Countdown! - Pad Abort 1 Nearly Ready
NASA's latest flight test for future human space exploration, the Launch Abort System Pad Abort 1, or PA-1, test is set for May 6 at the U.S. Army White Sands Missile Range near Las Cruces, N.M.
Although the Orion is a component of the agency's Constellation program, the future of which is currently under Congressional review, the test is part of NASA's ongoing mission to develop safer space vehicles for all human spaceflight applications. Information gathered through PA-1 testing will be valuable in design and development of future systems built for use in providing safe crew escape in the event of emergency. The launch abort system, or LAS, could be used on the launch pad or during the first stage of ascent to orbit.
The LAS comprises three solid propellant rocket motors: an abort motor, an attitude control motor and a jettison motor. The primary motor is the abort motor, which is used to propel the crew module away from the pad. The attitude control motor steers the vehicle so as to maintain its stability and reorient it as needed. The jettison motor will pull the whole launch abort system away from the crew module and make way for parachute deployment and landing. In addition to the motor stack, the LAS contains a fairing assembly that covers the crew vehicle and a nose cone.
During the test, an abort command will be sent from the mobile operations facility that will ignite both the LAS abort and attitude control motors. The abort motor will burn for approximately six seconds, with the highest impulse in the first 2.5 seconds. The crew module will reach approximately 445 miles per hour in the first three seconds in its upward trajectory away from the pad, reaching an altitude of about one mile.
The attitude control motor will fire simultaneously with the abort motor and provide adjustable thrust vectoring to keep the crew module on a controlled flight path. As burnout of the abort motor concludes, the launch abort vehicle will be reoriented in preparation for a programmed sequence of events. Explosive bolts will fire and the jettison motor will discard the spent abort system from the boilerplate crew module to allow deployment of the recovery parachute system.
The attitude control motor, which encompasses eight thrusters producing up to 7,000 pounds of thrust, was developed at Minneapolis-based Alliant Techsystems, or ATK. The firm also developed the abort motor, which can produce a momentary half-million-pound thrust as it pulls the capsule away from the launch pad. Aerojet, headquartered in Sacramento, developed the jettison motor, which is the only motor of the three that would be used in all flight cases to pull the escape tower from the crew module.
The crew module for the PA-1 test was moved to the launch pad March 23. Technicians next will stack the launch abort system motors atop the module and, during the next five weeks, conduct combined systems tests leading to the actual flight test.
Brent Cobleigh, Dryden director of Exploration Systems said that the NASA team at White Sands has completed integration of all systems, pyrotechnic devices and parachutes into the crew test module.
Jay N. Estes, deputy manager in the Orion Flight Test Office at Johnson Space Center, Houston, congratulated the NASA and contractor team that has been laboring for more than two years to bring the launch abort system to actual flight test.
"It is a huge accomplishment for the Pad Abort 1 team that we have achieved this milestone," he said. "It's been a long tough effort, but we're almost done!"
After integrating the final rocket motor - the attitude control motor - with the rest of the launch abort system, a joint NASA/Lockheed Martin team connected the system electronics to the crew module for a series of integrated tests in a hangar. During these tests, special equipment simulated abort of a launch with the vehicle still on the launch pad - essentially "fooling" the vehicle systems into believing that the vehicle was flying an abort sequence. The abort simulation allowed the team to verify that all systems are ready.
The test module and launch abort system stack were built at Langley Research Center in Virginia. Systems installation and integration took place at Dryden. The module was airlifted to White Sands last August.
By Jay Levine