This
story was updated at 10:38 a.m. EDT.
NASA fueled
the space shuttle Endeavour early Wednesday in an apparently successful test of
repairs aimed at eliminating a potentially dangerous hydrogen gas leak.
During the
test at the Kennedy Space Center in Florida, NASA loaded Endeavour's massive
external tank with super-chilled liquid hydrogen and liquid oxygen while
watching a hydrogen gas vent line for excessive
leaks. But after filling the 15-story tank with 526,000 gallons of propellant,
no abnormal leaks were detected, boosting confidence that Endeavour will
be ready for a July 11 launch.
"We think
we've got this licked," said NASA test director Steve Payne during the fueling
test. "This should solve it, and the test we're doing today is to verify it
before we go launch next week."
The
hydrogen gas leak prevented NASA from launching Endeavour during two
consecutive attempts on June 13 and June 17. After the second try, NASA
stood down to study the leak in more detail and allow an unmanned rocket to
launch a pair of new U.S. moon probes.
Shuttle
engineers traced the flammable gas leak to a misaligned plate linking Endeavour's
fuel tank with a Teflon seal and vent line that carries excess hydrogen away
from the launch pad. During fueling, a shuttle's cryogenic liquid hydrogen
propellant boils off over time, so the resulting flammable gas must be vented
to a nearby flame stack to be burned off safely. An excessive leak of hydrogen
gas at the launch pad could pose an explosion risk during liftoff.
"Preliminary
results indicate that repairs to the ground umbilical carrier plate, or GUCP,
were successful," NASA spokesperson Candrea Thomas said as the fueling test
concluded.
NASA will
update the public and reporters on the results of today's test later today
during a televised briefing at 1:00 p.m. EDT (1700 GMT).
Leak
repairs
To plug Endeavour's
hydrogen gas leak, NASA engineers replaced the single-piece Teflon seal with a
two-piece version and attempted to fix the misalignment with special
washer-like shims. Payne said shuttle engineers worked through weekends and
around the clock, when weather permitted, to repair Endeavour in time for
today's test.
NASA began
pumping Endeavour full of fuel at 6:48 a.m. EDT (1100 GMT) at its seaside
launch pad in Cape Canaveral, Fla. By about 9:00 a.m. EDT (1300 GMT), the tank was
about 98 percent full with no indications of a hydrogen as leak.
NASA
spokesperson Kyle Herring said the test results are encouraging, but a final
inspection of the fuel tank by engineers must be completed first.
"We've
passed the point where we've had problems before, and once you've done that you
typically don't see leaks, historically," Herring told SPACE.com. "I'd say we're
cautiously optimistic at this point."
Endeavour
is currently slated to launch at 7:39 p.m. EDT (2339 GMT) on July 11 to begin a
planned 16-day mission to the International Space Station. The shuttle's seven-astronaut
crew plans to deliver the last piece of the station's massive
Japanese lab Kibo, perform five rigorous spacewalks and replace one member
of the outpost's six-man crew during the marathon spaceflight.
The mission
has until July 14 to launch before NASA would have to stand down until July 27
so a previously scheduled unmanned Russian cargo ship can launch and dock at
the space station, mission managers have said.
Stuck
knob freed
While
today's fueling test was performed on Endeavour, another team of engineers is
inspecting a flight deck window on the shuttle Atlantis, which flew a
successful mission to the Hubble Space Telescope in May.
A work
light knob had inadvertently
wedged itself between the window and shuttle dashboard while Atlantis was
in space, forcing engineers on Earth to pressurize the orbiter's cabin to
expand it slightly in order to remove the part. A team will inspect the window
for damage to determine if needs repairs or replacement.
Atlantis is
slated to launch supplies to the International Space Station on Nov. 12.
NASA
will update the public and media on the results of today's fueling test aboard
Endeavour at 1:00 p.m. EDT (1700 GMT) on NASA TV. Click here for
SPACE.com's live shuttle mission updates and a link to NASA TV.
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