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One of Columbia's 3 auxilary power units fails pre-landing test
Columbia Shuttle still can come down Sunday
May 2, 1998
Web posted at: 12:38 p.m. EDT (1638 GMT)JOHNSON SPACE CENTER, Texas (CNN) -- A power unit used by space shuttle Columbia for steering during the critical landing phase has failed a pre-landing test, but NASA says the shuttle should be able to land safely.
The system, called an auxiliary power unit, is used to power the rudder and steering surfaces on the shuttle's wings and the landing gear brakes.
Columbia has three APUs, and the crew tested only one in Saturday morning's pre-landing check. The shuttle can land safely with the remaining two, but landing procedures may be changed, officials said. If a second APU fails, the shuttle could still land, but the controls in the cockpit would be sluggish and steering would be possible, but difficult.
Columbia and its seven-person crew are scheduled to land just after noon EDT Sunday.
NASA spokesman Steve Nesbitt told CNN the problem will have "no serious effect to the mission." The problem has occurred on one other flight.
The power unit generates lots of heat as it spins up to the proper speed and needs to be cooled by an onboard system as it operates. The cooling unit, called a flash evaporator, is what failed in the pre-landing test.
The power units are used only on takeoff and landing. The one which failed Saturday also experienced difficulty during Columbia's April 17 launch. Flight controllers suspected then the system might be frozen and that it would thaw during the 16-day flight. That's why they had the crew test it Saturday.
The remaining two power units will be turned on an hour before landing on Sunday, officials said. The third, faulty one will be activated just before landing so it will only have to run for a short time, easing its cooling system problem.
Correspondent John Holliman contributed to this report.
Related stories:
- TheView from Space: Of rats and men
- Astronauts repair Columbia's carbon dioxide system - April 25, 1998
- Trouble aboard Columbia may force early landing - April 25, 1998
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