Engine replacement on tap

NASA will replace one of shuttle Discovery's three liquid-fueled main engines, but the work is not expected to delay its targeted July 1 launch on the agency's second post-Columbia test flight.

Engineers examining an engine at Stennis Space Center in Mississippi recently discovered a cracked solder joint on one of two power supplies associated with its computer controller.

The failure of both in flight would cut power to the controller. The controller operates in conjunction with engine sensors, valves, actuators and spark igniters to provide for engine control, checkout and monitoring.

Engineers think the crack might have been caused by the high number of thermal cycles the engine had been put through over the course of time.

In a meeting this afternoon, managers decided to change out the No. 2 engine on Discovery as a precaution because it has a similar thermal cycle history.

Preps for the engine removal will begin tonight. The actual removal is scheduled for April 18 and a replacement will be installed April 20.

Discovery remains scheduled to move from its processing hangar to the Kennedy Space Center Vehicle Assembly Building on May 12. Launch remains scheduled for July 1.