Orion abort modes

The Orion Multi-Purpose Crew Vehicle (Orion MPCV) is a class of partially reusable spacecraft used in NASA's human spaceflight programs. Consisting two components – a Crew Module (CM) manufactured by Lockheed Martin, and a European Service Module (ESM) manufactured by Airbus Defence and Space – the spacecraft are designed to support crewed exploration beyond low Earth orbit. Orion is equipped with solar power, an automated docking system, and glass cockpit interfaces modeled after those used in the Boeing 787 Dreamliner, and can support a crew of six up to 21 days undocked and up to six months docked. A single AJ10 engine provides the spacecraft's primary propulsion, while eight R-4D-11 engines and six pods of custom reaction control system engines developed by Airbus provide the spacecraft's secondary propulsion. Although compatible with other launch vehicles, Orion is primarily designed to launch atop a Space Launch System (SLS) rocket, with a tower launch escape system.

Technicians carefully position an Orion flight test crew module to be airlifted. This module was planned to be used for a launch abort system pad-abort flight test.

The earlier Apollo system had various abort modes depending on altitude, velocity, and other circumstances. Likewise the Orion will have similar modes of operation for its launch performance aborts. Some of these may not use the LAS itself, but would use the second stage of the SLS, or even the Orion vehicle's own propulsion system (the Aerojet AJ10 engine) instead.

Initially designed to land on solid ground, like that of the early and current Soviet and Russian crewed spacecraft (Vostok, Voskhod, and Soyuz), with a water landing as a backup, in August 2007, NASA tentatively redesigned the Orion for water landings (splashdowns) as the primary mode of landing, with ground landings as the emergency backup.[1] Under the advice of the Exploration Systems Architecture Study (ESAS) report, NASA will most likely develop abort procedures that resemble the abort procedures used on Apollo, but with some procedures carried over from the Shuttle.

Modes

The method of abort, either using the LAS or the second stage of the Space Launch System booster, depends on how far into the flight the spacecraft and crew are traveling.

Prelaunch

NASA has acquired several MRAPs to station near the launch pad, should there be time for the crew to evacuate the vehicle. One will be occupied by emergency rescue personnel, while the other will stand empty behind a blast shelter.[2] Pad emergency egress enables astronauts and engineers to quickly escape the perimeter of the rocket. Both zip-lines and roller coasters were at one time studied for this purpose.[3]

Mode one
See also: Pad Abort 1 and Ascent Abort-2

During the first 120 seconds of flight, up to the jettisoning of the solid-fueled boosters at 300,000 feet (91 km), the Orion crew module (CM) will separate from the rest of the rocket propelled by the LAS. Unlike the Apollo Launch Escape System, which used a pair of canards and the weight of the spacecraft to flip the vehicle over for landing, the Orion LAS has a set of steering rockets that will steer the spacecraft away from the malfunctioning SLS, as well as prepare the spacecraft for both separation and splashdown. The tower will then be jettisoned 14 seconds later and the hypergolic fuel on the Orion CM would be automatically released at a pre-determined altitude.

Mode two

After the LAS is jettisoned, the Orion will separate as a whole from the SLS and either use its large AJ-10 engine or smaller control engines to maneuver from the rocket. Similar to a Space Shuttle trans-Atlantic (TAL) abort profile, the Orion will use the AJ-10 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.

Mode three

The SLS would propel the Orion into an initial orbit, upon which the spacecraft will immediately separate, and then perform a retrofire that will allow the Orion CM to splashdown in the Pacific Ocean off the U.S. West Coast, or make a ground landing 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.

Mode four

If the SLS suffers less-than-ideal performance during the initial orbit insertion, it can be restarted 45 minutes later to place the Orion 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.

See also

References
  2. MRAP Rolls Through Pad Evacuation Runs
  3. nasaspaceflight.com, September 2012
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