Space Shuttle: Difference between revisions

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.

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.

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.

=== OMS DAP schemes  ===

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.

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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.

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

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.

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.

== Glossary of acronyms ==