational' modes and instruments in order to explore and appreciate certain aspects of a Shuttle mission more.

The [http://ntrs.nasa.gov NASA technical reports server] supplies a large base of wind tunnel and in-situ performance data of both the mated launch vehicle and the orbiter, and the aerodynamics of the simulated shuttle is based on these documents. The authoritative source for procedures for trajectory management, instrumentation, limits and emergency procedures is the [https://web.archive.org/web/20200602210929/https://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf Space Shuttle Crew Operations Manual] and currently a normal mission, i.e. ascent, orbital insertion, de-orbit, entry, terminal area energy management and landing can be flown largely 'by the book', i.e. following the real procedure for CSS.

In the following, descriptions refer to the development version - the last stable or the release version may not have all features described.

=== Limit and failure modeling ===

The project contains code to simulate the various structural and aerodynamical limits as well as component failures based on sections 4 and 6 of the Space Shuttle crew manual.

The general philosophy on limit modeling is that they can be treated dependent on a user setting as 'soft', 'hard' and 'realistic'. Where applicable, warnings when the state of the orbiter is getting dangerously close to a limit are called out in addition to a recommendation how to deal with the situation. Dependent on the trajectory of the orbiter, there may or may not be sufficient time to redeem the situation.

; soft
: Limit violations are called out, but their violation has no consequences for aerodynamics or component failures.

; hard
: Any limit violation immediately ends the simulation.

; realistic
: In reality, components do not necessarily fail immediately if used outside their design specs. This option applies a probabilistic failure model in which the chance for a component to fail grows with the degree of limit violation. The failure may or may not be immediately visible, e.g. too much qbar upon ascent may damage the heat shield, but this may not be apparent (unless specifically checked) until the heat shield fails upon atmospheric entry.

Component failure is modeled gradually where applicable - while a tire can only blow or not blow, an airfoil or a thruster for instance may lose a certain percentage of its efficiency.

In addition to failures induced by limit violations, the simulation also supports failure scenarios designed to model typical failure modes which could be expected to occur during operations, such as for instance engine failures or lock-up on ascent, coolant loop failures or leaks or similar. Rather complex chains of failures are modeled, for instance a failure of a coolant water spray boiler will lead to subsequent overheating of an APU unit - if this is not realized and proper action taken, the APU will fail subsequently, causing in turn a failure of one hydraulic system which potentially causes downstream failures of airfoil actuators or main engine gimbal capability.

== The mated launch vehicle ==

At liftoff, thrust for the shuttle is provided by its three main engines (SSMEs) and the two SRBs. The assembled launch configuration has a height of 184.2 ft (56.1 m) and a mass of about 4,470,000 lb or 2.030 tons (in addition to payload), over 90% of this being propellant. The main engines would at this point be incapable of lifting the launch stack.

The SRBs burn an ammonium perchlorate composite fuel with a relatively low ISP of 268 s in vacuum, supplying 2,800,000 lbf of liftoff thrust each, this is supplemented by the SSME burning liquid hydrogen/oxygen with an ISP of 455 s, supplying an additional total liftoff thrust of 1,180,000 lbf. At liftoff, the shuttle hence reaches a thrust/weight ratio over 1.6, i.e. it leaves the launch pad rapidly.

Control during ascent is provided by thrust vectoring of both the SRB and SSME nozzles. The real-world CSS scheme is a 'stick controls rates' scheme which for stick to neutral does 'attitude hold' which makes it possible to control the launch trajectory very precisely.

=== The Solid Rocket Boosters ===

Each SRB weighs about 1,300,000 lb, out of which 1,100,000 is propellant weight. The propellant of the SRBs is shaped to provide a high liftoff thrust, followed by a thrust reduction during the phase of the highest dynamical pressure (max. qbar). The actual thrust as a function of time is fairly complicated:

[[File:SRB thrust.png|400px|thumb|none|Thrust characteristics of the Space Shuttle Solid Rocket Boosters]]

The distribution is faithfully modeled in FG and the definitions to match the real thrust characteristics is taken from the [http://jsbsim.sourceforge.net/download.html JSBSim code repository]

The SRBs can not be throttled, once ignited, they provide thrust as explained above. SRB ignition takes place some three seconds after main engine ignition, and once they ramp up to full thrust, the shuttle has no choice but to leave the launch pad. For thrust vectoring, SRB nozzles can be gimbaled up to 8 deg in both pitch and yaw axes, a roll moment is created by gimbaling the two SRBs in opposite directions.

[[File:SRB 2.jpg|800px|thumbnail|none|Early ascent on combined SRB and SSME thrust]]
[[File:Sonic boom.webp|800px|thumbnail|none|Sonic boom and max dynamical pressure]]

As of May 2015, SRB separation happens automatically once the thrust drops below some threshold to avoid having to drag dead weight, but there is no provision to manually separate. The SRBs are pushed away from the remaining launch vehicle by separation motor burns. These (including the separation animation with still burning SRBs) are modeled in FG, however due to technical issues with the submodel code at high velocities, thrust of the separation motors in the sim is set larger than in reality to provide the same visual separation dynamics.

The SRBs are implemented as ballistic submodels, i.e. they follow a correct trajectory and ascent with the shuttle, however since (unlike the shuttle) they are not accelerating, they visually fall behind quite quickly.

=== The Main Engines ===

The three main engines (SSMEs) are used during ascent and burn propellant from the ET. They are mounted in a triangular configuration at the stern, tilted by 13 degrees with respect to the spacecraft main axis and can be gimbaled by 10.5 degrees in the pitch and by 8.5 degrees in the yaw axis. The reason for the tilted arrangement is to have a sensible CoG of the OV together with the ET during the later ascent stages. The heavy oxygen is stored forward in the ET, leading to a fairly forward CoG for the mated vehicle such that the SSMEs can be vectored through the CoG. This assembly is faithfully modeled in FG.

[[File:SSME.jpg|800px|thumbnail|none|Late ascent phase on SSME thrust]]

The engines can be throttled between 67 and 109% of rated power, this is necessary to keep the launch vehicle within structural limits during the high qbar phase in the atmosphere and later close to MECO as the propellant in the ET is almost depleted. Thrust increases during ascent as the exhaust gases do no longer have to push against an atmosphere. Both liftoff and vacuum thrust of the modeled engines are in agreement with published values.

Since the SSME's are mounted much closer to each other than the SRBs, the Shuttle loses significant yaw and roll maneuverability after SRB separation. However as the spacecraft is nearly out of the atmosphere by then, no such maneuverability reserves are actually needed.

In FG, the throttle controls all three SSMEs during ascent. Engines ignite once throttle is moved above 67%, this triggers the SRB ignition. If the throttle is moved below 67%, the engines will stop, however they will restart once throttle is moved again up as long as fuel is available in the ET.

The engine numbering by NASA has the center engine as number 1, the left engine as number 2 and the right engine as number 3 and these numbers are used in in-sim callouts of engine failures. For some failure modes, engines will not respond to throttle any more, in this case the cutoff switches have to be used. These are {{Key press|Control|q}} for engine 1, {{Key press|Control|w}} for engine 2 and {{Key press|Control|e}} for engine 3. An engine that has been shut down by the cutoff switch will not re-ignite.

The propellant for the SSMEs is carried in the ET. The tank has a liftoff weight of approximately 1,680,000 lb (760 tons) and a dry weight of about 66,000 lb (dependent on version - the Space Shuttle menu offers an option to fly older and heavier tanks). The ET is the only expendable component of the launch stack, it is dropped after MECO upon almost reaching orbit and then the shuttle uses the OMS to attain orbit while the tank re-enters the atmosphere half an orbit later and breaks up during entry.

[[File:Et_sep.jpg|800px|thumbnail|none|External tank separation]]

In FG, the tank is normally separated using {{Key press|d}}. This is vetoed if the Shuttle has unsafe yaw, pitch or roll motion in which case the RCS should be used to stabilize the orbiter before ET separation. If an emergency separation needs to be performed, {{Key press|Control|d}} overrides the veto. At separation, a translational RCS burn will automatically push the shuttle away from the tank.

After separation, the ET will approximately co-orbit with the OV, i.e. unless the Shuttle ignites the OMS engines, the tank will be visible for a long time, slowly drifting off, and it is quite possible to use the Shuttle's RCS engines to do a visual inspection of the tank.

[[File:ET_sep_2.jpg|800px|thumbnail|none|The ET seen from the Shuttle]]

=== A note on aerodynamics of the mated vehicle ===

With the ET and SRBs attached, the launch stack has quite different aerodynamical characteristics than the OV alone, for instance the stack is more yaw-stable than the orbiter and its pitching moment as function of alpha and rolling moment as function of beta are very different. Where such data could be obtained from wind tunnel tests with the mated stack, it has been used in the simulation.

As in reality, the simulated shuttle has an automated downward elevon deflection schedule with Mach number upon ascent to provide further load relief for the wings (with corresponding aerodynamical forces acting).

In general though, aerodynamical effects are subleading, the ascent dynamics is dominated by the thruster forces and the flight control systems have a large margin to compensate for them.

=== The Ascent Performances ===

Space Shuttle Main Engine thrust, [https://en.wikipedia.org/wiki/Specific_impulse ISP], and consumption is now within a percent of the real datas (Dev version of December 2020)
The mixture ratio in real was around 6, and it is what we observe in the sim (6 times more liquid Oxygen burnt than liquid Hydrogen). Hence, Main Engine Cut Off (MECO) time is matching real one. Plus, the propellant remaining at MECO, called the Final Performance Reserve (FPR) is now within a percent (15000 pounds). It makes launch with high payload into a high inclination Orbit (towards ISS typically) really interesting and limitating performance wise, like in real.

An interesting read about that FPR, written by a former Shuttle Flight Controller: [https://waynehale.wordpress.com/2014/10/08/understanding-sts-93-the-key-is-mixture-ratio/ Wayne Hale: The key is Mixture Ratio]

You can find below some in sim datas compared to real one coming from the Shuttle Crew Operations Manual (SCOM).

[[File:Stage_1_in_sim.png|600px|thumbnail|none|Stage 1 Velocity Vs Time in Sim]][[File:Stage_1_scom.jpg|600px|thumbnail|none|Stage 1 Velocity Vs Time in real]]
[[File:Stage_2_in_sim.png|600px|thumbnail|none|Stage 2 Velocity Vs Time in Sim]][[File:Stage_2_scom.jpg|600px|thumbnail|none|Stage 2 Velocity Vs Time in real]]

=== CSS DAP schemes for ascent ===

During ascent, the stick controls thrust vectoring for both SSMEs and SRBs. The following two DAP schemes are available:

; Thrust vectoring
: This is the real CSS ascent mode for the shuttle in which stick motion controls rate, stick to neutral commands an attitude hold. Internally a PID controller vectors the thrusters and uses the stick input as a bias for the error. This is a very stable scheme and can be easily used to achieve high precision in controlling ascent speed or orbital inclination.

; Thrust vectoring (gimbal)
: This is an educational scheme in which the stick motion directly controls the engine gimbal, i.e. the pilot needs to do the task of the PID controller himself. To make things somewhat easier, the engines are automatically vectored through the stack's CoG, i.e. outside the atmosphere stick neutral corresponds to zero moments acting on the stack. In the atmosphere, the control input hence needs to compensate for aerodynamical forces. Launch in this scheme is fairly rough and it is not possible to reach high precision, but it is possible to fly into orbit and gain a first-hand experience of the forces acting on the stack.

{{Key press|m}} switches between the ascent DAPs. {{Key press|Control|m}} switches from the ascent to the orbital DAP modes (do not use an orbital DAP for ascent control unless you know very well what you're doing).

=== Ascent structural and aerodynamical limits ===

The following structural and aerodynamical limits need to be observed during ascent:

* Dynamical pressure qbar < 819 lb/sqf (modeled)

This is a structural limit for the orbiter and mated stack, in actual operations the orbiter should be kept below 650 lb/sqf.

* Wing bending moment coefficient CBW between -0.019 and 0.019 at max. qbar (modeled)

At max qbar, the wing bending moment is a function of Mach number and AoA. Since Mach number is close to 1.4 in this phase of the flight, this limit basically translates into alpha between -8 degrees and 2 degrees. This can only be achieved if the orbiter is in inverted flight.

* Translational accelerations Nx between 0 and 3.11 g (modeled), Ny between -0.18 and 0.18 g (not modeled) and Nz between -0.06 and 0.73 g (not modeled).

These are structural limits of the mated stack to acceleration rather than aerodynamical forces. Especially the Nx (acceleration along the orbiter axis, i.e. main engine thrust) is important and requires to throttle down the SSMEs towards the end of the burn time.

* Late ascent trajectory may not drop below 265.000 ft (modeled)

This is a heat load limit for the external tank insulation, if the thermal protection of the ET fails, it will explode.

== The Shuttle in orbit ==

For maneuvering in orbit, the OV is equipped with three RCS thruster clusters and the two OMS engines. The propellant for these systems is monomethylhydrazine (MMH) oxydized with dinitrogen tetroxide, resulting in a specific impulse of 312 s. This is an hypergolic fuel combination (i.e. ignites automatically). OMS and RCS tanks have an interconnect valve, however only the RCS can be fired from the OMS propellant reserves, not vice versa (currently not modeled).

The OMS engines are located at the rear of the spacecraft in pods attached to the fuselage. Two of the RCS clusters are attached to the OMS pods, one is located at the spacecraft nose.

=== The Orbital Maneuvering System engines ===

The two OMS engines provide a thrust of 6,000 lb and, using the propellant reserves of 7,773 lb of nitrogen tetrozide and 4,718 lb of MMH can induce a total velocity change of about 1000 ft/sec if all propellant is spent. Typically half of this is used to push the OV into a proper orbit after ET separation and for the de-orbit burn, the rest is available for orbital maneuvers such as inclination adjustments.

Once in orbit, in FG throttle control is transferred to both OMS engines. They can be throttled from zero to 100% of nominal thrust and are automatically vectored by the flight controls through the CoG of the orbiter. The real shuttle has a DAP for thrust vectoring of the OMS engines as well as the option of using a single engine with partial thrust vectoring, only the first option is currently modeled.

[[File:OMS_burn.jpg|800px|thumbnail|none|OMS burn for orbital insertion]]
[[File:MS cockpit view Orbit.webp|800px|thumbnail|none|Orbit cockpit configuration]]

=== OMS DAP schemes ===

In orbit, the throttle controls OMS engine thrust. The following DAP schemes are available:

; OMS TVC
: This is a stick-controls-rates scheme which utilizes thrust vectoring for the OMS engines. It resembles in principle the ascent thrust vectoring, except for the fact that the OMS engines are far less powerful and hence rates and the transition to the set rate are a lot slower. Note that this DAP will only control the Shuttle if the OMS is firing.

If TVC for the OMS is not feasible (for instance because the OMS engine gimbal actuators are damaged), the OMS engines can also be fired with an RCS attitude-holding rotational DAP active (for example '''RCS DAP-A'''. In this case, attitude control is provided by the RCS thrusters and thrust by the OMS engines.

=== The Reaction Control System ===

The RCS system consists of three modules, one forward at the nose and two at the OMS pods. The forward module contains 14 primary and 2 secondary thrusters, each aft module carries 12 primary and two secondary thrusters. Propellant reserves in each module are 1,477 lb of oxidizer and 928 lb of MMH. Each primary thruster has 870 lb of thrust with an ISP of 289 s, the secondary Vernier thrusters produce a mere 24 lb each with an ISP of 228 s. Due to geometric constraints, the thrusters are not aligned with the main spacecraft axes or in the same plane (for instance, there is no purely downward firing nose thruster, as its nozzle would have to fire through the heat shield). The layout of the whole system is shown below:

[[File:RCS Jet IDs.gif|600px|Space Shuttle RCS layout]]

Not all thrusters point orthogonal, and not all thrusters have the same nominal thrust - the complete list is as follows

[[File:RCS Break Down Table.gif|600px|List of Space Shuttle RCS thrusters and orientation]]

All of these thrusters are faithfully modeled in FG with their actual orientation and nominal thrust values, including the system of Vernier thrusters, equipping the Space Shuttle with a grand total of 51 distinct engines.

=== RCS DAP schemes ===

The real Space Shuttle has a multitude of (partially mission-specific) DAP schemes, each with different gains and deadbands, which control the thruster firing pattern in response to the controllers. A fair selection of these is implemented in FG. In the real Shuttle cockpit, there is both a rotational hand controller (RHC) and a translational hand controller (THC) to initiate either rotations of the shuttle or translational accelerations (e.g. for approach and docking). In FG, {{Key press|m}} corresponds to switching from THC to RHC to OMS control and back, {{Key press|Shift|m}} switches between the different DAPs and {{Key press|Control|m}} is the override switch to aerodynamical controls. The HUD will display the currently selected mode for clarity.

Due to the geometry of the thruster arrangement, there is significant mode mixing. For instance, a lateral translation firing nose and right pod thruster with the same thrust would also induce a yaw motion (since the modules do not have the same distance to the CoG) and a roll (since they are not in the CoG plane and in fact not even in the same plane). In most implemented modes, the FCS logic takes care of most of these effects by firing additional thruster to cancel the unwanted motion, however in some modes this is not easily possible and mode mixing has to be anticipated and accounted for manually. This is in fact the same as in the real Shuttle.

The Shuttle has four different control pushbuttons (implemented in the menu) to control the basic way the orbital DAP works. These are AUTO, INRTL, LVLH and FREE.

If AUTO is selected, the RCS is controlled by the on-board flight software (specifically either the pointing and tracking routines available on the UNIV PTG display or the automatic burn attitude maneuvering routines available on the MNVR display). In this mode, stick control input is not used. Note that if an automatic maneuver program is selected, the controls need to be switched to AUTO prior to the start of the program. If this is not done, a SEL AUTO warning message is created.

In INRTL (inertial), the stick controls roll rates and the Shuttle holds inertial altitude for stick to neutral. The orbiting Shuttle in this mode thus has an apparent slow attitude drift with respect to the horizon.

In contrast, LVLH (local vertical, local horizon) commands an attitude hold with respect to the local horizon, i.e. the Shuttle appears not to change attitude relative to Earth. Again in this scheme, the stick controls rates.

The following DAPs are available for INRTL and LVLH:

; RCS DAP-A
: A precision 'stick controls rate' scheme in which stick to neutral commands an attitude hold. The mode has fairly strict deadbands and steep gains and hence uses comparatively much propellant to stabilize attitude.

; RCS DAP-B
: As DAP-A, but more permissive in terms of deadbands, trades less strictly stabilized attitude against reduced propellant consumption.

; RCS DAP-A VERNIER
: A 'stick controls rate' scheme in which the Vernier thrusters are used to maneuver the Shuttle. The Verniers are not very powerful and moreover fire in an awkward geometry, so there is significant mode mixing into translations when using them and the response of the Shuttle is very slow - the mode should mainly be used for automatic attitude hold as it is very propellant-friendly.

; RCS TRANS ATT HLD
: A translational DAP in which 'attitude hold' is commanded for all rotation channels. This makes this mode very stable and controllable at the expense of an increased propellant consumption - use e.g. for a precision approach to a docking.

; RCS TRANS LOW-Z ATT HLD
: No upward-firing thrusters are used in this mode to avoid plume impingement on a satellite or docking target. For this reason, forward and backward firing jets are used simultaneously which are both angled slightly upward. For -Z-translations, this causes a 12 times higher fuel consumption. For weak thrust attitude control works well, for strong thrust the controller is, without using upward-pointing thrusters, unable to completely control the pitching motion.

Finally, FREE puts the orbiter into free drift. Stick to neutral then commands all RCS jets off, and stick movements control angular acceleration. The following DAPs are available for this control:

; RCS rotation
: This is a simple scheme in which the stick motion controls thrust, i.e. angular acceleration. Stick to neutral commands no thrust, i.e. the Shuttle will continue its current rotation.

; RCS ROT TAIL ONLY
: A 'stick controls thrust' scheme in which the nose module is not used. This causes significant mode mixing.

; RCS ROT NOSE ONLY
: A 'stick controls thrust' scheme in which the OMS pod modules are not used. This causes significant mode mixing and has very limited roll control (the roll moment only comes from the position difference between left-mounted and right-mounted upward and downward firing thrusters)

; RCS translation
: A translational DAP in which the stick controls translational thrust along the spacecraft x, y and z axes. Stick to idle commands no thrust, but the Shuttle will of course retain its relative velocity to a fix point until counter-thrust is used. RCS translation can be used for emergency de-orbit burns if the OMS is not available. Limited compensation is done for cross-coupling to rotational modes.

; RCS TRANS LOW-Z
: To prevent thruster plume impingement on a docking target, say the ISS, in this mode all upward-firing thrusters are inhibited. To provide the deceleration force for a docking (which is needed in -Z direction), foreward and backward firing thrusters are used simultaneously - since they point about 10 degrees upward, this provides a downward acceleration without upward plume at the expense of 12 times higher than normal propellant consumption. There is strong cross-coupling to a pitching motion.

The following DAPs are available for re-entry (OPS 304):

; RCS ROT ENTRY
: A 'stick controls rates' DAP designed for entering the atmosphere which enforces a 'no sideslip' attitude in which the nose module is not used. This has very strict deadbands and aggressive gains to combat the yaw instability of the Shuttle upon entry, significant mode mixing and is very propellant-consuming. Do not use in orbit and only activate at the entry interface once the shuttle has the correct attitude! During entry, the DAP will gradually transfer control to the 'Aerodynamical' DAP - at qbar of 10 lb/sqft the roll axis, at 40 lb/sqft the pitch axis and at around Mach 3.5 the yaw axis.

; Aerojet
: The Aerojet DAP is close to the real entry DAP used by the Shuttle. Its RCS part works similar to RCS ROT ENTRY, but control is not transferred to to the Aerodynamical DAP but to the atmosphere part of Aerojet (see below) which employs the same rate control routines as the RCS part. The scheme also supports an automatic AoA control scheme in which the pilot only has to manage the roll axis during entry, which makes this the most easy to fly DAP for entry and atmospheric flight.

For precision control, the keyboard is a more suitable input device than a joystick or a mouse since exact nulling of rates is somewhat easier with keystrokes.

==== Orbital DAP configuration ====

As of November 2015, the Shuttle's orbital DAPs are configurable using the SPEC 20 utility. This allows to set characteristics such as the roll rates achieved for a given controller movement, deadbands for attitude and rate holding as well as to switch the nose / aft RCS pods selectively off to conserve propellant.

[[File:Dap_config_spec_20.jpg|600px|thumb|none|DAP utility display of the Space Shuttle]]

Note that the DAP characteristics configuration allows to specify unstable or ineffective use of the RCS, thus changes should be entered with care.

==== Key mapping for RCS rotation DAP ====

{| class="keytable"
! Key
! Function
|-
|{{Key press|4}}
|Roll left
|-
|{{Key press|6}}
|Roll right
|-
|{{Key press|2}}
|Pitch up
|-
|{{Key press|8}}
|Pitch down
|-
|{{Key press|[}}
|Yaw left
|-
|{{Key press|]}}
|Yaw right
|-
|{{Key press|5}}
|Cut thrust
|}

==== Key mapping for RCS translation DAP ====

{| class="keytable"
! Key
! Function
|-
|{{Key press|4}}
|Left
|-
|{{Key press|6}}
|Right
|-
|{{Key press|2}}
|Down
|-
|{{Key press|8}}
|Up
|-
|{{Key press|[}}
|Backward
|-
|{{Key press|]}}
|Forward
|-
|{{Key press|5}}
|Cut thrust
|}
.

=== Spacewalk ===

The Shuttle version as of May 2015 contains a 'proof of concept' spacewalk view designated 'EVA'. This is intended to simulate the view of an astronaut using a MMU. In the EVA view, use {{Key press|Shift|E}} to initiate spacewalk. The stick then controls the MMU thrusters and {{Key press|m}} is used to switch between the translational and rotational modes of the MMU.

Before spacewalk is initiated, the yaw, pitch and roll rates of the Shuttle need to be nulled (since control inputs during spacewalk refer to the MMU, the Shuttle also can't be controlled from this view).

Once outside, the MMU can be used to float around the Shuttle, or to inspect co-orbiting objects. However, note that it is impossible to leave the EVA view unless the astronaut maneuvers back to the airlock. Currently it is not possible to see spacewalk from outside, nor can the view direction be adjusted - in a future implementation, spacewalk will be improved using the FG walker functionality.

== Aerodynamics of the Space Shuttle Orbiter ==

The conditions encountered by the Space Shuttle span a wide range from a thin, rarefied atmosphere at Mach 27 to a sea level atmosphere flown at about Mach 0.6. Over this range of conditions, the handling characteristics change quite dramatically.

Somewhat simplified, one can divide the atmospheric entry in three phases - an initial near-ballistic entry phase in which airfoils are essentially useless, an aerodynamical entry phase in which the Shuttle is controlled by airfoils and aerodynamical forces are very noticeable on the trajectory, but in which the flight dynamics is completely different from that of an airplane and the final approach and landing phase during which the Shuttle is flown like an aircraft.

[[File:Shuttle-landing04.jpg|800px|thumbnail|none|Early near-ballistic entry phase]] 
 
[[File:Glowing red 2.jpg|800px]]

During these phases, control is passed from RCS jets to the airfoils - the inboard and outboard elevons at the trailing wing edges and the rudder/speedbrake at the tail stabilizer fin. The elevons can be deflected from -40 to 25 degrees, the rudder from -25 to +25 degrees. At a qbar of 10 lb/sqf roll control is taken over by the airfoils, at 40 lb/sqf pitch control is managed by airfoils and below Mach 3.5 finally yaw control is transferred, at which point the airplane-like phase of the entry starts. In addition to the primary airfoils, the Shuttle is equipped with a body flap which can be used to adjust trim.

During the first two phases, the Shuttle is flown with a high AoA (initially 40 degrees) to create a detatched bow shockwave which keeps the heat of atmospheric entry away from the fuselage. The characteristic hallmark of this attitude is that the stabilizer fin is shadowed by the wings - this renders the rudder ineffective above Mach 6 and makes the Shuttle yaw unstable against sideslip above Mach 2, i.e. any sideslip must be very accurately controlled by the FCS during entry or the Shuttle will tumble uncontrolled. This can not be done by the rudder, thus yaw jets remain crucial for controlling the Shuttle down to Mach 3.5.

Another effect is that the elevons deflected upward are in the lee of the wings, significantly reducing their effectivity as compared to downward deflections. However, in the entry regime, operating the elevons upward is more advantageous due to heating constraints.

=== Lift / Drag ===

Despite being designed for a gliding approach and landing, the Shuttle is not actually a very good glider - even close to approach, the glide ratio (i.e. L/D) reaches about 4.5, much less than most normal planes would have.

[[File:L-D-mach.gif|‎500px|thumbnail|none|Lift to drag as a function of AoA for different Mach numbers]]

The maximum of L/D varies somewhat with Mach number, however for hypersonic flight thermal constraints force a high AoA and aerodynamical efficiency is a secondary concern. Only in the supersonic to subsonic phase is the Shuttle flown close to its optimum glide ratio.

Due to the Delta-wing design, L/D has no pronounced stall even at high AoA in any region. However, the need to have sufficient lift despite the relatively poor aerodynamics forces a high touchdown speed of about 200 kt.

=== Longitudinal Dynamics ===

In the near-ballistic entry phase, pitch is controlled by an attitude-hold mode of the RCS, however elevons are automatically trimmed by the FCS to negative (upward) deflections to take some of the load early on to conserve propellant.

The pitching moment induced by the control surface varies dramatically as function of Mach number.

[[File:Control response.gif|500px|thumbnail|none|Pitching CM moment]]

As seen from the figure, at high Mach numbers the response is fairly flat (i.e. large elevon deflections are needed to control the Shuttle) and also non-linear (upward deflections cause much less pitching moment than downward deflection). In contrast, at low Mach numbers small elevon deflections already cause large moments and the response is almost linear. In all regimes, the pitching moment is normal force (i.e. AoA) dependent.

Since the elevons supply both pitching and roll control, at high hypersonic Mach numbers roll controls are close to being saturated with elevons deflected near full up. To open up better roll control, below Mach 10 the speedbrake is opened to provide a pitching moment relieving the elevons, and the Shuttle's body flap can also be trimmed upward.

=== Lateral stability ===

As mentioned above, during most of the entry phase, the Space Shuttle has no rudder action and the yawing moment as a function of sideslip angle beta is negative, indicating instability. This means that the FCS has to manage yaw stability by commanding yaw thrusters to maintain near zero beta, which is increasingly more challenging as the Shuttle penetrates deeper into the atmosphere and aerodynamical forces grow while thrust is reduced as compared to nominal vacuum values. This implies that a sizable amount of RCS propellant (about 1/3 of the capacity to be on the safe side) needs to be available before atmospheric entry.

Below approximately Mach 6, the rudder starts to contribute to yaw stability and from Mach 3.5 down to Mach 2 where the yawing moment finally becomes positive only the rudder is used. The roll behavior of the orbiter before any FCS is somewhat skittish as the roll moment as a function of roll rate is not a large damping term over most of the Mach range. The FCS of the Shuttle in FG therefore does not place yaw and roll axis directly under pilot control. The rudder is always commanded to minimize beta and no pilot input for the rudder should be needed or used unless sideslip is explicitly desired. The elevons are commanded to provide a simple roll damper to make control smoother.

The real Shuttle has in addition a '''NO Y JET''' mode to stabilize the orbiter during entry in which the elevons are used to control yaw. This leads to significantly reduced roll control since roll then needs to be driven by adverse yaw till the rudder picks up sufficient airflow. This mode has been implemented since dev version of july 2017.

=== A note on thruster efficiency in the atmosphere ===

Thrusters used in the hypersonic rarefied airflow of the upper atmosphere do not only cause the yaw, pitch and roll moment by the thrust acting at a certain distance to the CoG, but also are subject to plume impingement on the orbiter fuselage and interactions with the air flow field.

While impingement generically degrades the effectivity, the interaction moment can somewhat counter-intuitively act both directions. In particular the yaw moment is increased by the airflow, helping to stabilize the Shuttle.

As of May 2015, none of these effects is modeled in Flightgear.

=== Control cross couplings ===

The Shuttle has significant cross couplings between the elevon deflection in pitch and roll mode and the rudder as a function of Mach number, all of which are faithfully modeled in FG. One of the main effects is that upward elevon deflection alters the airflow at the aft fuselage, creating additional suction effects which alter aerodynamical forces.

In particular, at supersonic speeds yaw stability is somewhat improved at high upward elevon deflection while the effect reverses at subsonic speeds. At the same time, roll control is significantly reduced at full elevon deflection, with the effect being more pronounced at low than at high Mach numbers.

Control surface effectiveness in general drops with increasing Mach number, however the speed at which this happens is different for elevons and rudder.

=== Aerodynamical DAP schemes ===

There are two different control schemes available for the aerodynamical part of the Shuttle's flight - one of them based on the real Shuttle DAP, the other educational.

; Aerojet
: The Aerojet DAP is closest to what the real Shuttle uses. It is a scheme in which the stick commands pitch and roll rates and stick in neutral position commands attitude hold. Above Mach 3.5, in addition an automatic pitch control mode can be activated which maintains the scheduled safe entry AoA. Flying the Shuttle is very easy in this mode - there is no operational need to use trim or rudder and response to control input is crisp and precise. During entry, Aerojet can manage even agressive roll reversals inside the stable region.

; Aerodynamical
: This is an educational mode in which the Shuttle is flown similar to an airplane, i.e. the stick basically controls the airfoil positions, and in order to achieve level flight with stick neutral, trim has to be used. Since the Shuttle is yaw-unstable at high Mach numbers, this mode still has automatic stability augmentation, i.e. rudder and ailerons are commanded automatically to minimize sideslip. Entry can be flown with this mode starting in-orbit with '''RCS ROT ENTRY''' and illustrates the amount of work the rate controller has to do as well as gives a hands-on feeling for hypersonic aerodynamics. This however is somewhat challenging and it is possible to maneuver the Shuttle outside its stability envelope using too agressive maneuvers. Once below Mach 5, the Shuttle responds well and stable to direct aerodynamical control.

=== Entry and touchdown structural and aerodynamical limits ===

The following structural and aerodynamical limits need to be observed during entry and landing:

* Dynamical pressure qbar < 375 lb/sqf (modeled)

This is a structural limit for the orbiter and the airfoils, beyond this the actuators can no longer move the airfoils, leading to a loss of control. In nominal operations the orbiter should be kept below 250 lb/sqf.

* Peak temperature < 2900 F (modeled)

This is the approximate limit beyond which the thermal protection system fails, with subsequent structural failure of the overheated airframe and loss of the orbiter.

* gear extension speed < 312 KEAS (modeled)

Structural limit of the gear against aerodynamical forces.

* vertical speed upon touchdown < 9 ft/sec (modeled)

This is the structural limit of the main gear struts, and their destruction is fully modeled in 'realistic' mode.

* airspeed upon drag chute deployment < 230 kt (modeled)

The drag chute has a safety pin which disconnects the chute if the airspeed is higher than the stability limit. This is fully modeled.

* roll speed of tires < 230 kt (not modeled)

This is the certified maximal speed at which the tires don't blow.

* derotation speed < 2 deg/s (modeled)

This is the structural limit for the nose gear strut, and nose gear breakage is fully modeled.

* AoA < 15 deg on touchdown (modeled)

Beyond this angle, the body flap and tail structure of the orbiter touch the ground before the main gear does.

[[File:Fin.jpg|800px|thumbnail|none|Touchdown and drag chute deployed]]

== Systems ==

Most of the Shuttle's systems are designed around the philosophy that failure of any one component should allow the mission to continue and failure of two components should still allow a safe return to Earth. As a result, most systems exist triple, and the loss of one subsystem is not normally felt when operating the Shuttle, only a loss of two subsystems requires to take special action and compromises the maneuverability of the vehicle.

In the real Shuttle, many system switches have a 'GPC' (general purpose computer) setting in which the computer controls a system automatically and an 'on' setting in which the system is manually controlled. In FG, the system control is a bit simplified as no GPC or mission control is simulated and not all existing sensor readings are simulated which would be necessary for manual control. Often 'GPC' and 'on' are merged into one setting for which, dependent on system, either the user has to always control a system manually or a control routine is activated and no manual control is possible.

=== Electric Power Generation ===

Electricity aboard the Shuttle is generated by three fuel cells (FCs) which produce electricity utilizing the reaction of cryogenic hydrogen and oxygen into water (which is then used in the environment system). Each fuel cell can supply about 12 kW of power, which means plenty of redundancy given the normal power consumption of the orbiter is about 14 kW.

The fuel cells normally circulate hydrogen and oxygen in a closed loop to avoid losses, however they have to be periodically purged (reaction products vented into space) to avoid their effectivity to decrease by contamination.

As of June 2015, the power generation as well as the coarse power balance of the orbiter is modeled (i.e. switching components on which use electricity will have to be supplied by the running FCs), however not all the details of the electrical distribution system or the reactant feed lines are done. In normal operation, the electrical power system should require very little crew intervention.

=== Auxiliary Power Unit and Hydraulics System ===

Thrust vector control of the SSMEs during ascent, movement of the various aerosurfaces, deployment of the landing gear and brakes/nose wheel steering all rely on hydraulic pressure to operate.

The Space Shuttle is equipped with three independent hydraulics systems, each of them powered by an Auxiliary Power Unit (APU), a turbine utilizing hydrazine as propellant. Under normal load conditions, each APU utilized about 3 - 3.5 lb of propellant per minute. With a hydrazine load of 332 lb, this means the system can be operated for about 90 minutes under nominal conditions or be run in a power-saving mode for 110 minutes during an once around abort. This means that the APUs have to be switched off when not used - they are powered down as part of the post-MECO operations and powered up as part of the atmospheric entry preparations.

As compared to the rest of the Shuttle's systems, the APU turbines with with 180 kW power each generate a lot of waste heat which ends up warming the hydraulic fluid and the lube oil. The APUs are operated at a temperature of over 390 K (250 F) though, so for an APU cold start it takes a bit more than 10 minutes to reach that temperature. Afterwards, the water spray boiler systems have to be used to cool hydraulic fluid and lube oil - they are supplied by three water tanks containing 142 lb of water each and can spray up to 10 lb / minute for cooling purpose. Overheating APUs can not be run for more than 2-3 minutes before they fail.

When not in use, electrically powered hydraulic circulation pumps keep the hydraulic fluid moving such as to equalize temperatures in the components.

In case of a hydraulic failure, Priority Rate Limiting (PRL) for the airfoils is used to allocate the remaining power as efficiently as possible. Usually the elevons move with 20 deg/s and the rudder with 14 deg/s, however in the case of multiple hydraulic failures, these numbers are reduced to 13.9 deg/s for elevons and 7 deg/s for the rudder. The orbiter is still fully controllable in this case, but not as responsive to agressive maneuvers.

As of June 2015, the APU and hydraulic system is modeled with a fair amount of detail and operated from a dedicated menu. APUs need to be started as part of the pre-launch checklist - refer to Help/Aircraft Checklists for the detailed procedure. '''If the hydraulic system is not available during ascent, this will result in loss of the vehicle after SRB separation as there is no control over the Shuttle if the SSMEs can not be gimbaled.''' Also PRL for all airfoils is fully supported.

Operation of the water spray boilers is realistically integrated into the heat transfer model of the Shuttle (see below), including the failure of overheating APUs.

=== Active Thermal Control System ===

In orbit, the Shuttle's systems use on average about 14 kW of power, which eventually ends up heating the interior of the pressure vessel. Active cooling systems carry the heat load away and radiate it into space. A water coolant loop system takes care of the avionics bays and the cabin and exchanges heat with a two loop freon coolant system which also cools systems elsewhere in the Shuttle. The freon is circulated through the radiator panels located on the inside of the payload bay doors and dumps a maximum of about 18.000 W of heat into space.

If the payload bay doors are closed (such as during ascent or entry), the freon loop can be cooled by flash evaporators which utilize quickly evaporating water sprayed on the freon tubes as coolant. To provide the cooling performance of the radiator, this system uses about 66 lb of water per hour, i.e. can only be a temporary measure as the water storage aboard would be quickly depleted otherwise.

The heat balance in space is also influenced by the orientation of the Shuttle relative to the Sun and Earth - sunward facing surfaces tend to heat up to 350 K whereas shaded surfaces may cool down to 150 K. To ensure ice-free thruster and other exhausts, electrical heating elements may therefore be needed.

Orbiter heat management often combines cooling systems and attitude - for instance placing the OV into a tail to Sun inertial attitude minimizes incident heat and allows to cool the freon down so that it can act as a heat sink for about 15 minutes even without the radiator deployed, a technique known as 'cold soak'. Similarly, orienting the payload bay towards Earth ensures that even during the night, temperatures don't drop too much so that EVA work is possible. Temperatures can be equalized across the Shuttle by slowly rotating the spacecraft.

As of June 2015, the FG Shuttle includes a fairly sophisticated simulation of the heat balance, including incident heat flux from Sun and Earth dependent on surface normal and albedo, internally generated heat in the avionics bays, heat transport via conduction and via the cooling loops, radiated heat from the surfaces the action of the flash evaporators and the radiator. Most real heat-management techniques, including cold soak and slow rotations, are fully supported.

[[File:Shuttle coldsoak.jpg|600px|thumbnail|none|Cold-soaking the Shuttle's freon loops in preparation for de-orbit.]]

Thermal inertia of the Orbiter is generically high - temperatures adjust at timescales of hours rather than minutes to their equilibrium values. For educational purposes, it is possible to choose simulation options which speed up the approach to thermal equilibrium by a factor or 10 or 100 respectively - this will result in an almost immediate response of the temperature distribution to e.g. changes in attitude. These options should be used with care.

=== Main Propulsion System ===

Under the name Main Propulsion System (MPS), the various subsystems operating the SSMEs are summarized. This includes the SSME controllers (two per engine for redundancy), the propellant feeding system supplying liquid hydrogen and oxygen to the engines and the various hydraulically operated valves, a helium system to supply purge gas flows and emergency hydraulics power and finally the engines themselves.

The SSME's feed high-pressure propellants into the combustion chamber. Power for the turbo pumps is provided by partial pre-combustion of the propellant, and ullage pressure in the external tank is maintained by branching off a small fraction of vaporized propellant back into the tank. The precise opening of the propellant feeding valves which throttles the engines is governed by the controllers which in turn receive throttle commands from the Shuttle's guidance computers.

For the most part, the MPS settings are controlled on the ground prior to launch and not changed during ascent, however after MECO there are about 5,200 lb of propellant trapped in the feeding manifolds which need to be dumped. During this propellant dump, high-pressure helium is used to vent liquid oxygen through the thruster exhausts while hydrogen is allowed to boil off through the fill/drain valves.

In case of a hydraulic failure, the SSMEs can neither be gimbaled nor can their valves be changed. Each of the three hydraulic systems operated the valves of one engine, and each engine gimbal is supported by two hydraulic systems (i.e. it takes two failures to disable gimbal on one engine, but each hydraulic failure will disable valves on one engine).

If the valve settings can no longer be changed, the engine can still continue to run, but it can't be throttled any more, a condition known as 'hydraulic lockup'. It is still possible to shut down such an engine using pressure from the helium system though. Similarly, if sensors monitoring combustion chamber conditions or the command path from guidance computer to engine controllers fail, the engine is in a condition called 'electric lockup' - the controller will continue to operate it with the last known settings. Locked-up engines usually need to be shut down manually using the cutoff switches about 30 seconds prior to nominal MECO.

As of June 2015, the MPS is modeled in a good amount of detail, including most of the relevant valve settings, hydraulic and electric lockup, power failures on the engine controllers and the propellant dump sequence. The in-sim checklists provide instructions on how to execute the propellant dump and how to safe the engines for orbital operations.

=== Mechanical Systems ===

The Shuttle uses electromechanical actuators to move components which do not require hydraulic power. This includes the ET umbilical doors and the payload bay door. Each actuator contains two separate motors for redundancy, and transition time for any motion doubles if a motor is non-functional. The movement of these components is not time-critical, and hence usually slow - the complete payload bay door opening sequence takes about four minutes at normal speed to execute, twice that for actuator failures.

The ET umbilical doors are open at launch to allow the oxidizer and fuel feedlines to enter the orbiter, and they need to be closed after reaching orbit for the thermal protection during entry to be efficient. The payload bay doors are closed during ascent and entry and only opened in orbit. This is crucial, as the freon cooling loop radiators are located on the inside of the payload bay doors, i.e. the Shuttle can not remain indefinitely in orbit without opening the payload bay.

Opening or closing mechanical components usually involves unlatching, moving and possibly re-latching the components.

As of June 2015, the normal operation of ET umbilical door and payload bay door is implemented, but no actuator failures. The sequences can be driven from the GUI in automatic mode, but there is in principle support to drive them in manual mode as well as described in the Shuttle Crew Operations Manual.

Note that there's cross talk between mechanical systems and thermal modeling - tension building in the Shuttle due to uneven heating of the left and right fuselage can prevent the payload bay doors from opening or closing for instance.

== Guidance systems ==

=== Automated flight ===

Automated flight is available for all nominal mission phases except for the final approach and touchdown (for which in reality no AP is available either) as well as all single engine loss intact ascent aborts and all two engine out contingency aborts ending in either emergency landing or crew bailout.

Unlike an airplane which is usually in or close to a steady-state equilibrium (level flight at cruise altitude) when under AP control, this is almost never the case for the Shuttle. Thus, the AP requires a context to work properly - whether a current state vector is good or bad depends on what one wants to achieve. Usually this context is a guidance target (i.e. a desired orbit, a landing site, an abort MECO condition,...) and if no such target is provided, the AP will not engage.

If there is a valid guidance target, the PFD will display error needles even if the AP is disengaged which reflect what the AP would try to do in the current situation which can be used for manual piloting. The AP can be used separately in the pitch and yaw/roll axis and independently for throttle/speedbrake control.

Once disengaged, it is as a rule not wise to re-engage the AP if the Shuttle has deviated too much from the intended state. Many AP stages are based on closed loop guidance and will try to steer back to the desired solution, however this may not be possible.

Also, automated flight does not mean the pilot can lean back and the Shuttle will handle all aborts on its own - some AP modes specifically need to be engaged or augmented by DPS options to properly work - see the Crew Operations Manual for detailed instructions. In particular, if in an emergency the wrong AP mode is engaged, the Shuttle may try to solve a kinematically impossible maneuver which usually results in loss of control.

Finally, do not expect miracles from the AP. It will usually save the orbiter even after the loss of two engines, but it may not always on its own find a viable solution to a landing site in an abort scenario. In general, automated flight is much better at manging the instantaneous state (holding an alpha schedule, aiming at a waypoint) than at longer-term planning (managing gliding range after an abort,...).

Different from the powered and gliding phase, the orbital DAP contains automatic routines for attitude management - pointing the Shuttle, tracking a location or a celestial object or automated OMS burn maneuvers.

Operating the Shuttle AP properly is very different from operating airplane APs and requires a profound knowledge of OPS sequences and major mode transitions as well as strict adherence to the published procedures.

=== Ascent guidance Powered Explicit Guidance (PEG) ===

{{note|Full explanations about the Ascent guidance might be found there: [[Shuttle guidance - Ascent guidance Powered Explicit Guidance (PEG)]]}}

The purpose of this section is to present and discuss about the second stage ascent guidance (post SRB sep) for Nominal Orbital Insertion, and some Intact Aborts (TAL / AOA / ATO).
The guidance is based on the real closed loop used in the Shuttle, known as Power Explicit Guidance https://www.orbiterwiki.org/wiki/Powered_Explicit_Guidance.

'''Documentations'''

*A very detailled and complete topic about the guidance by Noiredd who implemented it in Matlab and KSP: https://github.com/Noiredd/PEGAS-MATLAB/blob/master/docs/upfg.md
*A deeper document with nice schematic drawings: Ascent Guidance Navigation and Control Shuttle Workbook (page 111) https://www.google.com/search?client=firefox-b-d&q=ascent+guidance+workbook+shuttle
*Original formulation of the Unified Power Explicit Guidance with equations and algorithms: ''ntrs.nasa.gov/citations/19740004402''
*A paper about enhancements made over the years to the original ascent guidance: ''ntrs.nasa.gov/citations/20180002035''

'''Overview'''

Second stage guidance functions very differently from first stage guidance in that second stage guidance is closed loop. Second stage guidance computes the control variables (essentially commanded attitude and attitude rates) and burn time to go (TGO) in such a way that the vehicle flies from the current state to the prescribed target conditions (altitude, velocity, flight path angle, and orbit plane) within trajectory constraints. It solves this two point boundary value problem each cycle (every 1.92 seconds). One limitation of second stage guidance is that it doesn't calculate if there is enough propellant to reach the desired MECO conditions.
[[File:PEG Meco target.webp|400px|thumbnail|none]]

The powered explicit guidance (PEG) scheme used by second stage guidance nominally operates in two phases. The first phase computes throttle and attitude commands based on three SSMEs and a constant thrust requirement until an acceleration of 3g is reached. At that time, the second phase, which uses variable throttle to maintain a constant acceleration, is entered. If an engine failure is detected, a third phase of PEG, which computes the necessary guidance commands using constant thrust to aim for the desired targets using two SSMEs, is entered (assuming no RTLS or TAL abort).

During current shuttle operations, only two phases of PEG are used, constant thrust through 3g and then variable thrust through main engine cutoff (MECO). STS-1 and STS-26, in order to prevent or reduce abort gaps, flew higher than normal trajectories, called lofted or abort shaped. This method required the third PEG phase, which ran from SRB sep to T_FAIL (I-loaded MET) and achieved lofting by assuming that an engine would fail causing loss of performance at the time T_FAIL. When T_FAIL occurred, PEG stopped assuming that an engine would fail. A drawback with this method was discovered later, however. The lofted trajectories caused “black zones,” or regions where an unsurvivable entry/pullout condition would be created if two engines actually did fail (CA). For this reason and the fact that abort shaping costs thousands of pounds of nominal ascent performance (payload), the I-load, T_FAIL is now set to zero, and lofted trajectories are not currently planned.
[[File:PEG step.webp|600px|thumbnail|none]]

Second stage guidance performs yaw steering to achieve the desired orbit plane. The desired orbit plane is defined by the unitized negative angular momentum vector (I-loads), commonly referred to as the '''IY vector'''. The x and y components of the IY vector define the nodal crossing, while the z component defines the inclination. For missions which do not involve rendezvous with a vehicle already in orbit (referred to as the “target”), the IYs are defined during the flight design process approximately 6 months prior to launch. These missions employ “earth fixed” yaw steering since the trajectory relative to the earth remains the same regardless of launch time. In order to successfully launch into orbit and rendezvous with another vehicle already in space, the orbiter must end up in the same orbital plane and altitude as the other vehicle.
[[File:PEG insertion.webp|600px|thumbnail|none]]

Forty seconds prior to MECO, guidance no longer seeks to achieve the altitude and orbital plane position targets. Common terminology is, “at MECO minus 40 seconds, the position constraints are released.” Without this constraint release, when TGO becomes small, a small change in position error would produce large changes in the thrust turning rate vector and over controlling would result. Note also that the cutoff time (TGO) calculation includes the predicted velocity change from the time minimum throttle is commanded to burnout. This corresponds to the predicted tailoff impulse from each active SSME and is known as fine count. Fine count occurs 10 seconds prior to MECO for nominal ascent, ATO, and TAL and 6 seconds prior to powered pitchdown for RTLS. It is at fine count where second stage, closed loop guidance is terminated and the SSMEs are commanded to a lower power level, usually 67% for three engines running or 91% for one or two engines running (note that the SSMEs aren't throttled back until powered pitchdown during an RTLS). Thereafter, the flight path angle constraint is released, such that TGO is computed solely on the desired velocity change (VGO). When guidance sees the shuttle at the correct inertial velocity (VI), all SSMEs are commanded to shut down.

=== Entry guidance algorithm ===

{{note|Full explanations about Entry shuttle guidance might be found there: [[Shuttle guidance - Entry guidance algorithm]]}}

A topic speaking about the entry guidance algorithm.

'''Documentations'''

I didnt use hyperlinks to avoid NASA ntrs server spam from forum robots

*A quick overview of the Descent guidance from the Space Shuttle Technical Conference: ''ntrs.nasa.gov/citations/19850008593''
*A deeper look into the Entry equations formalism with that paper that you might find under: ''Shuttle Entry Guidance JSC-14694 ''
*Entry guidance formulation requirements (code): ''ntrs.nasa.gov/citations/19800016873''

All the documentations linked in the Entry/TAEM rework are even more useful now, as almost all the parts of Entry guidance are simulated and displayed parameters fed with consistent datas.
https://forum.flightgear.org/viewtopic.php?f=87&t=38777

=== TAEM/Approach guidance algorithm ===

{{note|Full explanations about TAEM and Approach/Autoland guidance might be found there: [[Shuttle guidance - TAEM/Approach and Autoland guidance]]}}

This section speaks about TAEM and Autoland guidance.

'''Documentations'''

*Space Shuttle TAEM guidance code sum up: [https://ntrs.nasa.gov/citations/19920010688]
*TAEM/Approach Handbooks there: [https://forum.flightgear.org/viewtopic.php?f=87&t=38777]

'''Overview'''

The last link mentionned above is pretty interesting to see the evolution of TAEM guidance and how it was handled.
The main document I used include the Optional TAEM Targeting (OTT) logic that has been used since STS-5 (before the HAC was a circle with less Energy options for test flights).

After STS-5, HAC could be flown with the different options we are used to see .
Overhead or Straight-In HAC; and Nominal Entry Point (7Nm in final) or Minimal Entry Point (4Nm in final)
[[File:OTT option.webp|600px|thumbnail|none]]

Another option called - final radius shrinking - is included in that TAEM guidance version.
It allows the final HAC radius (2.3 Nm) to decrease up to 0.8 Nm if we are low during the HAC.
[[File:Spiral hac.webp|600px|thumbnail|none]]

The whole logic is organized through several functions that are called during all the TAEM phase at a rate between 160 and 980ms.
It ends at 10000 feet (Approach and Landing interface) where the Auto Land logic kicks in (quite the same logic with tighter gains).
[[File:TAEM flow logic.webp|600px|thumbnail|none]]

Let's go briefly through each functions.
The first function that is not mentionned is a frame coordinate converter from a Greenwhich frame into a runway centered frame.
[[File:TAEM runway coordinate system.webp|600px|thumbnail|none]]

== Avionics and DPS ==

The avionics of the Space Shuttle is fairly faithfully reproduced by the simulation, see the dedicated article on [[Space Shuttle Avionics]] for an overview. The implemented screens include routines to monitor the various systems as well as guidance navigation and control for all mission stages.

[[File:GNC_sys_summ_up_2.jpg|600px|thumbnail|none|GNC SYS SUMM 2 display of the Space Shuttle]]

All nine MDUs of the forward panel are usable and display the DPS and MEDS screens of the Shuttle - this includes launch and entry guidance routines, TAEM guidancs as well as orbital tracking and pointing management. In addition, HUDs for Commander and Pilot are provided.

[[File:Shuttle_cockpit_OPS_2_day.jpg|1000px|thumbnail|none|Space Shuttle cockpit Day]] [[File:Shuttle_cockpit_before_launch.jpg|1000px|thumbnail|none|Space Shuttle cockpit Night]]

An alternative display for all phases of flight is provided by the FG-native the HUD. This has four different modes - ascent, orbit, entry and approach, and dependent on the HUD mode, different information relevant for the mission phase is displayed. In all cases, the current CSS DAP is identified in the upper left.

There is a calculator for orbital elements available, determining perigee and apogee, orbital inclination and longitude of the ascending node (the latter is currently not so useful as it is obtained in an inertial coordinate system). Based on these orbital elements, the groundtrack map displays current position of the Space Shuttle, selected landing site, ground track history and a prediction of the future orbit - if the perigee is below the surface of Earth, the prediction ends at the estimated ballistic impact point (note that due to the aerodynamical capabilities of the Shuttle, the actual landing site can be within a cross range of about 1000 miles around that point dependent on how the trajectory is managed during the entry phase).

== Payload handling ==

The Space Shuttle is equipped with the capability to release payload from the bay into space, or to catch a payload from space and deposit and secure it in the bay. For this, the Remote Manipulator System (RMS) arm in combination with the payload retention system is used.

[[File:Hubble docked.jpg|600px|thumbnail|none|Handling a payload with the RMS arm]]
[[File:Hubble COAS.jpg|600px|thumbnail|none|Hubble through COAS system]]
[[File:Hubble_grapple.png|600px|thumbnail|none|Handling Hubble with the RMS arm]]

=== RMS arm operation ===

The RMS arm is a fairly complicated device with six different joints, each allowing rotation along one specific axis, which is formed after the human arm. The nomenclature is borrowed from this analogy, so there is a shoulder yaw, a shoulder pitch, an elbow pitch, a wrist pitch and wrist yaw and roll joints. Each of the joints can only be moved a certain angular range. At the end of the RMS arm is the end effector which is the device which can attach to a payload.

The RMS arm can be driven in various modes. The simplest of these are the single joint or the direct mode in which each joint angle is controlled separately, i.e. the arm is extended by first selecting a joint, then commanding it to either increase or decrease angle, before the next joint is selected.

Since this is cumbersome, the more natural control modes allow to use the stick (or whatever control device is attached) to directly move a reference point. In the ORB UL x/y/z mode (UL stands for 'unloaded') the reference point is the tip of the end effector, i.e. using the stick just moves the joint angles such that the end effector moves along the x, y, or z-axis and otherwise keeps its attitude. The ORB UL yaw/pitch/roll mode in contrast keeps the end effector's position and just changes its attitude.

The real Shuttle has additional modes in which the reference point is in the center of the payload, or in which the reference coordinate system is changed from the Shuttle's coordinate system to a system co-moving with the end effector camera - these are as of August 2015 not implemented in FG.

All modes except single and direct joint driving have software safety stops when the joints approach their limit extensions. Since in its stowed position, two of the joints are in the software stop region, it is necessary to directly drive shoulder pitch and elbow pitch out of their soft stop region to be able to use the more sophisticated control modes - see the diagram below for the reach angles of each joint.

[[File:Joints.gif|600px|thumbnail|none|RMS arm reference coordinate system and joint reach angles]]

Finally, the RMS arm is secured by a shoulder brace to make it cope with launch acceleration. This brace needs to be removed before the arm can be operated, and the arm itself needs to be powered, deployed and unlatched.

=== Payload retention system ===

The payload retention system is a series of latches which hold a payload in the bay. Before a payload can be lifted out of the bay, these latches need to be released. Similarly, if a payload is returned into the bay, ready-to-latch indicators show when it has reached the correct stowing position and it can only be safely released from the RMS arm once the latches are closed.

The real Shuttle has three different payload positions with corresponding latch controls, as of August 2015 only one payload position is supported in FG. Likewise, currently only a simple demo satellite with no proper folding/unfolding animation is available as visual payload (note that a payload mass affecting the FDM can also be chosen in the 'Fuel and Payload' dropdown menu).

== Mission phases ==

The various phases of a Shuttle mission are generically subdivided into launch, orbit, entry, TAEM and approach. These can directly be accessed by appending the mission phase to the command line. This will automatically start the Shuttle in the correct configuration and the correct state for the mission selected. For instance, --aircraft=SpaceShuttle-TAEM --airport=KVBG will initialize a TAEM approach into Vandenberg, --aircraft=SpaceShuttle-orbit --lat=30.0 --lon=0.0 --heading=90.0 will initialize the Shuttle in a 30 deg inclination orbit.

Note that --aircraft=SpaceShuttle-entry combined with an airport as location will ''not'' initialize you on an entry trajectory to that airport since the entry interface is several thousand miles away from the landing site and moreover the trajectory needed is not unique but depends on what you fly - you need to initialize the entry interface location by hand using latitude and longitude.

Specific information on the mission phases can be found in the following articles:

=== Documentations ===

[[Flying the Shuttle - Space Shuttle Checklists]]

=== Nominal Operations ===

[[Flying the Shuttle - Launch]]

[[Flying the Shuttle - Orbital Operations]]

[[Flying the Shuttle - Entry]]

[[Flying the Shuttle - Final Approach]]

=== Nominal Operations Advanced Tutorial ===

[[Flying the Shuttle - Launch And Post Insertion Advanced]]

[[Flying the Shuttle - Deorbit Preparation Advanced]]

[[Flying the Shuttle - Deorbit Burn and Final Entry Preparation Advanced]]

[[Flying the Shuttle - Entry TAEM and Landing Advanced]]

=== Intact Aborts ===

[[Flying the Shuttle - Intact Abort Procedures Overview]]

[[Flying the Shuttle - Return To Launch Site RTLS]]

[[Flying the Shuttle - Transoceanic Abort Landing TAL]]

== Glossary of acronyms ==
{|
| '''AoA''' || Angle of Attack
|-
| '''APU''' || Auxiliary Power Unit
|-
| '''CoG''' || Center of Gravity
|-
| '''CSS''' || Control stick steering
|-
| '''DAP''' || Digital autopilot
|-
| '''ET''' || External tank
|-
| '''EVA''' || Extravehicular Activity (spacewalk)
|-
| '''FC''' || Fuel cell
|-
| '''FCS''' || Flight Control System
|-
| '''ISP''' || Specific impulse
|-
| '''MECO''' || Main Engine Cutoff
|-
| '''MMH''' || monomethylhydrazine (a propellant)
|-
| '''MMU''' || Manned Maneuvering Unit
|-
| '''MPS''' || Main Propulsion System
|-
| '''OV''' || Orbiter vehicle
|-
| '''OMS''' || Orbital Maneuvering System
|-
| '''PRL''' || Priority Rate Limiting
|-
| '''RCS''' || Reaction Control System
|-
| '''RHC''' || Rotational Hand Controller
|-
| '''RMS''' || Remote Manipulator System
|-
| '''SRB''' || Solid rocket booster
|-
| '''SSME''' || Space Shuttle main engine
|-
| '''TAEM''' || Terminal Area Energy Management
|-
| '''THC''' || Translational Hand Controller
|-
| '''TVC''' || Thrust Vector Control
|}

== Latest development snapshot ==
The latest development version (possibly unstable) is found in a dedicated [https://sourceforge.net/projects/fgspaceshuttledev/ repository] on SourceForge. You can download the latest snapshot from http://sourceforge.net/p/fgspaceshuttledev/code/ci/development/tarball. Stable updates are pushed to FGAddon periodically.

== Documentation ==

In addition to the original NASA Shuttle Crew Operations Manual and the DPS dictionary which are found in the Documentation/ folder of the spacecraft, a Flight Manual specifically for the operation of the Flightgear simulation is available (standard edition free of charge for Flightgear users):

[[File:Flight manual standard.png|400px|link=http://www.science-and-fiction.org/bookstore.html|alt=Shuttle flight manual|Title Flight Manual]]

(click picture to download)

== Educational Links / Shuttle technical files ==

=== General Space knowledge and tutorials ===

''Basic of Space Flight Book''
https://er.jsc.nasa.gov/seh/spaceflt.pdf

''Thorsten LEO Tools''
https://forum.flightgear.org/viewtopic.php?f=87&t=35213

''Orbiter Space Sim Beginners tutorial''
https://www.youtube.com/watch?v=bOxpvqrqLAo

''FAA Space Basics ( Must read)''
https://web.archive.org/web/20210530202242/https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/cami/library/online_libraries/aerospace_medicine/tutorial/section3/spacecraft_design/

''Rendez Vous Theory''

https://www.baen.com/rendezvous
https://www.baen.com/rendezvous-part2

''Educative links''

Why the wings of the Shuttle Stay on it during Maximal Aerodynamical pressure phase
https://www.aiaa.org/docs/default-source/uploadedfiles/about-aiaa/history-and-heritage/why_the_wings_stay_on-ehrlich.pdf?sfvrsn=801c62b5_0

Space Shuttle Aerodynamics and Flight Dynamics Overview
https://web.archive.org/web/20210127120052/https://www.nasa.gov/centers/johnson/pdf/584730main_Wings-ch4d-pgs226-241.pdf

=== Space Shuttle Systems ===

'''Space Shuttle Systems in depth'''

''Nasa Space Shuttle systems Exhaustive Manual: SCOM''
https://web.archive.org/web/20200602210929/https://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf

''Nasa Data processing system dictionnary, or "What does that page of my shuttle computer"''
https://web.archive.org/web/20210226022241/https://www.nasa.gov/centers/johnson/pdf/359895main_DPS_G_K_7.pdf

''Crew Software Interface ( Nice introduction to Shuttle Computer and handling)''
https://web.archive.org/web/20210226022249/https://www.nasa.gov/centers/johnson/pdf/383444main_crew_software_interface_21002.pdf

'''Workbooks ( Detailled part on some Shuttle systems and procedures, SCOM complement)'''

''APU (How Hydraulic is provided to Shuttle systems''
https://web.archive.org/web/20210226022251/https://www.nasa.gov/centers/johnson/pdf/383439main_apu_hyd_wsb_21002.pdf

''Air Data Systems (What are the equivalent of Pitot Tubes in the Shuttle)''
https://web.archive.org/web/20210226021921/https://www.nasa.gov/centers/johnson/pdf/383438main_air_data_system_workbook_21002.pdf

''Environmental Control and Life Support System ( How is cooled the Shuttle )''
https://web.archive.org/web/20210226004654/https://www.nasa.gov/centers/johnson/pdf/383445main_eclss_21002.pdf

''Navigation Aids ( or how the Shuttle find precisely the runway during entry)''
https://web.archive.org/web/20210226022247/https://www.nasa.gov/centers/johnson/pdf/383450main_navigation_aids_workbook%2021002.pdf

''Intact Ascent Aborts ( Procedures after ONE engine failure)''
https://web.archive.org/web/20210226022307/https://www.nasa.gov/centers/johnson/pdf/383447main_intact_ascent_aborts_workbook_21002.pdf

''Contigency Aborts Procedures after more than ONE engine failure/degradation''
https://web.archive.org/web/20210226011554/https://www.nasa.gov/centers/johnson/pdf/383441main_contingency_aborts_21007_31007.pdf

''And much more that are not publicly available but findable here after a subscription ( A true Space Gold Mine)''
https://www.nasaspaceflight.com/l2/

=== Space Shuttle Checklists ===

''Flight Data Files Bible Site''
https://web.archive.org/web/20211020173004/https://www.nasa.gov/centers/johnson/news/flightdatafiles/index.html

''Annotated and condensed one''
[[Flying the Shuttle - Space Shuttle Checklists]]

A bit more organized:

More informations about Flight Data Files in SCOM part 3

'''Normal situation Checklists'''

''Ascent''
https://web.archive.org/web/20210406234707/https://www.nasa.gov/centers/johnson/pdf/567068main_ASC_135_F_1.pdf

''Post Insertion''
https://web.archive.org/web/20210417211853/https://www.nasa.gov/centers/johnson/pdf/567074main_PI_135_F.pdf

''On Orbit''
https://web.archive.org/web/20210417205430/https://www.nasa.gov/centers/johnson/pdf/567072main_ORB_OPS_135_F_1.pdf

''Rendez Vous''
https://web.archive.org/web/20210417202323/https://www.nasa.gov/centers/johnson/pdf/567076main_RNDZ_135_F.pdf

''Deorbit Preparation''
https://web.archive.org/web/20210424062634/https://www.nasa.gov/centers/johnson/pdf/492871main_D-O_G_Q_5.pdf

''Entry''

https://web.archive.org/web/20210424062633/https://www.nasa.gov/centers/johnson/pdf/381558main_ENT_G_H_8.pdf
https://web.archive.org/web/20210417204127/https://www.nasa.gov/centers/johnson/pdf/567069main_ENT_135_F.pdf

'''Non Normal situation Checklists'''

In the Normal situation Checks above, there are off nominal sections to deal with non critical procedures.

For time critical procedures that must be performed within 5 minutes, there are the so called Pocket checklists ( Ascent, Orbit and Entry).
They are almost the same.

''Ascent''

The Ascent PCL contains procedures that safe systems for continued flight. It also contains orbiter systems powerdown procedures.
https://web.archive.org/web/20210407003811/https://www.nasa.gov/centers/johnson/pdf/366508main_APCL_G_O_1.pdf

''Orbit''

At the initiation of the post insertion phase, the Orbit PCL is utilized. This PCL contains critical orbiter systems malfunction responses and powerdown procedures. The orbit PCL often refers to the orbiter Malfunction Procedures (MAL) Book for detailed troubleshooting.

https://web.archive.org/web/20210907221523/https://www.nasa.gov/centers/johnson/pdf/359853main_OPCL_G_M_10.pdf

Contigency Deorbit in case of Severe malfunctions in Orbit ( Loss of cooling systems, or massive elec failure,..) that would lead to a fast deorbit.

https://web.archive.org/web/20210417212721/https://www.nasa.gov/centers/johnson/pdf/359894main_C-DO_G_L_8_P%26I.pdf

''Entry''

The Entry PCL contains critical contingency systems malfunction responses that allow safe continuation of the pre-deorbit through early entry phases along with orbiter systems powerdown procedures.

https://web.archive.org/web/20210424062636/https://www.nasa.gov/centers/johnson/pdf/366509main_EPCL_G_M_11.pdf

=== Space Shuttle Books ===

''To Orbit and Back Again''

Like a SCOM, less cryptic, full of anecdotes.
https://www.springer.com/gp/book/9781461409823

''Into to the Black''

Book about STS 1, it reads like a Thriller
https://www.thespacereview.com/article/2982/

''Shuttle Down''

Book about an hypothetical scenario. What if the Shuttle was launched from vandenberg and would have diverted to Easter Island :)
[url]https://www.goodreads.com/book/show/549127.Shuttle_Down[/url]

== Videos ==

A compilation of in FG Sim videos about the Space Shuttle

[https://www.youtube.com/watch?v=LOpKt2gXQoE Space Shuttle Launch Flight Gear with STS 133 Real Voices]

[https://www.youtube.com/watch?v=bDGIZj4GGxg Space Shuttle RTLS Abort with OPS 6 real guidance]

[https://www.youtube.com/watch?v=ECJjC-i_3l8 Space Shuttle TAEM KSC Runway 33:HAC and Final Approach]

[https://www.youtube.com/watch?v=fbTFKBWYGbE Space Shuttle TAL]

[https://www.youtube.com/watch?v=62ylBBeO-z4 Space Shuttle Autoland in fog]

On orbit timelapse
[https://forum.flightgear.org/viewtopic.php?f=19&t=35234]

== Mission reports ==

A compilation of Space Shuttle stories / mission reports.

''Shuttle approaches contest''
[https://forum.flightgear.org/viewtopic.php?f=19&t=32790]

''The Van Allen Mission''
[https://forum.flightgear.org/viewtopic.php?f=19&t=35011]

''STS 62 Polar Mission''
[https://forum.flightgear.org/viewtopic.php?f=87&t=38916]

''Meeting ISS''
[https://forum.flightgear.org/viewtopic.php?f=19&t=35276]
[https://forum.flightgear.org/viewtopic.php?f=19&t=35316]
[https://forum.flightgear.org/viewtopic.php?f=19&t=35535]

''Meeting Hubble''
[https://forum.flightgear.org/viewtopic.php?f=87&t=36311]

''From Ground to Orbit''
[https://forum.flightgear.org/viewtopic.php?f=19&t=32851]

''From Orbit to Ground''
[https://forum.flightgear.org/viewtopic.php?f=19&t=33167]

''Return to Launch Site''
[https://forum.flightgear.org/viewtopic.php?f=19&t=33030]

''Transoceanic Abort Landing in Zaragoza''
[https://forum.flightgear.org/viewtopic.php?f=19&t=33368]

''Abort Once Around''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34315]

''Contingency Abort: Landing in Bermuda''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34254]

''Contigency Abort: East Coast Abort Landing''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34969]

''Electrical failure and TAL''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34810]

''Impending Loss of Hydraulics and AOA''
[https://forum.flightgear.org/viewtopic.php?f=19&t=35048]

''Fictionnal Mission into Polar Orbit from Vandenberg''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34700]

''Deorbit and Landing in Easter Island''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34229]

''Triple Engine Failure TAL''
[https://forum.flightgear.org/viewtopic.php?f=19&t=35763]

''Massive electrical failures and Contigency Deorbit // Off Nominal Checklist walkthrough''
[https://forum.flightgear.org/viewtopic.php?f=87&t=36862]

''Single Engine TAL after Droop''
[https://forum.flightgear.org/viewtopic.php?f=87&t=40479]

== Gallery ==
{{screenshot cat
| category = Space Shuttle screenshots
| subject = the Space Shuttle
| image = Shuttle FG03.jpg
}}{{-}}
<gallery mode="packed">
KSC_launch_photorealism.webp|KSC launch photorealism
KSC_launch_2_photorealism.webp|KSC launch photorealism
Vandenberg_photorealism.webp|Vandenberg site photorealism
White_sands_photorealism.webp|White Sands site photorealism
Edwards_photorealism.webp|Edwards site photorealism
Bermuda_photorealism.webp|Bermuda site photorealism
Pad_view_inside.jpg|View on the Pad Pilot Side
Rainy_Pad.jpg|Rainy Pad
On_the_pad.jpg|Shuttle Launch
Shuttle_Launch.jpg|Shuttle Launch
Shuttle FG04.jpg|Shuttle Launch
Farewell.jpg|Launch smoke trail
SRB_sep.jpg|SRB separation
Orbital_Speed.jpg|Accelerating to orbital speed
SSME.jpg|Improved visuals of the exhaust flame
The_desk.jpg|Shuttle 3d cockpit
MECO_sep.jpg|External tank separation
On_orbit_view.jpg|A view of Earth after reaching orbit
ET_sep_2.jpg|The ET seen from the Shuttle
Shuttle OMS full.jpg|Full OMS thrust
Light_effect.jpg|Lightings game in Orbit
Shadow_3.jpg|Shadows and lights on the L2 Commander panel
Over_Africa.jpg|The orbiter high over Africa
Payload ops03.jpg|Handling payload with the RMS arm
Payload_lighting.jpg|Payload Lightings
Space Shuttle sunrise.jpg|Sunrise over Antarctica
Over_Antartica.jpg|Sunrise over Antarctica 2
Sunset.jpg|The OV in orbit at Sunset
Sunset_2.jpg|The OV in orbit at Sunset 2
Sunset_rtls.jpg|RTLS Abort
OMS_burn.jpg|Orbital insertion burn at night
Shuttle-landing04.jpg|Atmospheric entry
Glowing_red_2.jpg|Tiles Glowing Red
Roll_reversal.jpg|High bank angle maneuver to control vertical speed
Mach_down.jpg|During TAEM the Space Shuttle goes subsonic
Eastern_Island_approach.jpg|On final approach into Eastern Island Emergency Landing Site
Final_approach_trondheim.jpg|Final in Trondheim
Pre_flare_KSC.jpg|Pre-flare
Flare_KSC.jpg|Flare
Touch_KSC.jpg|Touchdown in KSC
Fin.jpg|Wheels stop in KSC
</gallery>

[[Category:Space Shuttle documentation]]

Space Shuttle

2024-11-21T18:04:25Z

Gingin: /* Guidance systems */

{{:{{PAGENAME}}/info}}
{{hatnote|See also [[Space Shuttle (FG Space Program)]] for the other Space Shuttle.}}
[[File:Spacetripready.png]][[File:Checklistready.png]]

{{Space Shuttle navigation}}

The NASA '''Space Shuttle''' was the world's first operational space plane capable of reaching orbit. It was operated from 1981 to 2011 on a total of 135 missions during which two orbiters, Challenger and Columbia, were lost in accidents.

The Shuttle launch system components include the Orbiter Vehicle (OV), a pair of solid rocket boosters (SRBs) and the external tank (ET) containing the liquid hydrogen and oxygen fuel for the engines of the orbiter. Of these, only the external tank is expendable; the SRBs splash into the sea shortly after launch and are recovered, and the orbiter itself returns to a landing site where it lands like an airplane.

The mixture of a rocket-like launch, a spacecraft-like near ballistic early atmospheric phase and an airplane like approach and landing makes the Space Shuttle a truly unique flying experience.

== Project Aim ==

The aim of the Shuttle Project is to create a highly realistic simulation of the capabilities of the Space Shuttle in FlightGear. While most of the time the real Shuttle is under the control of automatic guidance systems, there are fallback modes to control the spacecraft manually, the so-called CSS (control stick steering) modes, and it is these modes we primarily try to implement.

In addition to the real avionics and control modes, the idea is also to provide various 'educational' modes and instruments in order to explore and appreciate certain aspects of a Shuttle mission more.

The [http://ntrs.nasa.gov NASA technical reports server] supplies a large base of wind tunnel and in-situ performance data of both the mated launch vehicle and the orbiter, and the aerodynamics of the simulated shuttle is based on these documents. The authoritative source for procedures for trajectory management, instrumentation, limits and emergency procedures is the [https://web.archive.org/web/20200602210929/https://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf Space Shuttle Crew Operations Manual] and currently a normal mission, i.e. ascent, orbital insertion, de-orbit, entry, terminal area energy management and landing can be flown largely 'by the book', i.e. following the real procedure for CSS.

In the following, descriptions refer to the development version - the last stable or the release version may not have all features described.

=== Limit and failure modeling ===

The project contains code to simulate the various structural and aerodynamical limits as well as component failures based on sections 4 and 6 of the Space Shuttle crew manual.

The general philosophy on limit modeling is that they can be treated dependent on a user setting as 'soft', 'hard' and 'realistic'. Where applicable, warnings when the state of the orbiter is getting dangerously close to a limit are called out in addition to a recommendation how to deal with the situation. Dependent on the trajectory of the orbiter, there may or may not be sufficient time to redeem the situation.

; soft
: Limit violations are called out, but their violation has no consequences for aerodynamics or component failures.

; hard
: Any limit violation immediately ends the simulation.

; realistic
: In reality, components do not necessarily fail immediately if used outside their design specs. This option applies a probabilistic failure model in which the chance for a component to fail grows with the degree of limit violation. The failure may or may not be immediately visible, e.g. too much qbar upon ascent may damage the heat shield, but this may not be apparent (unless specifically checked) until the heat shield fails upon atmospheric entry.

Component failure is modeled gradually where applicable - while a tire can only blow or not blow, an airfoil or a thruster for instance may lose a certain percentage of its efficiency.

In addition to failures induced by limit violations, the simulation also supports failure scenarios designed to model typical failure modes which could be expected to occur during operations, such as for instance engine failures or lock-up on ascent, coolant loop failures or leaks or similar. Rather complex chains of failures are modeled, for instance a failure of a coolant water spray boiler will lead to subsequent overheating of an APU unit - if this is not realized and proper action taken, the APU will fail subsequently, causing in turn a failure of one hydraulic system which potentially causes downstream failures of airfoil actuators or main engine gimbal capability.

== The mated launch vehicle ==

At liftoff, thrust for the shuttle is provided by its three main engines (SSMEs) and the two SRBs. The assembled launch configuration has a height of 184.2 ft (56.1 m) and a mass of about 4,470,000 lb or 2.030 tons (in addition to payload), over 90% of this being propellant. The main engines would at this point be incapable of lifting the launch stack.

The SRBs burn an ammonium perchlorate composite fuel with a relatively low ISP of 268 s in vacuum, supplying 2,800,000 lbf of liftoff thrust each, this is supplemented by the SSME burning liquid hydrogen/oxygen with an ISP of 455 s, supplying an additional total liftoff thrust of 1,180,000 lbf. At liftoff, the shuttle hence reaches a thrust/weight ratio over 1.6, i.e. it leaves the launch pad rapidly.

Control during ascent is provided by thrust vectoring of both the SRB and SSME nozzles. The real-world CSS scheme is a 'stick controls rates' scheme which for stick to neutral does 'attitude hold' which makes it possible to control the launch trajectory very precisely.

=== The Solid Rocket Boosters ===

Each SRB weighs about 1,300,000 lb, out of which 1,100,000 is propellant weight. The propellant of the SRBs is shaped to provide a high liftoff thrust, followed by a thrust reduction during the phase of the highest dynamical pressure (max. qbar). The actual thrust as a function of time is fairly complicated:

[[File:SRB thrust.png|400px|thumb|none|Thrust characteristics of the Space Shuttle Solid Rocket Boosters]]

The distribution is faithfully modeled in FG and the definitions to match the real thrust characteristics is taken from the [http://jsbsim.sourceforge.net/download.html JSBSim code repository]

The SRBs can not be throttled, once ignited, they provide thrust as explained above. SRB ignition takes place some three seconds after main engine ignition, and once they ramp up to full thrust, the shuttle has no choice but to leave the launch pad. For thrust vectoring, SRB nozzles can be gimbaled up to 8 deg in both pitch and yaw axes, a roll moment is created by gimbaling the two SRBs in opposite directions.

[[File:SRB 2.jpg|800px|thumbnail|none|Early ascent on combined SRB and SSME thrust]]
[[File:Sonic boom.webp|800px|thumbnail|none|Sonic boom and max dynamical pressure]]

As of May 2015, SRB separation happens automatically once the thrust drops below some threshold to avoid having to drag dead weight, but there is no provision to manually separate. The SRBs are pushed away from the remaining launch vehicle by separation motor burns. These (including the separation animation with still burning SRBs) are modeled in FG, however due to technical issues with the submodel code at high velocities, thrust of the separation motors in the sim is set larger than in reality to provide the same visual separation dynamics.

The SRBs are implemented as ballistic submodels, i.e. they follow a correct trajectory and ascent with the shuttle, however since (unlike the shuttle) they are not accelerating, they visually fall behind quite quickly.

=== The Main Engines ===

The three main engines (SSMEs) are used during ascent and burn propellant from the ET. They are mounted in a triangular configuration at the stern, tilted by 13 degrees with respect to the spacecraft main axis and can be gimbaled by 10.5 degrees in the pitch and by 8.5 degrees in the yaw axis. The reason for the tilted arrangement is to have a sensible CoG of the OV together with the ET during the later ascent stages. The heavy oxygen is stored forward in the ET, leading to a fairly forward CoG for the mated vehicle such that the SSMEs can be vectored through the CoG. This assembly is faithfully modeled in FG.

[[File:SSME.jpg|800px|thumbnail|none|Late ascent phase on SSME thrust]]

The engines can be throttled between 67 and 109% of rated power, this is necessary to keep the launch vehicle within structural limits during the high qbar phase in the atmosphere and later close to MECO as the propellant in the ET is almost depleted. Thrust increases during ascent as the exhaust gases do no longer have to push against an atmosphere. Both liftoff and vacuum thrust of the modeled engines are in agreement with published values.

Since the SSME's are mounted much closer to each other than the SRBs, the Shuttle loses significant yaw and roll maneuverability after SRB separation. However as the spacecraft is nearly out of the atmosphere by then, no such maneuverability reserves are actually needed.

In FG, the throttle controls all three SSMEs during ascent. Engines ignite once throttle is moved above 67%, this triggers the SRB ignition. If the throttle is moved below 67%, the engines will stop, however they will restart once throttle is moved again up as long as fuel is available in the ET.

The engine numbering by NASA has the center engine as number 1, the left engine as number 2 and the right engine as number 3 and these numbers are used in in-sim callouts of engine failures. For some failure modes, engines will not respond to throttle any more, in this case the cutoff switches have to be used. These are {{Key press|Control|q}} for engine 1, {{Key press|Control|w}} for engine 2 and {{Key press|Control|e}} for engine 3. An engine that has been shut down by the cutoff switch will not re-ignite.

The propellant for the SSMEs is carried in the ET. The tank has a liftoff weight of approximately 1,680,000 lb (760 tons) and a dry weight of about 66,000 lb (dependent on version - the Space Shuttle menu offers an option to fly older and heavier tanks). The ET is the only expendable component of the launch stack, it is dropped after MECO upon almost reaching orbit and then the shuttle uses the OMS to attain orbit while the tank re-enters the atmosphere half an orbit later and breaks up during entry.

[[File:Et_sep.jpg|800px|thumbnail|none|External tank separation]]

In FG, the tank is normally separated using {{Key press|d}}. This is vetoed if the Shuttle has unsafe yaw, pitch or roll motion in which case the RCS should be used to stabilize the orbiter before ET separation. If an emergency separation needs to be performed, {{Key press|Control|d}} overrides the veto. At separation, a translational RCS burn will automatically push the shuttle away from the tank.

After separation, the ET will approximately co-orbit with the OV, i.e. unless the Shuttle ignites the OMS engines, the tank will be visible for a long time, slowly drifting off, and it is quite possible to use the Shuttle's RCS engines to do a visual inspection of the tank.

[[File:ET_sep_2.jpg|800px|thumbnail|none|The ET seen from the Shuttle]]

=== A note on aerodynamics of the mated vehicle ===

With the ET and SRBs attached, the launch stack has quite different aerodynamical characteristics than the OV alone, for instance the stack is more yaw-stable than the orbiter and its pitching moment as function of alpha and rolling moment as function of beta are very different. Where such data could be obtained from wind tunnel tests with the mated stack, it has been used in the simulation.

As in reality, the simulated shuttle has an automated downward elevon deflection schedule with Mach number upon ascent to provide further load relief for the wings (with corresponding aerodynamical forces acting).

In general though, aerodynamical effects are subleading, the ascent dynamics is dominated by the thruster forces and the flight control systems have a large margin to compensate for them.

=== The Ascent Performances ===

Space Shuttle Main Engine thrust, [https://en.wikipedia.org/wiki/Specific_impulse ISP], and consumption is now within a percent of the real datas (Dev version of December 2020)
The mixture ratio in real was around 6, and it is what we observe in the sim (6 times more liquid Oxygen burnt than liquid Hydrogen). Hence, Main Engine Cut Off (MECO) time is matching real one. Plus, the propellant remaining at MECO, called the Final Performance Reserve (FPR) is now within a percent (15000 pounds). It makes launch with high payload into a high inclination Orbit (towards ISS typically) really interesting and limitating performance wise, like in real.

An interesting read about that FPR, written by a former Shuttle Flight Controller: [https://waynehale.wordpress.com/2014/10/08/understanding-sts-93-the-key-is-mixture-ratio/ Wayne Hale: The key is Mixture Ratio]

You can find below some in sim datas compared to real one coming from the Shuttle Crew Operations Manual (SCOM).

[[File:Stage_1_in_sim.png|600px|thumbnail|none|Stage 1 Velocity Vs Time in Sim]][[File:Stage_1_scom.jpg|600px|thumbnail|none|Stage 1 Velocity Vs Time in real]]
[[File:Stage_2_in_sim.png|600px|thumbnail|none|Stage 2 Velocity Vs Time in Sim]][[File:Stage_2_scom.jpg|600px|thumbnail|none|Stage 2 Velocity Vs Time in real]]

=== CSS DAP schemes for ascent ===

During ascent, the stick controls thrust vectoring for both SSMEs and SRBs. The following two DAP schemes are available:

; Thrust vectoring
: This is the real CSS ascent mode for the shuttle in which stick motion controls rate, stick to neutral commands an attitude hold. Internally a PID controller vectors the thrusters and uses the stick input as a bias for the error. This is a very stable scheme and can be easily used to achieve high precision in controlling ascent speed or orbital inclination.

; Thrust vectoring (gimbal)
: This is an educational scheme in which the stick motion directly controls the engine gimbal, i.e. the pilot needs to do the task of the PID controller himself. To make things somewhat easier, the engines are automatically vectored through the stack's CoG, i.e. outside the atmosphere stick neutral corresponds to zero moments acting on the stack. In the atmosphere, the control input hence needs to compensate for aerodynamical forces. Launch in this scheme is fairly rough and it is not possible to reach high precision, but it is possible to fly into orbit and gain a first-hand experience of the forces acting on the stack.

{{Key press|m}} switches between the ascent DAPs. {{Key press|Control|m}} switches from the ascent to the orbital DAP modes (do not use an orbital DAP for ascent control unless you know very well what you're doing).

=== Ascent structural and aerodynamical limits ===

The following structural and aerodynamical limits need to be observed during ascent:

* Dynamical pressure qbar < 819 lb/sqf (modeled)

This is a structural limit for the orbiter and mated stack, in actual operations the orbiter should be kept below 650 lb/sqf.

* Wing bending moment coefficient CBW between -0.019 and 0.019 at max. qbar (modeled)

At max qbar, the wing bending moment is a function of Mach number and AoA. Since Mach number is close to 1.4 in this phase of the flight, this limit basically translates into alpha between -8 degrees and 2 degrees. This can only be achieved if the orbiter is in inverted flight.

* Translational accelerations Nx between 0 and 3.11 g (modeled), Ny between -0.18 and 0.18 g (not modeled) and Nz between -0.06 and 0.73 g (not modeled).

These are structural limits of the mated stack to acceleration rather than aerodynamical forces. Especially the Nx (acceleration along the orbiter axis, i.e. main engine thrust) is important and requires to throttle down the SSMEs towards the end of the burn time.

* Late ascent trajectory may not drop below 265.000 ft (modeled)

This is a heat load limit for the external tank insulation, if the thermal protection of the ET fails, it will explode.

== The Shuttle in orbit ==

For maneuvering in orbit, the OV is equipped with three RCS thruster clusters and the two OMS engines. The propellant for these systems is monomethylhydrazine (MMH) oxydized with dinitrogen tetroxide, resulting in a specific impulse of 312 s. This is an hypergolic fuel combination (i.e. ignites automatically). OMS and RCS tanks have an interconnect valve, however only the RCS can be fired from the OMS propellant reserves, not vice versa (currently not modeled).

The OMS engines are located at the rear of the spacecraft in pods attached to the fuselage. Two of the RCS clusters are attached to the OMS pods, one is located at the spacecraft nose.

=== The Orbital Maneuvering System engines ===

The two OMS engines provide a thrust of 6,000 lb and, using the propellant reserves of 7,773 lb of nitrogen tetrozide and 4,718 lb of MMH can induce a total velocity change of about 1000 ft/sec if all propellant is spent. Typically half of this is used to push the OV into a proper orbit after ET separation and for the de-orbit burn, the rest is available for orbital maneuvers such as inclination adjustments.

Once in orbit, in FG throttle control is transferred to both OMS engines. They can be throttled from zero to 100% of nominal thrust and are automatically vectored by the flight controls through the CoG of the orbiter. The real shuttle has a DAP for thrust vectoring of the OMS engines as well as the option of using a single engine with partial thrust vectoring, only the first option is currently modeled.

[[File:OMS_burn.jpg|800px|thumbnail|none|OMS burn for orbital insertion]]
[[File:MS cockpit view Orbit.webp|800px|thumbnail|none|Orbit cockpit configuration]]

=== OMS DAP schemes ===

In orbit, the throttle controls OMS engine thrust. The following DAP schemes are available:

; OMS TVC
: This is a stick-controls-rates scheme which utilizes thrust vectoring for the OMS engines. It resembles in principle the ascent thrust vectoring, except for the fact that the OMS engines are far less powerful and hence rates and the transition to the set rate are a lot slower. Note that this DAP will only control the Shuttle if the OMS is firing.

If TVC for the OMS is not feasible (for instance because the OMS engine gimbal actuators are damaged), the OMS engines can also be fired with an RCS attitude-holding rotational DAP active (for example '''RCS DAP-A'''. In this case, attitude control is provided by the RCS thrusters and thrust by the OMS engines.

=== The Reaction Control System ===

The RCS system consists of three modules, one forward at the nose and two at the OMS pods. The forward module contains 14 primary and 2 secondary thrusters, each aft module carries 12 primary and two secondary thrusters. Propellant reserves in each module are 1,477 lb of oxidizer and 928 lb of MMH. Each primary thruster has 870 lb of thrust with an ISP of 289 s, the secondary Vernier thrusters produce a mere 24 lb each with an ISP of 228 s. Due to geometric constraints, the thrusters are not aligned with the main spacecraft axes or in the same plane (for instance, there is no purely downward firing nose thruster, as its nozzle would have to fire through the heat shield). The layout of the whole system is shown below:

[[File:RCS Jet IDs.gif|600px|Space Shuttle RCS layout]]

Not all thrusters point orthogonal, and not all thrusters have the same nominal thrust - the complete list is as follows

[[File:RCS Break Down Table.gif|600px|List of Space Shuttle RCS thrusters and orientation]]

All of these thrusters are faithfully modeled in FG with their actual orientation and nominal thrust values, including the system of Vernier thrusters, equipping the Space Shuttle with a grand total of 51 distinct engines.

=== RCS DAP schemes ===

The real Space Shuttle has a multitude of (partially mission-specific) DAP schemes, each with different gains and deadbands, which control the thruster firing pattern in response to the controllers. A fair selection of these is implemented in FG. In the real Shuttle cockpit, there is both a rotational hand controller (RHC) and a translational hand controller (THC) to initiate either rotations of the shuttle or translational accelerations (e.g. for approach and docking). In FG, {{Key press|m}} corresponds to switching from THC to RHC to OMS control and back, {{Key press|Shift|m}} switches between the different DAPs and {{Key press|Control|m}} is the override switch to aerodynamical controls. The HUD will display the currently selected mode for clarity.

Due to the geometry of the thruster arrangement, there is significant mode mixing. For instance, a lateral translation firing nose and right pod thruster with the same thrust would also induce a yaw motion (since the modules do not have the same distance to the CoG) and a roll (since they are not in the CoG plane and in fact not even in the same plane). In most implemented modes, the FCS logic takes care of most of these effects by firing additional thruster to cancel the unwanted motion, however in some modes this is not easily possible and mode mixing has to be anticipated and accounted for manually. This is in fact the same as in the real Shuttle.

The Shuttle has four different control pushbuttons (implemented in the menu) to control the basic way the orbital DAP works. These are AUTO, INRTL, LVLH and FREE.

If AUTO is selected, the RCS is controlled by the on-board flight software (specifically either the pointing and tracking routines available on the UNIV PTG display or the automatic burn attitude maneuvering routines available on the MNVR display). In this mode, stick control input is not used. Note that if an automatic maneuver program is selected, the controls need to be switched to AUTO prior to the start of the program. If this is not done, a SEL AUTO warning message is created.

In INRTL (inertial), the stick controls roll rates and the Shuttle holds inertial altitude for stick to neutral. The orbiting Shuttle in this mode thus has an apparent slow attitude drift with respect to the horizon.

In contrast, LVLH (local vertical, local horizon) commands an attitude hold with respect to the local horizon, i.e. the Shuttle appears not to change attitude relative to Earth. Again in this scheme, the stick controls rates.

The following DAPs are available for INRTL and LVLH:

; RCS DAP-A
: A precision 'stick controls rate' scheme in which stick to neutral commands an attitude hold. The mode has fairly strict deadbands and steep gains and hence uses comparatively much propellant to stabilize attitude.

; RCS DAP-B
: As DAP-A, but more permissive in terms of deadbands, trades less strictly stabilized attitude against reduced propellant consumption.

; RCS DAP-A VERNIER
: A 'stick controls rate' scheme in which the Vernier thrusters are used to maneuver the Shuttle. The Verniers are not very powerful and moreover fire in an awkward geometry, so there is significant mode mixing into translations when using them and the response of the Shuttle is very slow - the mode should mainly be used for automatic attitude hold as it is very propellant-friendly.

; RCS TRANS ATT HLD
: A translational DAP in which 'attitude hold' is commanded for all rotation channels. This makes this mode very stable and controllable at the expense of an increased propellant consumption - use e.g. for a precision approach to a docking.

; RCS TRANS LOW-Z ATT HLD
: No upward-firing thrusters are used in this mode to avoid plume impingement on a satellite or docking target. For this reason, forward and backward firing jets are used simultaneously which are both angled slightly upward. For -Z-translations, this causes a 12 times higher fuel consumption. For weak thrust attitude control works well, for strong thrust the controller is, without using upward-pointing thrusters, unable to completely control the pitching motion.

Finally, FREE puts the orbiter into free drift. Stick to neutral then commands all RCS jets off, and stick movements control angular acceleration. The following DAPs are available for this control:

; RCS rotation
: This is a simple scheme in which the stick motion controls thrust, i.e. angular acceleration. Stick to neutral commands no thrust, i.e. the Shuttle will continue its current rotation.

; RCS ROT TAIL ONLY
: A 'stick controls thrust' scheme in which the nose module is not used. This causes significant mode mixing.

; RCS ROT NOSE ONLY
: A 'stick controls thrust' scheme in which the OMS pod modules are not used. This causes significant mode mixing and has very limited roll control (the roll moment only comes from the position difference between left-mounted and right-mounted upward and downward firing thrusters)

; RCS translation
: A translational DAP in which the stick controls translational thrust along the spacecraft x, y and z axes. Stick to idle commands no thrust, but the Shuttle will of course retain its relative velocity to a fix point until counter-thrust is used. RCS translation can be used for emergency de-orbit burns if the OMS is not available. Limited compensation is done for cross-coupling to rotational modes.

; RCS TRANS LOW-Z
: To prevent thruster plume impingement on a docking target, say the ISS, in this mode all upward-firing thrusters are inhibited. To provide the deceleration force for a docking (which is needed in -Z direction), foreward and backward firing thrusters are used simultaneously - since they point about 10 degrees upward, this provides a downward acceleration without upward plume at the expense of 12 times higher than normal propellant consumption. There is strong cross-coupling to a pitching motion.

The following DAPs are available for re-entry (OPS 304):

; RCS ROT ENTRY
: A 'stick controls rates' DAP designed for entering the atmosphere which enforces a 'no sideslip' attitude in which the nose module is not used. This has very strict deadbands and aggressive gains to combat the yaw instability of the Shuttle upon entry, significant mode mixing and is very propellant-consuming. Do not use in orbit and only activate at the entry interface once the shuttle has the correct attitude! During entry, the DAP will gradually transfer control to the 'Aerodynamical' DAP - at qbar of 10 lb/sqft the roll axis, at 40 lb/sqft the pitch axis and at around Mach 3.5 the yaw axis.

; Aerojet
: The Aerojet DAP is close to the real entry DAP used by the Shuttle. Its RCS part works similar to RCS ROT ENTRY, but control is not transferred to to the Aerodynamical DAP but to the atmosphere part of Aerojet (see below) which employs the same rate control routines as the RCS part. The scheme also supports an automatic AoA control scheme in which the pilot only has to manage the roll axis during entry, which makes this the most easy to fly DAP for entry and atmospheric flight.

For precision control, the keyboard is a more suitable input device than a joystick or a mouse since exact nulling of rates is somewhat easier with keystrokes.

==== Orbital DAP configuration ====

As of November 2015, the Shuttle's orbital DAPs are configurable using the SPEC 20 utility. This allows to set characteristics such as the roll rates achieved for a given controller movement, deadbands for attitude and rate holding as well as to switch the nose / aft RCS pods selectively off to conserve propellant.

[[File:Dap_config_spec_20.jpg|600px|thumb|none|DAP utility display of the Space Shuttle]]

Note that the DAP characteristics configuration allows to specify unstable or ineffective use of the RCS, thus changes should be entered with care.

==== Key mapping for RCS rotation DAP ====

{| class="keytable"
! Key
! Function
|-
|{{Key press|4}}
|Roll left
|-
|{{Key press|6}}
|Roll right
|-
|{{Key press|2}}
|Pitch up
|-
|{{Key press|8}}
|Pitch down
|-
|{{Key press|[}}
|Yaw left
|-
|{{Key press|]}}
|Yaw right
|-
|{{Key press|5}}
|Cut thrust
|}

==== Key mapping for RCS translation DAP ====

{| class="keytable"
! Key
! Function
|-
|{{Key press|4}}
|Left
|-
|{{Key press|6}}
|Right
|-
|{{Key press|2}}
|Down
|-
|{{Key press|8}}
|Up
|-
|{{Key press|[}}
|Backward
|-
|{{Key press|]}}
|Forward
|-
|{{Key press|5}}
|Cut thrust
|}
.

=== Spacewalk ===

The Shuttle version as of May 2015 contains a 'proof of concept' spacewalk view designated 'EVA'. This is intended to simulate the view of an astronaut using a MMU. In the EVA view, use {{Key press|Shift|E}} to initiate spacewalk. The stick then controls the MMU thrusters and {{Key press|m}} is used to switch between the translational and rotational modes of the MMU.

Before spacewalk is initiated, the yaw, pitch and roll rates of the Shuttle need to be nulled (since control inputs during spacewalk refer to the MMU, the Shuttle also can't be controlled from this view).

Once outside, the MMU can be used to float around the Shuttle, or to inspect co-orbiting objects. However, note that it is impossible to leave the EVA view unless the astronaut maneuvers back to the airlock. Currently it is not possible to see spacewalk from outside, nor can the view direction be adjusted - in a future implementation, spacewalk will be improved using the FG walker functionality.

== Aerodynamics of the Space Shuttle Orbiter ==

The conditions encountered by the Space Shuttle span a wide range from a thin, rarefied atmosphere at Mach 27 to a sea level atmosphere flown at about Mach 0.6. Over this range of conditions, the handling characteristics change quite dramatically.

Somewhat simplified, one can divide the atmospheric entry in three phases - an initial near-ballistic entry phase in which airfoils are essentially useless, an aerodynamical entry phase in which the Shuttle is controlled by airfoils and aerodynamical forces are very noticeable on the trajectory, but in which the flight dynamics is completely different from that of an airplane and the final approach and landing phase during which the Shuttle is flown like an aircraft.

[[File:Shuttle-landing04.jpg|800px|thumbnail|none|Early near-ballistic entry phase]] 
 
[[File:Glowing red 2.jpg|800px]]

During these phases, control is passed from RCS jets to the airfoils - the inboard and outboard elevons at the trailing wing edges and the rudder/speedbrake at the tail stabilizer fin. The elevons can be deflected from -40 to 25 degrees, the rudder from -25 to +25 degrees. At a qbar of 10 lb/sqf roll control is taken over by the airfoils, at 40 lb/sqf pitch control is managed by airfoils and below Mach 3.5 finally yaw control is transferred, at which point the airplane-like phase of the entry starts. In addition to the primary airfoils, the Shuttle is equipped with a body flap which can be used to adjust trim.

During the first two phases, the Shuttle is flown with a high AoA (initially 40 degrees) to create a detatched bow shockwave which keeps the heat of atmospheric entry away from the fuselage. The characteristic hallmark of this attitude is that the stabilizer fin is shadowed by the wings - this renders the rudder ineffective above Mach 6 and makes the Shuttle yaw unstable against sideslip above Mach 2, i.e. any sideslip must be very accurately controlled by the FCS during entry or the Shuttle will tumble uncontrolled. This can not be done by the rudder, thus yaw jets remain crucial for controlling the Shuttle down to Mach 3.5.

Another effect is that the elevons deflected upward are in the lee of the wings, significantly reducing their effectivity as compared to downward deflections. However, in the entry regime, operating the elevons upward is more advantageous due to heating constraints.

=== Lift / Drag ===

Despite being designed for a gliding approach and landing, the Shuttle is not actually a very good glider - even close to approach, the glide ratio (i.e. L/D) reaches about 4.5, much less than most normal planes would have.

[[File:L-D-mach.gif|‎500px|thumbnail|none|Lift to drag as a function of AoA for different Mach numbers]]

The maximum of L/D varies somewhat with Mach number, however for hypersonic flight thermal constraints force a high AoA and aerodynamical efficiency is a secondary concern. Only in the supersonic to subsonic phase is the Shuttle flown close to its optimum glide ratio.

Due to the Delta-wing design, L/D has no pronounced stall even at high AoA in any region. However, the need to have sufficient lift despite the relatively poor aerodynamics forces a high touchdown speed of about 200 kt.

=== Longitudinal Dynamics ===

In the near-ballistic entry phase, pitch is controlled by an attitude-hold mode of the RCS, however elevons are automatically trimmed by the FCS to negative (upward) deflections to take some of the load early on to conserve propellant.

The pitching moment induced by the control surface varies dramatically as function of Mach number.

[[File:Control response.gif|500px|thumbnail|none|Pitching CM moment]]

As seen from the figure, at high Mach numbers the response is fairly flat (i.e. large elevon deflections are needed to control the Shuttle) and also non-linear (upward deflections cause much less pitching moment than downward deflection). In contrast, at low Mach numbers small elevon deflections already cause large moments and the response is almost linear. In all regimes, the pitching moment is normal force (i.e. AoA) dependent.

Since the elevons supply both pitching and roll control, at high hypersonic Mach numbers roll controls are close to being saturated with elevons deflected near full up. To open up better roll control, below Mach 10 the speedbrake is opened to provide a pitching moment relieving the elevons, and the Shuttle's body flap can also be trimmed upward.

=== Lateral stability ===

As mentioned above, during most of the entry phase, the Space Shuttle has no rudder action and the yawing moment as a function of sideslip angle beta is negative, indicating instability. This means that the FCS has to manage yaw stability by commanding yaw thrusters to maintain near zero beta, which is increasingly more challenging as the Shuttle penetrates deeper into the atmosphere and aerodynamical forces grow while thrust is reduced as compared to nominal vacuum values. This implies that a sizable amount of RCS propellant (about 1/3 of the capacity to be on the safe side) needs to be available before atmospheric entry.

Below approximately Mach 6, the rudder starts to contribute to yaw stability and from Mach 3.5 down to Mach 2 where the yawing moment finally becomes positive only the rudder is used. The roll behavior of the orbiter before any FCS is somewhat skittish as the roll moment as a function of roll rate is not a large damping term over most of the Mach range. The FCS of the Shuttle in FG therefore does not place yaw and roll axis directly under pilot control. The rudder is always commanded to minimize beta and no pilot input for the rudder should be needed or used unless sideslip is explicitly desired. The elevons are commanded to provide a simple roll damper to make control smoother.

The real Shuttle has in addition a '''NO Y JET''' mode to stabilize the orbiter during entry in which the elevons are used to control yaw. This leads to significantly reduced roll control since roll then needs to be driven by adverse yaw till the rudder picks up sufficient airflow. This mode has been implemented since dev version of july 2017.

=== A note on thruster efficiency in the atmosphere ===

Thrusters used in the hypersonic rarefied airflow of the upper atmosphere do not only cause the yaw, pitch and roll moment by the thrust acting at a certain distance to the CoG, but also are subject to plume impingement on the orbiter fuselage and interactions with the air flow field.

While impingement generically degrades the effectivity, the interaction moment can somewhat counter-intuitively act both directions. In particular the yaw moment is increased by the airflow, helping to stabilize the Shuttle.

As of May 2015, none of these effects is modeled in Flightgear.

=== Control cross couplings ===

The Shuttle has significant cross couplings between the elevon deflection in pitch and roll mode and the rudder as a function of Mach number, all of which are faithfully modeled in FG. One of the main effects is that upward elevon deflection alters the airflow at the aft fuselage, creating additional suction effects which alter aerodynamical forces.

In particular, at supersonic speeds yaw stability is somewhat improved at high upward elevon deflection while the effect reverses at subsonic speeds. At the same time, roll control is significantly reduced at full elevon deflection, with the effect being more pronounced at low than at high Mach numbers.

Control surface effectiveness in general drops with increasing Mach number, however the speed at which this happens is different for elevons and rudder.

=== Aerodynamical DAP schemes ===

There are two different control schemes available for the aerodynamical part of the Shuttle's flight - one of them based on the real Shuttle DAP, the other educational.

; Aerojet
: The Aerojet DAP is closest to what the real Shuttle uses. It is a scheme in which the stick commands pitch and roll rates and stick in neutral position commands attitude hold. Above Mach 3.5, in addition an automatic pitch control mode can be activated which maintains the scheduled safe entry AoA. Flying the Shuttle is very easy in this mode - there is no operational need to use trim or rudder and response to control input is crisp and precise. During entry, Aerojet can manage even agressive roll reversals inside the stable region.

; Aerodynamical
: This is an educational mode in which the Shuttle is flown similar to an airplane, i.e. the stick basically controls the airfoil positions, and in order to achieve level flight with stick neutral, trim has to be used. Since the Shuttle is yaw-unstable at high Mach numbers, this mode still has automatic stability augmentation, i.e. rudder and ailerons are commanded automatically to minimize sideslip. Entry can be flown with this mode starting in-orbit with '''RCS ROT ENTRY''' and illustrates the amount of work the rate controller has to do as well as gives a hands-on feeling for hypersonic aerodynamics. This however is somewhat challenging and it is possible to maneuver the Shuttle outside its stability envelope using too agressive maneuvers. Once below Mach 5, the Shuttle responds well and stable to direct aerodynamical control.

=== Entry and touchdown structural and aerodynamical limits ===

The following structural and aerodynamical limits need to be observed during entry and landing:

* Dynamical pressure qbar < 375 lb/sqf (modeled)

This is a structural limit for the orbiter and the airfoils, beyond this the actuators can no longer move the airfoils, leading to a loss of control. In nominal operations the orbiter should be kept below 250 lb/sqf.

* Peak temperature < 2900 F (modeled)

This is the approximate limit beyond which the thermal protection system fails, with subsequent structural failure of the overheated airframe and loss of the orbiter.

* gear extension speed < 312 KEAS (modeled)

Structural limit of the gear against aerodynamical forces.

* vertical speed upon touchdown < 9 ft/sec (modeled)

This is the structural limit of the main gear struts, and their destruction is fully modeled in 'realistic' mode.

* airspeed upon drag chute deployment < 230 kt (modeled)

The drag chute has a safety pin which disconnects the chute if the airspeed is higher than the stability limit. This is fully modeled.

* roll speed of tires < 230 kt (not modeled)

This is the certified maximal speed at which the tires don't blow.

* derotation speed < 2 deg/s (modeled)

This is the structural limit for the nose gear strut, and nose gear breakage is fully modeled.

* AoA < 15 deg on touchdown (modeled)

Beyond this angle, the body flap and tail structure of the orbiter touch the ground before the main gear does.

[[File:Fin.jpg|800px|thumbnail|none|Touchdown and drag chute deployed]]

== Systems ==

Most of the Shuttle's systems are designed around the philosophy that failure of any one component should allow the mission to continue and failure of two components should still allow a safe return to Earth. As a result, most systems exist triple, and the loss of one subsystem is not normally felt when operating the Shuttle, only a loss of two subsystems requires to take special action and compromises the maneuverability of the vehicle.

In the real Shuttle, many system switches have a 'GPC' (general purpose computer) setting in which the computer controls a system automatically and an 'on' setting in which the system is manually controlled. In FG, the system control is a bit simplified as no GPC or mission control is simulated and not all existing sensor readings are simulated which would be necessary for manual control. Often 'GPC' and 'on' are merged into one setting for which, dependent on system, either the user has to always control a system manually or a control routine is activated and no manual control is possible.

=== Electric Power Generation ===

Electricity aboard the Shuttle is generated by three fuel cells (FCs) which produce electricity utilizing the reaction of cryogenic hydrogen and oxygen into water (which is then used in the environment system). Each fuel cell can supply about 12 kW of power, which means plenty of redundancy given the normal power consumption of the orbiter is about 14 kW.

The fuel cells normally circulate hydrogen and oxygen in a closed loop to avoid losses, however they have to be periodically purged (reaction products vented into space) to avoid their effectivity to decrease by contamination.

As of June 2015, the power generation as well as the coarse power balance of the orbiter is modeled (i.e. switching components on which use electricity will have to be supplied by the running FCs), however not all the details of the electrical distribution system or the reactant feed lines are done. In normal operation, the electrical power system should require very little crew intervention.

=== Auxiliary Power Unit and Hydraulics System ===

Thrust vector control of the SSMEs during ascent, movement of the various aerosurfaces, deployment of the landing gear and brakes/nose wheel steering all rely on hydraulic pressure to operate.

The Space Shuttle is equipped with three independent hydraulics systems, each of them powered by an Auxiliary Power Unit (APU), a turbine utilizing hydrazine as propellant. Under normal load conditions, each APU utilized about 3 - 3.5 lb of propellant per minute. With a hydrazine load of 332 lb, this means the system can be operated for about 90 minutes under nominal conditions or be run in a power-saving mode for 110 minutes during an once around abort. This means that the APUs have to be switched off when not used - they are powered down as part of the post-MECO operations and powered up as part of the atmospheric entry preparations.

As compared to the rest of the Shuttle's systems, the APU turbines with with 180 kW power each generate a lot of waste heat which ends up warming the hydraulic fluid and the lube oil. The APUs are operated at a temperature of over 390 K (250 F) though, so for an APU cold start it takes a bit more than 10 minutes to reach that temperature. Afterwards, the water spray boiler systems have to be used to cool hydraulic fluid and lube oil - they are supplied by three water tanks containing 142 lb of water each and can spray up to 10 lb / minute for cooling purpose. Overheating APUs can not be run for more than 2-3 minutes before they fail.

When not in use, electrically powered hydraulic circulation pumps keep the hydraulic fluid moving such as to equalize temperatures in the components.

In case of a hydraulic failure, Priority Rate Limiting (PRL) for the airfoils is used to allocate the remaining power as efficiently as possible. Usually the elevons move with 20 deg/s and the rudder with 14 deg/s, however in the case of multiple hydraulic failures, these numbers are reduced to 13.9 deg/s for elevons and 7 deg/s for the rudder. The orbiter is still fully controllable in this case, but not as responsive to agressive maneuvers.

As of June 2015, the APU and hydraulic system is modeled with a fair amount of detail and operated from a dedicated menu. APUs need to be started as part of the pre-launch checklist - refer to Help/Aircraft Checklists for the detailed procedure. '''If the hydraulic system is not available during ascent, this will result in loss of the vehicle after SRB separation as there is no control over the Shuttle if the SSMEs can not be gimbaled.''' Also PRL for all airfoils is fully supported.

Operation of the water spray boilers is realistically integrated into the heat transfer model of the Shuttle (see below), including the failure of overheating APUs.

=== Active Thermal Control System ===

In orbit, the Shuttle's systems use on average about 14 kW of power, which eventually ends up heating the interior of the pressure vessel. Active cooling systems carry the heat load away and radiate it into space. A water coolant loop system takes care of the avionics bays and the cabin and exchanges heat with a two loop freon coolant system which also cools systems elsewhere in the Shuttle. The freon is circulated through the radiator panels located on the inside of the payload bay doors and dumps a maximum of about 18.000 W of heat into space.

If the payload bay doors are closed (such as during ascent or entry), the freon loop can be cooled by flash evaporators which utilize quickly evaporating water sprayed on the freon tubes as coolant. To provide the cooling performance of the radiator, this system uses about 66 lb of water per hour, i.e. can only be a temporary measure as the water storage aboard would be quickly depleted otherwise.

The heat balance in space is also influenced by the orientation of the Shuttle relative to the Sun and Earth - sunward facing surfaces tend to heat up to 350 K whereas shaded surfaces may cool down to 150 K. To ensure ice-free thruster and other exhausts, electrical heating elements may therefore be needed.

Orbiter heat management often combines cooling systems and attitude - for instance placing the OV into a tail to Sun inertial attitude minimizes incident heat and allows to cool the freon down so that it can act as a heat sink for about 15 minutes even without the radiator deployed, a technique known as 'cold soak'. Similarly, orienting the payload bay towards Earth ensures that even during the night, temperatures don't drop too much so that EVA work is possible. Temperatures can be equalized across the Shuttle by slowly rotating the spacecraft.

As of June 2015, the FG Shuttle includes a fairly sophisticated simulation of the heat balance, including incident heat flux from Sun and Earth dependent on surface normal and albedo, internally generated heat in the avionics bays, heat transport via conduction and via the cooling loops, radiated heat from the surfaces the action of the flash evaporators and the radiator. Most real heat-management techniques, including cold soak and slow rotations, are fully supported.

[[File:Shuttle coldsoak.jpg|600px|thumbnail|none|Cold-soaking the Shuttle's freon loops in preparation for de-orbit.]]

Thermal inertia of the Orbiter is generically high - temperatures adjust at timescales of hours rather than minutes to their equilibrium values. For educational purposes, it is possible to choose simulation options which speed up the approach to thermal equilibrium by a factor or 10 or 100 respectively - this will result in an almost immediate response of the temperature distribution to e.g. changes in attitude. These options should be used with care.

=== Main Propulsion System ===

Under the name Main Propulsion System (MPS), the various subsystems operating the SSMEs are summarized. This includes the SSME controllers (two per engine for redundancy), the propellant feeding system supplying liquid hydrogen and oxygen to the engines and the various hydraulically operated valves, a helium system to supply purge gas flows and emergency hydraulics power and finally the engines themselves.

The SSME's feed high-pressure propellants into the combustion chamber. Power for the turbo pumps is provided by partial pre-combustion of the propellant, and ullage pressure in the external tank is maintained by branching off a small fraction of vaporized propellant back into the tank. The precise opening of the propellant feeding valves which throttles the engines is governed by the controllers which in turn receive throttle commands from the Shuttle's guidance computers.

For the most part, the MPS settings are controlled on the ground prior to launch and not changed during ascent, however after MECO there are about 5,200 lb of propellant trapped in the feeding manifolds which need to be dumped. During this propellant dump, high-pressure helium is used to vent liquid oxygen through the thruster exhausts while hydrogen is allowed to boil off through the fill/drain valves.

In case of a hydraulic failure, the SSMEs can neither be gimbaled nor can their valves be changed. Each of the three hydraulic systems operated the valves of one engine, and each engine gimbal is supported by two hydraulic systems (i.e. it takes two failures to disable gimbal on one engine, but each hydraulic failure will disable valves on one engine).

If the valve settings can no longer be changed, the engine can still continue to run, but it can't be throttled any more, a condition known as 'hydraulic lockup'. It is still possible to shut down such an engine using pressure from the helium system though. Similarly, if sensors monitoring combustion chamber conditions or the command path from guidance computer to engine controllers fail, the engine is in a condition called 'electric lockup' - the controller will continue to operate it with the last known settings. Locked-up engines usually need to be shut down manually using the cutoff switches about 30 seconds prior to nominal MECO.

As of June 2015, the MPS is modeled in a good amount of detail, including most of the relevant valve settings, hydraulic and electric lockup, power failures on the engine controllers and the propellant dump sequence. The in-sim checklists provide instructions on how to execute the propellant dump and how to safe the engines for orbital operations.

=== Mechanical Systems ===

The Shuttle uses electromechanical actuators to move components which do not require hydraulic power. This includes the ET umbilical doors and the payload bay door. Each actuator contains two separate motors for redundancy, and transition time for any motion doubles if a motor is non-functional. The movement of these components is not time-critical, and hence usually slow - the complete payload bay door opening sequence takes about four minutes at normal speed to execute, twice that for actuator failures.

The ET umbilical doors are open at launch to allow the oxidizer and fuel feedlines to enter the orbiter, and they need to be closed after reaching orbit for the thermal protection during entry to be efficient. The payload bay doors are closed during ascent and entry and only opened in orbit. This is crucial, as the freon cooling loop radiators are located on the inside of the payload bay doors, i.e. the Shuttle can not remain indefinitely in orbit without opening the payload bay.

Opening or closing mechanical components usually involves unlatching, moving and possibly re-latching the components.

As of June 2015, the normal operation of ET umbilical door and payload bay door is implemented, but no actuator failures. The sequences can be driven from the GUI in automatic mode, but there is in principle support to drive them in manual mode as well as described in the Shuttle Crew Operations Manual.

Note that there's cross talk between mechanical systems and thermal modeling - tension building in the Shuttle due to uneven heating of the left and right fuselage can prevent the payload bay doors from opening or closing for instance.

== Guidance systems ==

=== Automated flight ===

Automated flight is available for all nominal mission phases except for the final approach and touchdown (for which in reality no AP is available either) as well as all single engine loss intact ascent aborts and all two engine out contingency aborts ending in either emergency landing or crew bailout.

Unlike an airplane which is usually in or close to a steady-state equilibrium (level flight at cruise altitude) when under AP control, this is almost never the case for the Shuttle. Thus, the AP requires a context to work properly - whether a current state vector is good or bad depends on what one wants to achieve. Usually this context is a guidance target (i.e. a desired orbit, a landing site, an abort MECO condition,...) and if no such target is provided, the AP will not engage.

If there is a valid guidance target, the PFD will display error needles even if the AP is disengaged which reflect what the AP would try to do in the current situation which can be used for manual piloting. The AP can be used separately in the pitch and yaw/roll axis and independently for throttle/speedbrake control.

Once disengaged, it is as a rule not wise to re-engage the AP if the Shuttle has deviated too much from the intended state. Many AP stages are based on closed loop guidance and will try to steer back to the desired solution, however this may not be possible.

Also, automated flight does not mean the pilot can lean back and the Shuttle will handle all aborts on its own - some AP modes specifically need to be engaged or augmented by DPS options to properly work - see the Crew Operations Manual for detailed instructions. In particular, if in an emergency the wrong AP mode is engaged, the Shuttle may try to solve a kinematically impossible maneuver which usually results in loss of control.

Finally, do not expect miracles from the AP. It will usually save the orbiter even after the loss of two engines, but it may not always on its own find a viable solution to a landing site in an abort scenario. In general, automated flight is much better at manging the instantaneous state (holding an alpha schedule, aiming at a waypoint) than at longer-term planning (managing gliding range after an abort,...).

Different from the powered and gliding phase, the orbital DAP contains automatic routines for attitude management - pointing the Shuttle, tracking a location or a celestial object or automated OMS burn maneuvers.

Operating the Shuttle AP properly is very different from operating airplane APs and requires a profound knowledge of OPS sequences and major mode transitions as well as strict adherence to the published procedures.

=== Ascent guidance Powered Explicit Guidance (PEG) ===

{{note|Full explanations about the Ascent guidance might be found there: [[Shuttle guidance - Ascent guidance Powered Explicit Guidance (PEG)]]}}

The purpose of this section is to present and discuss about the second stage ascent guidance (post SRB sep) for Nominal Orbital Insertion, and some Intact Aborts (TAL / AOA / ATO).
The guidance is based on the real closed loop used in the Shuttle, known as Power Explicit Guidance https://www.orbiterwiki.org/wiki/Powered_Explicit_Guidance.

'''Documentations'''

*A very detailled and complete topic about the guidance by Noiredd who implemented it in Matlab and KSP: https://github.com/Noiredd/PEGAS-MATLAB/blob/master/docs/upfg.md
*A deeper document with nice schematic drawings: Ascent Guidance Navigation and Control Shuttle Workbook (page 111) https://www.google.com/search?client=firefox-b-d&q=ascent+guidance+workbook+shuttle
*Original formulation of the Unified Power Explicit Guidance with equations and algorithms: ''ntrs.nasa.gov/citations/19740004402''
*A paper about enhancements made over the years to the original ascent guidance: ''ntrs.nasa.gov/citations/20180002035''

'''Overview'''

Second stage guidance functions very differently from first stage guidance in that second stage guidance is closed loop. Second stage guidance computes the control variables (essentially commanded attitude and attitude rates) and burn time to go (TGO) in such a way that the vehicle flies from the current state to the prescribed target conditions (altitude, velocity, flight path angle, and orbit plane) within trajectory constraints. It solves this two point boundary value problem each cycle (every 1.92 seconds). One limitation of second stage guidance is that it doesn't calculate if there is enough propellant to reach the desired MECO conditions.
[[File:PEG Meco target.webp|400px|thumbnail|none]]

The powered explicit guidance (PEG) scheme used by second stage guidance nominally operates in two phases. The first phase computes throttle and attitude commands based on three SSMEs and a constant thrust requirement until an acceleration of 3g is reached. At that time, the second phase, which uses variable throttle to maintain a constant acceleration, is entered. If an engine failure is detected, a third phase of PEG, which computes the necessary guidance commands using constant thrust to aim for the desired targets using two SSMEs, is entered (assuming no RTLS or TAL abort).

During current shuttle operations, only two phases of PEG are used, constant thrust through 3g and then variable thrust through main engine cutoff (MECO). STS-1 and STS-26, in order to prevent or reduce abort gaps, flew higher than normal trajectories, called lofted or abort shaped. This method required the third PEG phase, which ran from SRB sep to T_FAIL (I-loaded MET) and achieved lofting by assuming that an engine would fail causing loss of performance at the time T_FAIL. When T_FAIL occurred, PEG stopped assuming that an engine would fail. A drawback with this method was discovered later, however. The lofted trajectories caused “black zones,” or regions where an unsurvivable entry/pullout condition would be created if two engines actually did fail (CA). For this reason and the fact that abort shaping costs thousands of pounds of nominal ascent performance (payload), the I-load, T_FAIL is now set to zero, and lofted trajectories are not currently planned.
[[File:PEG step.webp|600px|thumbnail|none]]

Second stage guidance performs yaw steering to achieve the desired orbit plane. The desired orbit plane is defined by the unitized negative angular momentum vector (I-loads), commonly referred to as the '''IY vector'''. The x and y components of the IY vector define the nodal crossing, while the z component defines the inclination. For missions which do not involve rendezvous with a vehicle already in orbit (referred to as the “target”), the IYs are defined during the flight design process approximately 6 months prior to launch. These missions employ “earth fixed” yaw steering since the trajectory relative to the earth remains the same regardless of launch time. In order to successfully launch into orbit and rendezvous with another vehicle already in space, the orbiter must end up in the same orbital plane and altitude as the other vehicle.
[[File:PEG insertion.webp|600px|thumbnail|none]]

Forty seconds prior to MECO, guidance no longer seeks to achieve the altitude and orbital plane position targets. Common terminology is, “at MECO minus 40 seconds, the position constraints are released.” Without this constraint release, when TGO becomes small, a small change in position error would produce large changes in the thrust turning rate vector and over controlling would result. Note also that the cutoff time (TGO) calculation includes the predicted velocity change from the time minimum throttle is commanded to burnout. This corresponds to the predicted tailoff impulse from each active SSME and is known as fine count. Fine count occurs 10 seconds prior to MECO for nominal ascent, ATO, and TAL and 6 seconds prior to powered pitchdown for RTLS. It is at fine count where second stage, closed loop guidance is terminated and the SSMEs are commanded to a lower power level, usually 67% for three engines running or 91% for one or two engines running (note that the SSMEs aren't throttled back until powered pitchdown during an RTLS). Thereafter, the flight path angle constraint is released, such that TGO is computed solely on the desired velocity change (VGO). When guidance sees the shuttle at the correct inertial velocity (VI), all SSMEs are commanded to shut down.

=== Entry guidance algorithm ===

{{note|Full explanations about Entry shuttle guidance might be found there: [[Shuttle guidance - Entry guidance algorithm]]}}

A topic speaking about the entry guidance algorithm.

'''Documentations'''

I didnt use hyperlinks to avoid NASA ntrs server spam from forum robots

*A quick overview of the Descent guidance from the Space Shuttle Technical Conference: ''ntrs.nasa.gov/citations/19850008593''
*A deeper look into the Entry equations formalism with that paper that you might find under: ''Shuttle Entry Guidance JSC-14694 ''
*Entry guidance formulation requirements (code): ''ntrs.nasa.gov/citations/19800016873''

All the documentations linked in the Entry/TAEM rework are even more useful now, as almost all the parts of Entry guidance are simulated and displayed parameters fed with consistent datas.
https://forum.flightgear.org/viewtopic.php?f=87&t=38777

=== TAEM/Approach guidance algorithm ===

{{note|Full explanations about Entry shuttle guidance might be found there: [[Shuttle guidance - TAEM/Approach and Autoland guidance]]}}

== Avionics and DPS ==

The avionics of the Space Shuttle is fairly faithfully reproduced by the simulation, see the dedicated article on [[Space Shuttle Avionics]] for an overview. The implemented screens include routines to monitor the various systems as well as guidance navigation and control for all mission stages.

[[File:GNC_sys_summ_up_2.jpg|600px|thumbnail|none|GNC SYS SUMM 2 display of the Space Shuttle]]

All nine MDUs of the forward panel are usable and display the DPS and MEDS screens of the Shuttle - this includes launch and entry guidance routines, TAEM guidancs as well as orbital tracking and pointing management. In addition, HUDs for Commander and Pilot are provided.

[[File:Shuttle_cockpit_OPS_2_day.jpg|1000px|thumbnail|none|Space Shuttle cockpit Day]] [[File:Shuttle_cockpit_before_launch.jpg|1000px|thumbnail|none|Space Shuttle cockpit Night]]

An alternative display for all phases of flight is provided by the FG-native the HUD. This has four different modes - ascent, orbit, entry and approach, and dependent on the HUD mode, different information relevant for the mission phase is displayed. In all cases, the current CSS DAP is identified in the upper left.

There is a calculator for orbital elements available, determining perigee and apogee, orbital inclination and longitude of the ascending node (the latter is currently not so useful as it is obtained in an inertial coordinate system). Based on these orbital elements, the groundtrack map displays current position of the Space Shuttle, selected landing site, ground track history and a prediction of the future orbit - if the perigee is below the surface of Earth, the prediction ends at the estimated ballistic impact point (note that due to the aerodynamical capabilities of the Shuttle, the actual landing site can be within a cross range of about 1000 miles around that point dependent on how the trajectory is managed during the entry phase).

== Payload handling ==

The Space Shuttle is equipped with the capability to release payload from the bay into space, or to catch a payload from space and deposit and secure it in the bay. For this, the Remote Manipulator System (RMS) arm in combination with the payload retention system is used.

[[File:Hubble docked.jpg|600px|thumbnail|none|Handling a payload with the RMS arm]]
[[File:Hubble COAS.jpg|600px|thumbnail|none|Hubble through COAS system]]
[[File:Hubble_grapple.png|600px|thumbnail|none|Handling Hubble with the RMS arm]]

=== RMS arm operation ===

The RMS arm is a fairly complicated device with six different joints, each allowing rotation along one specific axis, which is formed after the human arm. The nomenclature is borrowed from this analogy, so there is a shoulder yaw, a shoulder pitch, an elbow pitch, a wrist pitch and wrist yaw and roll joints. Each of the joints can only be moved a certain angular range. At the end of the RMS arm is the end effector which is the device which can attach to a payload.

The RMS arm can be driven in various modes. The simplest of these are the single joint or the direct mode in which each joint angle is controlled separately, i.e. the arm is extended by first selecting a joint, then commanding it to either increase or decrease angle, before the next joint is selected.

Since this is cumbersome, the more natural control modes allow to use the stick (or whatever control device is attached) to directly move a reference point. In the ORB UL x/y/z mode (UL stands for 'unloaded') the reference point is the tip of the end effector, i.e. using the stick just moves the joint angles such that the end effector moves along the x, y, or z-axis and otherwise keeps its attitude. The ORB UL yaw/pitch/roll mode in contrast keeps the end effector's position and just changes its attitude.

The real Shuttle has additional modes in which the reference point is in the center of the payload, or in which the reference coordinate system is changed from the Shuttle's coordinate system to a system co-moving with the end effector camera - these are as of August 2015 not implemented in FG.

All modes except single and direct joint driving have software safety stops when the joints approach their limit extensions. Since in its stowed position, two of the joints are in the software stop region, it is necessary to directly drive shoulder pitch and elbow pitch out of their soft stop region to be able to use the more sophisticated control modes - see the diagram below for the reach angles of each joint.

[[File:Joints.gif|600px|thumbnail|none|RMS arm reference coordinate system and joint reach angles]]

Finally, the RMS arm is secured by a shoulder brace to make it cope with launch acceleration. This brace needs to be removed before the arm can be operated, and the arm itself needs to be powered, deployed and unlatched.

=== Payload retention system ===

The payload retention system is a series of latches which hold a payload in the bay. Before a payload can be lifted out of the bay, these latches need to be released. Similarly, if a payload is returned into the bay, ready-to-latch indicators show when it has reached the correct stowing position and it can only be safely released from the RMS arm once the latches are closed.

The real Shuttle has three different payload positions with corresponding latch controls, as of August 2015 only one payload position is supported in FG. Likewise, currently only a simple demo satellite with no proper folding/unfolding animation is available as visual payload (note that a payload mass affecting the FDM can also be chosen in the 'Fuel and Payload' dropdown menu).

== Mission phases ==

The various phases of a Shuttle mission are generically subdivided into launch, orbit, entry, TAEM and approach. These can directly be accessed by appending the mission phase to the command line. This will automatically start the Shuttle in the correct configuration and the correct state for the mission selected. For instance, --aircraft=SpaceShuttle-TAEM --airport=KVBG will initialize a TAEM approach into Vandenberg, --aircraft=SpaceShuttle-orbit --lat=30.0 --lon=0.0 --heading=90.0 will initialize the Shuttle in a 30 deg inclination orbit.

Note that --aircraft=SpaceShuttle-entry combined with an airport as location will ''not'' initialize you on an entry trajectory to that airport since the entry interface is several thousand miles away from the landing site and moreover the trajectory needed is not unique but depends on what you fly - you need to initialize the entry interface location by hand using latitude and longitude.

Specific information on the mission phases can be found in the following articles:

=== Documentations ===

[[Flying the Shuttle - Space Shuttle Checklists]]

=== Nominal Operations ===

[[Flying the Shuttle - Launch]]

[[Flying the Shuttle - Orbital Operations]]

[[Flying the Shuttle - Entry]]

[[Flying the Shuttle - Final Approach]]

=== Nominal Operations Advanced Tutorial ===

[[Flying the Shuttle - Launch And Post Insertion Advanced]]

[[Flying the Shuttle - Deorbit Preparation Advanced]]

[[Flying the Shuttle - Deorbit Burn and Final Entry Preparation Advanced]]

[[Flying the Shuttle - Entry TAEM and Landing Advanced]]

=== Intact Aborts ===

[[Flying the Shuttle - Intact Abort Procedures Overview]]

[[Flying the Shuttle - Return To Launch Site RTLS]]

[[Flying the Shuttle - Transoceanic Abort Landing TAL]]

== Glossary of acronyms ==
{|
| '''AoA''' || Angle of Attack
|-
| '''APU''' || Auxiliary Power Unit
|-
| '''CoG''' || Center of Gravity
|-
| '''CSS''' || Control stick steering
|-
| '''DAP''' || Digital autopilot
|-
| '''ET''' || External tank
|-
| '''EVA''' || Extravehicular Activity (spacewalk)
|-
| '''FC''' || Fuel cell
|-
| '''FCS''' || Flight Control System
|-
| '''ISP''' || Specific impulse
|-
| '''MECO''' || Main Engine Cutoff
|-
| '''MMH''' || monomethylhydrazine (a propellant)
|-
| '''MMU''' || Manned Maneuvering Unit
|-
| '''MPS''' || Main Propulsion System
|-
| '''OV''' || Orbiter vehicle
|-
| '''OMS''' || Orbital Maneuvering System
|-
| '''PRL''' || Priority Rate Limiting
|-
| '''RCS''' || Reaction Control System
|-
| '''RHC''' || Rotational Hand Controller
|-
| '''RMS''' || Remote Manipulator System
|-
| '''SRB''' || Solid rocket booster
|-
| '''SSME''' || Space Shuttle main engine
|-
| '''TAEM''' || Terminal Area Energy Management
|-
| '''THC''' || Translational Hand Controller
|-
| '''TVC''' || Thrust Vector Control
|}

== Latest development snapshot ==
The latest development version (possibly unstable) is found in a dedicated [https://sourceforge.net/projects/fgspaceshuttledev/ repository] on SourceForge. You can download the latest snapshot from http://sourceforge.net/p/fgspaceshuttledev/code/ci/development/tarball. Stable updates are pushed to FGAddon periodically.

== Documentation ==

In addition to the original NASA Shuttle Crew Operations Manual and the DPS dictionary which are found in the Documentation/ folder of the spacecraft, a Flight Manual specifically for the operation of the Flightgear simulation is available (standard edition free of charge for Flightgear users):

[[File:Flight manual standard.png|400px|link=http://www.science-and-fiction.org/bookstore.html|alt=Shuttle flight manual|Title Flight Manual]]

(click picture to download)

== Educational Links / Shuttle technical files ==

=== General Space knowledge and tutorials ===

''Basic of Space Flight Book''
https://er.jsc.nasa.gov/seh/spaceflt.pdf

''Thorsten LEO Tools''
https://forum.flightgear.org/viewtopic.php?f=87&t=35213

''Orbiter Space Sim Beginners tutorial''
https://www.youtube.com/watch?v=bOxpvqrqLAo

''FAA Space Basics ( Must read)''
https://web.archive.org/web/20210530202242/https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/cami/library/online_libraries/aerospace_medicine/tutorial/section3/spacecraft_design/

''Rendez Vous Theory''

https://www.baen.com/rendezvous
https://www.baen.com/rendezvous-part2

''Educative links''

Why the wings of the Shuttle Stay on it during Maximal Aerodynamical pressure phase
https://www.aiaa.org/docs/default-source/uploadedfiles/about-aiaa/history-and-heritage/why_the_wings_stay_on-ehrlich.pdf?sfvrsn=801c62b5_0

Space Shuttle Aerodynamics and Flight Dynamics Overview
https://web.archive.org/web/20210127120052/https://www.nasa.gov/centers/johnson/pdf/584730main_Wings-ch4d-pgs226-241.pdf

=== Space Shuttle Systems ===

'''Space Shuttle Systems in depth'''

''Nasa Space Shuttle systems Exhaustive Manual: SCOM''
https://web.archive.org/web/20200602210929/https://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf

''Nasa Data processing system dictionnary, or "What does that page of my shuttle computer"''
https://web.archive.org/web/20210226022241/https://www.nasa.gov/centers/johnson/pdf/359895main_DPS_G_K_7.pdf

''Crew Software Interface ( Nice introduction to Shuttle Computer and handling)''
https://web.archive.org/web/20210226022249/https://www.nasa.gov/centers/johnson/pdf/383444main_crew_software_interface_21002.pdf

'''Workbooks ( Detailled part on some Shuttle systems and procedures, SCOM complement)'''

''APU (How Hydraulic is provided to Shuttle systems''
https://web.archive.org/web/20210226022251/https://www.nasa.gov/centers/johnson/pdf/383439main_apu_hyd_wsb_21002.pdf

''Air Data Systems (What are the equivalent of Pitot Tubes in the Shuttle)''
https://web.archive.org/web/20210226021921/https://www.nasa.gov/centers/johnson/pdf/383438main_air_data_system_workbook_21002.pdf

''Environmental Control and Life Support System ( How is cooled the Shuttle )''
https://web.archive.org/web/20210226004654/https://www.nasa.gov/centers/johnson/pdf/383445main_eclss_21002.pdf

''Navigation Aids ( or how the Shuttle find precisely the runway during entry)''
https://web.archive.org/web/20210226022247/https://www.nasa.gov/centers/johnson/pdf/383450main_navigation_aids_workbook%2021002.pdf

''Intact Ascent Aborts ( Procedures after ONE engine failure)''
https://web.archive.org/web/20210226022307/https://www.nasa.gov/centers/johnson/pdf/383447main_intact_ascent_aborts_workbook_21002.pdf

''Contigency Aborts Procedures after more than ONE engine failure/degradation''
https://web.archive.org/web/20210226011554/https://www.nasa.gov/centers/johnson/pdf/383441main_contingency_aborts_21007_31007.pdf

''And much more that are not publicly available but findable here after a subscription ( A true Space Gold Mine)''
https://www.nasaspaceflight.com/l2/

=== Space Shuttle Checklists ===

''Flight Data Files Bible Site''
https://web.archive.org/web/20211020173004/https://www.nasa.gov/centers/johnson/news/flightdatafiles/index.html

''Annotated and condensed one''
[[Flying the Shuttle - Space Shuttle Checklists]]

A bit more organized:

More informations about Flight Data Files in SCOM part 3

'''Normal situation Checklists'''

''Ascent''
https://web.archive.org/web/20210406234707/https://www.nasa.gov/centers/johnson/pdf/567068main_ASC_135_F_1.pdf

''Post Insertion''
https://web.archive.org/web/20210417211853/https://www.nasa.gov/centers/johnson/pdf/567074main_PI_135_F.pdf

''On Orbit''
https://web.archive.org/web/20210417205430/https://www.nasa.gov/centers/johnson/pdf/567072main_ORB_OPS_135_F_1.pdf

''Rendez Vous''
https://web.archive.org/web/20210417202323/https://www.nasa.gov/centers/johnson/pdf/567076main_RNDZ_135_F.pdf

''Deorbit Preparation''
https://web.archive.org/web/20210424062634/https://www.nasa.gov/centers/johnson/pdf/492871main_D-O_G_Q_5.pdf

''Entry''

https://web.archive.org/web/20210424062633/https://www.nasa.gov/centers/johnson/pdf/381558main_ENT_G_H_8.pdf
https://web.archive.org/web/20210417204127/https://www.nasa.gov/centers/johnson/pdf/567069main_ENT_135_F.pdf

'''Non Normal situation Checklists'''

In the Normal situation Checks above, there are off nominal sections to deal with non critical procedures.

For time critical procedures that must be performed within 5 minutes, there are the so called Pocket checklists ( Ascent, Orbit and Entry).
They are almost the same.

''Ascent''

The Ascent PCL contains procedures that safe systems for continued flight. It also contains orbiter systems powerdown procedures.
https://web.archive.org/web/20210407003811/https://www.nasa.gov/centers/johnson/pdf/366508main_APCL_G_O_1.pdf

''Orbit''

At the initiation of the post insertion phase, the Orbit PCL is utilized. This PCL contains critical orbiter systems malfunction responses and powerdown procedures. The orbit PCL often refers to the orbiter Malfunction Procedures (MAL) Book for detailed troubleshooting.

https://web.archive.org/web/20210907221523/https://www.nasa.gov/centers/johnson/pdf/359853main_OPCL_G_M_10.pdf

Contigency Deorbit in case of Severe malfunctions in Orbit ( Loss of cooling systems, or massive elec failure,..) that would lead to a fast deorbit.

https://web.archive.org/web/20210417212721/https://www.nasa.gov/centers/johnson/pdf/359894main_C-DO_G_L_8_P%26I.pdf

''Entry''

The Entry PCL contains critical contingency systems malfunction responses that allow safe continuation of the pre-deorbit through early entry phases along with orbiter systems powerdown procedures.

https://web.archive.org/web/20210424062636/https://www.nasa.gov/centers/johnson/pdf/366509main_EPCL_G_M_11.pdf

=== Space Shuttle Books ===

''To Orbit and Back Again''

Like a SCOM, less cryptic, full of anecdotes.
https://www.springer.com/gp/book/9781461409823

''Into to the Black''

Book about STS 1, it reads like a Thriller
https://www.thespacereview.com/article/2982/

''Shuttle Down''

Book about an hypothetical scenario. What if the Shuttle was launched from vandenberg and would have diverted to Easter Island :)
[url]https://www.goodreads.com/book/show/549127.Shuttle_Down[/url]

== Videos ==

A compilation of in FG Sim videos about the Space Shuttle

[https://www.youtube.com/watch?v=LOpKt2gXQoE Space Shuttle Launch Flight Gear with STS 133 Real Voices]

[https://www.youtube.com/watch?v=bDGIZj4GGxg Space Shuttle RTLS Abort with OPS 6 real guidance]

[https://www.youtube.com/watch?v=ECJjC-i_3l8 Space Shuttle TAEM KSC Runway 33:HAC and Final Approach]

[https://www.youtube.com/watch?v=fbTFKBWYGbE Space Shuttle TAL]

[https://www.youtube.com/watch?v=62ylBBeO-z4 Space Shuttle Autoland in fog]

On orbit timelapse
[https://forum.flightgear.org/viewtopic.php?f=19&t=35234]

== Mission reports ==

A compilation of Space Shuttle stories / mission reports.

''Shuttle approaches contest''
[https://forum.flightgear.org/viewtopic.php?f=19&t=32790]

''The Van Allen Mission''
[https://forum.flightgear.org/viewtopic.php?f=19&t=35011]

''STS 62 Polar Mission''
[https://forum.flightgear.org/viewtopic.php?f=87&t=38916]

''Meeting ISS''
[https://forum.flightgear.org/viewtopic.php?f=19&t=35276]
[https://forum.flightgear.org/viewtopic.php?f=19&t=35316]
[https://forum.flightgear.org/viewtopic.php?f=19&t=35535]

''Meeting Hubble''
[https://forum.flightgear.org/viewtopic.php?f=87&t=36311]

''From Ground to Orbit''
[https://forum.flightgear.org/viewtopic.php?f=19&t=32851]

''From Orbit to Ground''
[https://forum.flightgear.org/viewtopic.php?f=19&t=33167]

''Return to Launch Site''
[https://forum.flightgear.org/viewtopic.php?f=19&t=33030]

''Transoceanic Abort Landing in Zaragoza''
[https://forum.flightgear.org/viewtopic.php?f=19&t=33368]

''Abort Once Around''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34315]

''Contingency Abort: Landing in Bermuda''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34254]

''Contigency Abort: East Coast Abort Landing''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34969]

''Electrical failure and TAL''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34810]

''Impending Loss of Hydraulics and AOA''
[https://forum.flightgear.org/viewtopic.php?f=19&t=35048]

''Fictionnal Mission into Polar Orbit from Vandenberg''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34700]

''Deorbit and Landing in Easter Island''
[https://forum.flightgear.org/viewtopic.php?f=19&t=34229]

''Triple Engine Failure TAL''
[https://forum.flightgear.org/viewtopic.php?f=19&t=35763]

''Massive electrical failures and Contigency Deorbit // Off Nominal Checklist walkthrough''
[https://forum.flightgear.org/viewtopic.php?f=87&t=36862]

''Single Engine TAL after Droop''
[https://forum.flightgear.org/viewtopic.php?f=87&t=40479]

== Gallery ==
{{screenshot cat
| category = Space Shuttle screenshots
| subject = the Space Shuttle
| image = Shuttle FG03.jpg
}}{{-}}
<gallery mode="packed">
KSC_launch_photorealism.webp|KSC launch photorealism
KSC_launch_2_photorealism.webp|KSC launch photorealism
Vandenberg_photorealism.webp|Vandenberg site photorealism
White_sands_photorealism.webp|White Sands site photorealism
Edwards_photorealism.webp|Edwards site photorealism
Bermuda_photorealism.webp|Bermuda site photorealism
Pad_view_inside.jpg|View on the Pad Pilot Side
Rainy_Pad.jpg|Rainy Pad
On_the_pad.jpg|Shuttle Launch
Shuttle_Launch.jpg|Shuttle Launch
Shuttle FG04.jpg|Shuttle Launch
Farewell.jpg|Launch smoke trail
SRB_sep.jpg|SRB separation
Orbital_Speed.jpg|Accelerating to orbital speed
SSME.jpg|Improved visuals of the exhaust flame
The_desk.jpg|Shuttle 3d cockpit
MECO_sep.jpg|External tank separation
On_orbit_view.jpg|A view of Earth after reaching orbit
ET_sep_2.jpg|The ET seen from the Shuttle
Shuttle OMS full.jpg|Full OMS thrust
Light_effect.jpg|Lightings game in Orbit
Shadow_3.jpg|Shadows and lights on the L2 Commander panel
Over_Africa.jpg|The orbiter high over Africa
Payload ops03.jpg|Handling payload with the RMS arm
Payload_lighting.jpg|Payload Lightings
Space Shuttle sunrise.jpg|Sunrise over Antarctica
Over_Antartica.jpg|Sunrise over Antarctica 2
Sunset.jpg|The OV in orbit at Sunset
Sunset_2.jpg|The OV in orbit at Sunset 2
Sunset_rtls.jpg|RTLS Abort
OMS_burn.jpg|Orbital insertion burn at night
Shuttle-landing04.jpg|Atmospheric entry
Glowing_red_2.jpg|Tiles Glowing Red
Roll_reversal.jpg|High bank angle maneuver to control vertical speed
Mach_down.jpg|During TAEM the Space Shuttle goes subsonic
Eastern_Island_approach.jpg|On final approach into Eastern Island Emergency Landing Site
Final_approach_trondheim.jpg|Final in Trondheim
Pre_flare_KSC.jpg|Pre-flare
Flare_KSC.jpg|Flare
Touch_KSC.jpg|Touchdown in KSC
Fin.jpg|Wheels stop in KSC
</gallery>

[[Category:Space Shuttle documentation]]

Shuttle guidance - TAEM/Approach and Autoland guidance

2024-11-21T18:04:18Z

Gingin: New page for TAEM and Approach Shuttle guidance

This section speaks about TAEM and Autoland guidance.

'''Documentations'''

*Space Shuttle TAEM guidance code sum up: [https://ntrs.nasa.gov/citations/19920010688]
*TAEM/Approach Handbooks there: [https://forum.flightgear.org/viewtopic.php?f=87&t=38777]

'''Overview'''

The last link mentionned above is pretty interesting to see the evolution of TAEM guidance and how it was handled.
The main document I used include the Optional TAEM Targeting (OTT) logic that has been used since STS-5 (before the HAC was a circle with less Energy options for test flights).

After STS-5, HAC could be flown with the different options we are used to see .
Overhead or Straight-In HAC; and Nominal Entry Point (7Nm in final) or Minimal Entry Point (4Nm in final)
[[File:OTT option.webp|600px|thumbnail|none]]

Another option called - final radius shrinking - is included in that TAEM guidance version.
It allows the final HAC radius (2.3 Nm) to decrease up to 0.8 Nm if we are low during the HAC.
[[File:Spiral hac.webp|600px|thumbnail|none]]

The whole logic is organized through several functions that are called during all the TAEM phase at a rate between 160 and 980ms.
It ends at 10000 feet (Approach and Landing interface) where the Auto Land logic kicks in (quite the same logic with tighter gains).
[[File:TAEM flow logic.webp|600px|thumbnail|none]]

Let's go briefly through each functions.
The first function that is not mentionned is a frame coordinate converter from a Greenwhich frame into a runway centered frame.
[[File:TAEM runway coordinate system.webp|600px|thumbnail|none]]

=== TAEM ===

'''1) TGXHAC'''

It is the initial TAEM computation where the HAC is defined following what we choose in the Spec 50 display (Runway / Overhead or Straight-In / NEP or MEP / etc)
Aim point is also taken into account (7500 feet or 6500 feet)
[[File:TGXHAC.webp|400px|thumbnail|none]]

Another important factor that is calculated there is the final glideslope value for the A/L final path (starting at 10000 feet / 6Nm).
It can be either 18° for a heavy weight (more than 220000 lbs) or 20° for a lighter Shuttle.
That was changed later in the STS program to take into account the nominal mid-value for Speedbrake effectiveness (65°).
That slope combination was then choosen.
[[File:OGS geometry.webp|600px|thumbnail|none]]

In the november 2024 dev branch, we can clearly see it now at Approach/Landing Interface in the HUD and PFD glideslope deviation.
Left HUD for Heavy / Right for Light
[[File:HUD OGS.webp|600px|thumbnail|none]]

'''2) GTP (Ground Track Computations)'''

The distance to the runway is computed in that function.

*Left and Center Picture (Before and into the HAC): The range to go is the sum of the distance to be flown while aligning with the HAC entry point(ARCAC), the distance to be flown to that tangent WP1 (RTAN), the distance to be flown into the HAC up to the threshold (RPRED2)
*Right picture: Once close enough to the final runway course, distance forecasted becomes a direct distance to the runway threshold.
[[File:GTP overview.webp|600px|thumbnail|none]]

'''3) TGCOMP (General Computations)'''

All the computations for reference parameters are done there.

*The Altitude reference
A mix between linear and cubic segments.
Up to 40 Nmish in blue, a low slope linear profile (6° ish of slope)
Between A/L interface ( 6Nm) and 40 Nm, the green cubic segment where the slope increases up to the final Gamma targeted (18/20°)
At A/L interface, the red linear segment for final slope.
[[File:TAEM altitude profile.webp|600px|thumbnail|none]]

*The Specific Energy reference
That allows to shape the Nominal Energy path based on the True Airspeed and Altitude.
S-turn / Nominal / Low Energy boundaries.

Left picture is the Energy lines I took as a reference (closer to the latest Energy profiles flown in the later part of STS program )
Right picture shows that those lines are "just" some linear functions with some breakpoints here and there.
[[File:TAEM EW.webp|600px|thumbnail|none]]

*Dynamic Pressure Reference Profile
It is basically the EAS targeted.
[[File:TAEM QBAR.webp|600px|thumbnail|none]]

I adjusted it also to be closer to the latest QBAR profile flown (a tad higher, 305 psf targeted at A/L ie. 300 kts instead of 275 kts)
It will be coherent with the EAS visible in the Vert Traj display.
[[File:TAEM mm305.webp|600px|thumbnail|none]]

Another small logic for Low Energy handling: ''HAC radius shrinking''.

The final HAC radius (past 90° into the HAC) is 14000 feet (2.3 Nm).
In case of Low Energy once into the HAC and before the 90° HAC angle to go, the final radius will shrink depending on how Low we are in Potential Energy (up to a final radius of 5000 feet).
Basically, it means to be 4000 feet ish low on the glidepath once into the HAC.
[[File:HAC shrink theory.webp|600px|thumbnail|none]]

An example below.
Right picture: Nominal energy situation (final radius of 2.2Nm).
Left picture: Slightly off nominal energy situation, HAC final radius shrinked to 1.8 Nm and Shuttle was smoothly brought back on the glide.
[[File:HAC shrink example.webp|600px|thumbnail|none]]

'''4) TGTRAN (Transition between TAEM phases)'''

Here is handled the boundaries between the different part of the TAEM and Autoland (Acquisition / HAC / Pre final / Outer Glide Slope / etc)
It works like a big Lego, and it will be easy for example to link it later to the RTLS logic with the phases 4 to 6.
[[File:TAEM iphase.webp|600px|thumbnail|none]]

The S-Turns are also commanded in that function for example.
A sanity check is done to turn away from the HAC. Once the Total Energy is closed to the Nominal one, IPHASE 0 is exited and we go back to the Acquisition logic (IPHASE 1).
[[File:TAEM sturn.webp|600px|thumbnail|none]]

'''5) TGNZC (Nz Commanded)'''

The output for the Pitch AP is done there, under the form of a radial acceleration that will be converted later in to a pitch rate and sent into the AP loop.
All the functions calculated in the TGCOMP will be used there to limit that commanded Nz (NZC).
MIDVALUE function is like a Nasal clamp function.

The first NZC computed is for the altitude error, then it goes through an energy error check, then QBAR, and finally a Max Nz filter to clamp the NZC between -0.5 g and +0.5g.

An example.
If we are low: positive NZC computed to Pitch Up and come back to the reference altitude.
If we are high on energy, a less positive NZC is then outputted to not go too high on energy.
If we are too close to QBAR boundaries, NZC is adjusted to stay away from a hazardous aerodynamical pressure condition.
Finaly, if we are approaching the max radial G's tolerated, the NZC is limited again to avoid breaking the wings.
A quite strong and intricated pitch command loop.
[[File:TGNZC.webp|600px|thumbnail|none]]

''Pitch channel''

The TAEM pitch command loop is based on a commanded radial acceleration (NZC) converted into a pitch rate which is sent to the AP loop for the correct elevon deflection.
Gains and refresh rate depends on TAEM and Autoland phases.
Everything is filtered several times to have some stable outputs.

*Delta Nz commanded is based on the altitude and altitude rate error ( glidepath deviation).
*It goes then through an Energy filter to avoid to be too high or low on energy ( right ladder on MM 305)
*Next filter is a dynamic pressure one to avoid over/underspeed situations.
*Last filter is a Pitch Nz limit (0.5 g) to avoid to break the wings (2g for a 60° of bank turn plus 0.5g for the max pitch commanded ----> 2.5g max for structural considerations)
[[File:TAEM pitchchanne.webp|600px|thumbnail|none]]

'''6) TGSBC (Speedbraked Commanded)'''

It handles the SB logic.
SB setting is fixed to 65° until Subsonic.
In subsonic, position commanded is a function of reference Energy and Qbar errors until final where the logic is blended into a QBAR error only up to 3000 feet.
From there, a fix setting is commanded for Pre-Flare (Highlighted in the second page there: [https://forum.flightgear.org/viewtopic.php?f=87&t=38777&start=15]).
That replicates with a great accuracy the original speedbrake logic; fixed setting above Mach 1 (65°) and Energy/Qbar modulation in Subsonic.
Once in final, speedbrakes will control the EAS error (300 kt targeted on Outer Glide Slope).

''Small interesting points''

*Function takes into account the rate limitation depending on the number of hydraulic systems operational.
If more than one system is op, SB opening rate is 5°/s and closing rate is 10°/s
If just one system is op, SB opening and closing rate is 5°/S

*At 3000 feet, there is a first SB retract that takes into account many parameters explained page 2 of that topic: [url]https://forum.flightgear.org/viewtopic.php?f=87&t=38777&start=15[/url]
The complete logic page 73 (4-4) of that Handbook: [https://gandalfddi.z19.web.core.windows.net/Shuttle/JSC-23266%20-%20Approach,%20Landing%20and%20Rollout%20Flight%20Procedures%20Handbook%20-%20Rev%20B%20200505.pdf].
Another parameterwas added, the Altitude Density variation which is a function of the ISA deviation.
High ISA deviation leads to a thiner atmoshpere and a longer flare forecasted, hence a higher SB setting to avoid that over energy situation (and Vice-Versa).

An example there with an ISA deviation of 30 °.
Density altitude is 6129 feet and pressure one is 2264 feet (120ft in addition for every degrees above ISA)
That gives a SB retract of 28° instead of 15° with ISA 0
[[File:SB retract.webp|600px|thumbnail|none]]

*At 500 feet, the windshift between 3000 and 500 feet is taken into account to adjust one last time the SB position.
That is useful in case of gusty conditions with some late wind changes close to the ground.

An example with a stormy and gusty day (up to 30kt).
We lost 15 kt of effective wind since we have past 3000 feet AGL. That is some additional tailwind then and the SB will retract from 23 to 15° to take into account that sudden loss of lift caused by the windshear in order to avoid a hazardous sink rate.
[[File:SB retract 2.webp|600px|thumbnail|none]]

'''7)TGPHIC (Bank commanded)'''

Here is done the bank commanded sent to the AP.
It depends on the Phase we are in.

From Left to Right.
*IPHASE 0 (S-turn): A constant bank is commanded away from the HAC
*IPHASE 1 (HAC acquisition): A bank proportionnal to the delta azimuth (DPSAC) with the WP1 is commanded (2.5 * delta azimuth)
*IPHASE 2 (In HAC): A bank proportionnal to the the HAC cross range and radial velocity is commanded.
*IPHASE 3 (Pre Final): A bank proportionnal to the final axis cross range / cross range variation /cross range integral is commanded.
[[File:TGPHIC.webp|600px|thumbnail|none]]

For the Autoland phases , it is similar to the Pre Final with different Gains.
[[File:TAEM autoland phase.webp|600px|thumbnail|none]]

=== From TAEM to Approach/Autoland handover ===

Landing site threshold coordinates need to be very precise for an autoland.
''They have been adjusted for KSC/VBG/EDW/ZZA/FMI/IPC/HAO/JDG/KEF/YQX/PAR/INN so far''.

At 10000 feet, the TAEM logic is ended and Autoland logic kicks in.
It is fairly similar to the TAEM one, with tighter deadbands and additionnal closed loop guidances for the last part (flare,...)

Three parts: Outer Glideslope tracking up to 2000 feet (blue) / Circular pull up flare to decrease the glideslope from 19°ish up to 1.5° (red) / 1.5° Inner Glide Slope and final flare (green)
[[File:Autoland altitude tracking.webp|600px|thumbnail|none]]

*Outer Glide Slope tracking.
Either 18° or 20° depending of the weight.
Aim point will also slightly modified the downrange and final flare
[[File:Autoland OGS.webp|600px|thumbnail|none]]

*Flare and Inner Glide Slope intercept
At 2000 feet, a 1.3gish pull up is commanded to transition from the steep glideslope to a shallower one (combination of open and closed loops).
An exponential decay to the inner glide slope allows a smooth transition during that pull up maneuver.
Aim is to have at least 5 seconds on the 1.5° slope before the final flare.
[[File:AUtoland flare IGS.webp|600px|thumbnail|none]]

*Final Flare
At 80 feet QFE, another pull up is commanded to decrease the rate of descent.
Aim is to land 2500 feet past the runway threshold.
There are however some dispersions due to winds, ground effect, and some unforseen parameters.
The guidance is quite resilient for a wide range of situations and should be able to bring down safely the Orbiter not far from the targeted touchdown zone.
[[File:Autoland final flare.webp|600px|thumbnail|none]]

More time to watch the sunset while autopilot is on.
[[File:Sunset landing.webp|600px|thumbnail|none]]

File:Sunset landing.webp

2024-11-21T18:00:04Z

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File:HAC shrink example.webp

File:Spiral hac.webp

2024-11-16T09:44:18Z

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2024-11-06T22:14:02Z

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2024-11-06T22:14:02Z

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