Technical issues that caused the delay of Endeavour's last launch have pushed liftoff to no earlier than May 8.
Technicians and engineers at NASA's Kennedy Space Center in Florida have identified the likely source of what caused heaters on a fuel line for space shuttle Endeavour's auxiliary power unit-1 (APU-1) to fail April 29, scrubbing the first launch attempt for the STS-134 mission. The failure appears to be a power problem within the aft load control assembly-2 (ALCA-2), a box of switches controlling power feeds, the space agency reported.
"That basically means the power is not getting out to the heaters that weren't working on launch day," said Mike Moses, space shuttle program launch integration manager. "We can tell you, pretty much, that [Endeavour's launch is] not going to be any earlier than May 8," Moses said. "We're really not even setting the schedules today. There's still a whole lot of short-term work that has to be done."
The plan is to remove and replace the box, but that work and related testing will take several days to complete, according to Moses. Once the new box is installed, the team must verify that it's working properly-at least a two-day process-and perform forensics on the failed box.
NASA also reported that Endeavour's six astronauts have returned to NASA's Johnson Space Center in Houston for a few days of additional training before they report to Kennedy for the next launch attempt, and the crew's families also are going to return home May 2. The launch team is backing out of launch countdown operations.
"Responding to problems is one of the things we do best around here, and the team always likes a good challenge," said Mike Leinbach, shuttle launch director. "I'm sure we're going to be really glad when Endeavour's finally on orbit, but right now, the team is upbeat and ready to execute."
During the 14-day mission, the shuttle's last, Endeavour and its crew will deliver the AMS (Alpha Magnetic Spectrometer) and spare parts, including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre, a two-armed robot that is part of the Mobile Servicing System on the International Space Station.
The AMS is a state-of-the-art, high-energy particle-physics experiment built in Geneva by a collaboration of 16 countries. It will search for clues on what the universe is made of and how it began, as well as the origin of dark matter, anti-matter and strangelets, pulsars, blazers and gamma-ray bursters. And that's just what the scientists know to look for.
Endeavour's missions included the first to include four spacewalks, and then the first to include five. Its STS-67 mission set a length record almost two full days longer than any shuttle mission before it. Its airlock is the only one to have seen three spacewalkers exit through it for a single spacewalk. And in its cargo bay, the first two pieces of the International Space Station were joined together.