Leaky shuttle power unit replaced

NASA contractor technicians are hooking up a spare hydraulic power device aboard shuttle Discovery today after replacing a leaky unit.

The so-called Auxiliary Power Unit is one of three devices that play critical roles during shuttle launches and landings.

The units provide the hydraulic power needed to steer the shuttle's three liquid-fueled main engines during an 8 1/2-minute climb into orbit. They also are key to operating the orbiter's wing flaps, rudder speedbrake and landing gear during a gliding freefall back to Earth.

The removal and replacement work will not have an impact on NASA plans to move the orbiter from its hangar to the Kennedy Space Center Vehicle Assembly Building in mid-April. NASA hopes to launch Discovery on the agency's second post-Columbia test flight around May 10.