Space shuttle Endeavour to launch no earlier than May 16
Technicians are continuing work to resolve an issue in a heater circuit associated with Endeavour's hydraulic system.
May 9, 2011
NASA managers have retargeted space shuttle Endeavour's launch to no earlier than Monday, May 16. After a meeting May 6, they also extended the length of Endeavour's STS-134 mission to the International Space Station from 14 to 16 days. If Endeavour launches May 16, liftoff would be at 8:56 a.m. EDT.
At Launch Pad 39A, the access door is open on space shuttle Endeavour for technicians to enter the aft area where the Load Control Assembly-2 (LCA-2) is located. NASA/Troy Cryder
At 3 p.m. Monday, May 9, Mike Moses and Mike Leinbach from NASA’s Space Shuttle Program will hold a news conference at Kennedy Space Center in Florida to discuss the progress of repairs since Endeavour's launch postponement April 29.
Kennedy technicians are continuing work to resolve an issue in a heater circuit associated with Endeavour's hydraulic system that resulted in the launch postponement. Technicians 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 May 4, and a test of nine shuttle systems powered by the new box is underway.
This past weekend, technicians installed and checked out new wiring that bypasses the suspect electrical wiring connecting the switchbox to the heaters. They also ran the heaters for up to 30 minutes to verify they are working properly and completed retesting of the other systems powered by the switchbox.
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.
Launch attempts are available through May 26. May 21 is the only day a launch is not an option because it would lead to a May 23 docking with the space station. May 23 is when three of the space station's Expedition 27 crew members undock and return home in their Soyuz spacecraft. 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.