Space Shuttle Endeavour to launch no earlier than 16 May
NASA managers have retargeted Endeavour's launch to no earlier than Monday, 16 May. After a meeting on Friday, they also extended the length of STS-134 mission to the International Space Station from 14 to 16 days. If Endeavour launches on 16 May, liftoff would be at 14:56 CEST.Engineers at NASA’s Kennedy Space Center are continuing work to resolve an issue in a heater circuit associated with Endeavour's hydraulic system that resulted in the launch postponement.
They determined the failure was inside an aft load control assembly, which is a switchbox in the shuttle's aft compartment, and possibly its associated electrical wiring.
Although the root cause of the failure in the switchbox has not been found, technicians are replacing hardware that could have caused the problem. The faulty box was changed last Wednesday, and a test of nine shuttle systems powered by the new box is under way.
The shuttle has three Auxiliary Power Units (APUs) that provide hydraulic power to steer the vehicle during ascent and entry. The hydrazine fuel lines on each APU have two heater circuits that prevent the fuel from freezing while the shuttle is in space.
NASA launch commit criteria and flight rules require all APUs and heater circuits to be operational for launch. On Endeavour's first launch attempt, one of two heaters for APU-1's fuel line did not work. Engineers confirmed the circuit in the original switchbox that directed power to the heaters was shorted out.
Managers reviewed the STS-134 mission timeline and determined the Endeavour crew can accomplish all objectives even with the departure of the three station crew members.