UPDATE: A malfunction in a power unit has forced NASA officials to postpone the launch of Endeavour until at last May 2.
NASA officials have postponed the final launch of the space
shuttle Endeavour after discovering a problem with heaters in one
of the vehicle's auxiliary power units.
Endeavour had been scheduled to launch just before 4 p.m. ET,
and had been given the go-ahead earlier April 29. However, the launch
was scrubbed just before 1 p.m. ET after the malfunction was
discovered. NASA officials said the next opportunity to get the shuttle
into space would be May 2.
According to NASA, engineers during countdown detected a failure in
in one of two heater circuits in what the agency calls APU (Auxiliary
Power Unit) 1. Engineers unsuccessfully tried to activate the heater.
Such heaters are used to to keep the APUs' hydrazine from freezing
while in orbit. The APUs reporteldy help power hydraulics for the
shuttle's engines and flaps.
The malfunction made that power unit unusable. Endeavour reportedly
has three APUs, but needs all three functioning before being sent into
According to NASA officials, engineers seem to believe that the
problem has to do with either a load control assembly, which the
agency described as a switchbox found at the aft end of the shuttle, or
an electrical short in the wires leading into or out of the switchbox.
Engineers will drain Endeavour's external tank, NASA said. That will
give them access to the ship's aft compartment overnight, and
eventually they will determine whether the switchbox needs to be
replaced, or faulty wiring fixed.
NASA officials are scheduled to speak at a press conference at 4 p.m. ET to discuss the issue.
The scrubbing of the launch came hours after NASA space shuttle
managers gave a "go" to begin loading shuttle Endeavour's external tank
with more than 500,000 gallons of liquid oxygen and liquid hydrogen,
the space agency reported. The operation is set to begin at 6:22 a.m.,
and with a 70 percent chance of favorable weather for launch, liftoff
is targeted for 3:47 p.m.
The primary weather concern was for low cloud ceilings and
crosswinds at the Shuttle Landing Facility. NASA reported a front would
pass through Kennedy between 7 a.m. and 8 a.m., bringing a chance for
showers. After the front passes, high pressure will build into the area
and winds will shift to the northeast and be near the peak limit for
crosswinds. The Transatlantic Abort Landing site at Istres, France, is
The crew members for space shuttle Endeavour's STS-134 mission are
Commander Mark Kelly, Pilot Gregory H. Johnson and Mission Specialists
Michael Fincke, Greg Chamitoff, Andrew Feustel and European Space
Agency astronaut Roberto Vittori. During the 14-day mission, 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, and extends the function of the system to
replace some activities otherwise requiring spacewalks.
"The AMS is an amazing story all by itself," said Gary Horlacher,
lead space shuttle flight director for the mission. "They've been
working on this for well over 15 years now. It's bigger than a VW bug,
and it will be able to look at things that the other observatories
aren't even looking at. It is, without a doubt, going to continue to
rewrite our future as we try to figure out our past."
The AMS is a state-of-the-art, high-energy particle-physics
experiment built in Geneva by a collaboration of 16 different
countries. It will search for clues on what the universe is made of and
how it began, 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.
"I am quite confident that once we start measuring data in space, we
will find things that we never anticipated," NASA's AMS project manager
Trent Martin said. "And those things will lead to potential new areas
of study, new areas of science and maybe even redefine some of the
After AMS is installed on the station's truss during the fourth day
of the mission, a pallet of spare parts will be added to the space
station on the mission's flight day five. Then there will be a string
of spacewalks-the last spacewalks to be performed by a shuttle
crew-dedicated to getting the station in the best-possible shape for
the end of the space shuttle program.
Among Endeavour's missions was 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.
NOTE: This story was updated to reflect the postponement of the space shuttle launch.