Orion abort modes
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The upcoming NASA Orion spacecraft, which will replace the Space Shuttle after 2010, will have a launch escape system (LES) similar to that employed for the Apollo Command Module. The LES is a powerful solid rocket mounted in a tower above the Orion spacecraft which in an emergency would pull the spacecraft away from the booster vehicle.
The earlier Apollo system had various abort modes depending on altitude, velocity, and other circumstances. Likewise the Orion LES will have similar modes of operation. Some of these may not use the LES itself, but the Orion vehicle's own propulsion system.
The Orion spacecraft was originally designed to land on both solid ground and in the water, but as of August 2007 was redesigned for water landings only. NASA, under the advice of the Exploration Systems Architecture Study (ESAS) report, will most likely develop abort procedures that resemble the abort procedures used on both Apollo and Space Shuttle.
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[edit] Modes
The method of abort, either using the LES or the second stage of the Ares I booster, will depend on how far into the flight the spacecraft and crew are traveling.
[edit] Mode One
- Alpha
- During the first 42 seconds of flight up to 3 km, the Orion Crew Module (CM) will separate from the rest of the rocket propelled by the Launch Escape System (LES), with small solid-fuelled engines at the top steering the capsule towards the east over the sea and away from the rocket. The tower will then be jettisoned 14 seconds later and the hypergolic fuel on the Orion CM would be automatically released.
- Bravo
- From 3 to 30.5 km, after the capsule had moved away from the rocket, canards will be deployed by the tower to force the CM/LES combination into a CM-forward (blunt) position.
- Charlie
- From 30.5 km until the LES is jettisoned just after second stage ignition, the CM reaction control system would be used to force the CM/LES combination into the CM-forward position as the canards would have little effect in the now thin air.
[edit] Mode two
After the LES is jettisoned, the Orion Crew and Service Modules (CSM) will separate as a whole from the Ares I rocket and either use its large engine or smaller control engines to manoeuvre from the rocket. Similar to a Space Shuttle Trans-Atlantic (TAL) abort profile, the CM will use the SM engine to propel the spacecraft to a desired separation point, in which then the Orion CM would land in either western Spain or Morocco on "due east" (i.e. lunar) flights, or in Ireland or the United Kingdom on ISS-bound flights. A splashdown in the eastern Atlantic Ocean would only be a contingency.
[edit] Mode three
The Ares I would propel the Orion CSM into an initial orbit, upon which the spacecraft will immediately separate, and then perform a retrofire that will allow the Orion CM to land at either Edwards Air Force Base in California or White Sands Space Harbor in New Mexico. This is similar in profile to the Shuttle's "Abort Once Around" (AOA) profile.
[edit] Mode four
If the Ares I suffers a less-than-ideal performance during the initial orbit insertion, it can be restarted 45 minutes later to place the Orion CSM into a less than ideal orbit that can be corrected with the on-board propellant reserves later in the flight. This is similar to the Shuttle's "Abort To Orbit" (ATO) profile, but depending upon the stable orbit reached, it may require NASA to end the mission with a landing at either Edwards or White Sands within a 24 hour period.
[edit] See also
[edit] References
- Full ESAS report
- august 2007 official NASA document -- NASA has not completely abandoned the "land landing" option
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