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Flying the Shuttle - Abort Procedures Overview: Difference between revisions
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Flying the Shuttle - Abort Procedures Overview (view source)
Revision as of 15:19, 15 October 2015
, 15 October 2015→Transatlantic Abort Landing
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The Transatlantic Abort Landing (TAL) is the next option in terms of energy required after the RTLS abort. It is based on bringing the Shuttle onto a ballistic trajectory that doesn't quite reach orbital speed and aim the trajectory at a landing site on the other side of the Atlantic ocean - dependent on launch course, there are several sites available. | The Transatlantic Abort Landing (TAL) is the next option in terms of energy required after the RTLS abort. It is based on bringing the Shuttle onto a ballistic trajectory that doesn't quite reach orbital speed and aim the trajectory at a landing site on the other side of the Atlantic ocean - dependent on launch course, there are several sites available. | ||
TAL capability somewhat overlaps with RTLS capability - if both are possible, TAL is usually the preferred pattern because the way the Shuttle is operated during a TAL is much closer to nominal operations. | |||
The decision to fly a TAL needs to be made early on. From this point on, the landing site needs to be selected, and the trajectory needs to be aimed at the landing site, for which guidance will compute an azimuthal deviation. This might require a change in launch course. | |||
[[File:Shuttle_TAL01.jpg|600px|TAL abort decision after engine flameout]] | [[File:Shuttle_TAL01.jpg|600px|TAL abort decision after engine flameout]] | ||
OMS fuel dump needs to start immediately. Dependent on when the abort is declared, there may not be enough time for a complete dump of OMS fuel, in which case the engines may be throttled down in the last stage of the flight to get extra time prior to MECO. At MECO, the OMS fuel dump needs to be completed and the ballistic trajectory endpoint needs to be within cross-range capability (ideally some 500 miles) of the landing site. | |||
After MECO, things get hectic quickly as the Shuttle will get back into the atmosphere fast. Tasks that normally are done within 30 minutes need to be executed in about three minutes. First, the ET needs to be separated and the umbilical door closed to get full protection from the heat shield. Then the main engine fuel dump needs to be initiated, and finally the transition to MM 301 and the entry DAP needs to be made. At the same time, dumping the forward RCS fuel is a good idea. | |||
[[File:Shuttle_TAL02.jpg|600px|Fuel dump during TAL entry planning]] | |||
Once the Shuttle is prepared for entry (i.e. ET separated, thermal protection operational, entry DAP selected, attitude controlled), the rest of the TAL resembles a nominal entry, except the needed deceleration may be a bit higher than usual. Ranging is done by drag control during entry, aiming for a nominal TAEM interface sixty miles from landing site, from which point a nominal TAEM is flown. | |||
A TAL abort takes about 45 minutes from launch to touchdown, which is short enough that the APUs can be left running for the whole duration of the flight. | |||
== 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] | ||