1,360
edits
Flying the Shuttle - Abort Procedures Overview: Difference between revisions
Jump to navigation
Jump to search
Flying the Shuttle - Abort Procedures Overview (view source)
Revision as of 12:12, 8 September 2015
, 8 September 2015→Return to Launch Site
| Line 35: | Line 35: | ||
The abort is declared after SRB separation outside the atmosphere. From there, there are three distinct phases - powered flight, coast and ET separation and final glide. | The abort is declared after SRB separation outside the atmosphere. From there, there are three distinct phases - powered flight, coast and ET separation and final glide. | ||
The powered flight phase starts extremely low on thrust. At that stage, the main aim is to deplete propellant. Pitched highly upwards (up to 60 deg) to vector thrust downward and minimize loss of altitude, the Shuttle continues to accelerate downrange. At a turning point, the Shuttle then pitches around rapidly (about 10 deg/s) and starts to decelerate, still vectoring thrust downward. All the time the trajectory drops, and pitch should be adjusted such that by the time of MECO, it has come down to about 220.000 ft but not significantly lower | The powered flight phase starts extremely low on thrust. At that stage, the main aim is to deplete propellant. Pitched highly upwards (up to 60 deg) to vector thrust downward and minimize loss of altitude, the Shuttle continues to accelerate downrange. During this time, the OMS propellant already has to be dumped (by burning it) - {{Key press|Control|o}} activates the OMS fuel dump. If this is not done, the Shuttle's CoG will be off by the time it needs to glide, with usually catastrophic consequences. | ||
At a turning point, the Shuttle then pitches around rapidly (about 10 deg/s) and starts to decelerate, still vectoring thrust downward. All the time the trajectory drops, and pitch should be adjusted such that by the time of MECO, it has come down to about 220.000 ft but not significantly lower | |||
[[File:Shuttle RTLS abort01.jpg|600px|The Space Shuttle during an RTLS abort - after pitch around]] | [[File:Shuttle RTLS abort01.jpg|600px|The Space Shuttle during an RTLS abort - after pitch around]] | ||
| Line 70: | Line 72: | ||
[[File:Shuttle RTLS abort03.jpg|600px|The Space Shuttle during an RTLS abort - after ET separation]] | [[File:Shuttle RTLS abort03.jpg|600px|The Space Shuttle during an RTLS abort - after ET separation]] | ||
Since the Shuttle is just feeling the fringes of the atmosphere, it will start to drop rapidly (i.e. almost accelerating 9.8 m/s downward every second) and plunge into the dense atmosphere. As soon as the atmosphere catches, forces will ramp up quickly. The aim of the next few seconds is to survive this. | Since the Shuttle is just feeling the fringes of the atmosphere, it will start to drop rapidly (i.e. almost accelerating 9.8 m/s downward every second) and plunge into the dense atmosphere. As soon as the atmosphere catches, forces will ramp up quickly. The aim of the next few seconds is to survive this. Short of a contingency abort, the plunge into the atmosphere from RTLS MECO is probably the most dramatic maneuver you will ever experience in the Shuttle. | ||
Pitch needs to be brought up rapidly to 50 deg and the Aerojet DAP needs to be on. The Shuttle may reach vertical speeds in excess of 500 m/s before the atmosphere shows significant effect. Then watch acceleration ramp up - as soon as the acceleration reaches 2.2 g, pitch has to be reduced to lessen the forces. Pitch needs to be managed such as to keep the acceleration on the vehicle close to that number till the acceleration lessens and the vertical speed reduces to less than 100 m/s. | Pitch needs to be brought up rapidly to 50 deg and the Aerojet DAP needs to be on. The Shuttle may reach vertical speeds in excess of 500 m/s before the atmosphere shows significant effect. Then watch acceleration ramp up - as soon as the acceleration reaches 2.2 g, pitch has to be reduced to lessen the forces. Pitch needs to be managed such as to keep the acceleration on the vehicle close to that number till the acceleration lessens and the vertical speed reduces to less than 100 m/s. | ||
If the Shuttle survived the contact with the atmosphere, the remaining task is to manage azimuth and range to the site. For this, one returns to the normal techniques of flying Mach-dependent AoA and using bank angle to manage sink and drag or S-turns for ranging, all intended to bring the Shuttle to a regular TAEM interface. | If the Shuttle survived the contact with the atmosphere, the remaining task is to manage azimuth and range to the site. For this, one returns to the normal techniques of flying Mach-dependent AoA and using bank angle to manage sink and drag or S-turns for ranging, all intended to bring the Shuttle to a regular TAEM interface. | ||
To initiate an RTLS abort in FG, the entry guidance computer needs to be set to the launch site and as abort mode 'RTLS abort' needs to be selected. In response to this, the HUD symbology changes to show key information needed to pilot the abort, such as the distance and relative velocity to site and the percentage of propellant remaining. | |||
[[File:Shuttle RTLS abort02.jpg|600px|HUD symbology of the Space Shuttle during RTLS abort]] | |||
The groundtrack of an RTLS abort is an elongated loop, heading out into the launch direction before returning almost the same path: | |||
[[File:Shuttle RTLS abort05.jpg|600px|Groundtrack of a Space Shuttle RTLS abort]] | |||
== Further reading == | == Further reading == | ||
[http://spaceflight.nasa.gov/shuttle/reference/shutref/events/aborts/ NASA human spaceflight page on abort modes] | [http://spaceflight.nasa.gov/shuttle/reference/shutref/events/aborts/ NASA human spaceflight page on abort modes] | ||