This story was updated at 3:52 p.m. EDT.
NASA will
fuel up the space shuttle Endeavour's massive external tank next week to check
repairs aimed at stopping a hydrogen gas leak that has twice delayed the
spacecraft's launch.
Set for
Wednesday, the so-called "tanking test" will fill Endeavour's attached 15-story
fuel tank with the 526,000 gallons of super-cold liquid hydrogen and liquid
oxygen propellant needed to launch
a shuttle into orbit. During two launch attempts this month, an excessive
leak of hydrogen gas from the fuel tank forced NASA to stand down during the
fueling process. The shuttle is now slated to launch no earlier than July 11.
It takes
about three hours to fuel a shuttle external tank, during which time some of
the cryogenic liquid hydrogen boils off and must be vented away from the launch
pad and safely burned off to avoid an explosion
risk. NASA engineers believe a misalignment in a Teflon seal between the
vent line and Endeavour's external tank allowed some of the flammable hydrogen
gas to leak out during launch attempts on June 13 and June 17 at the Kennedy
Space Center in Cape Canaveral, Fla.
"They think
they have a pretty good handle on what they think caused the leak," NASA spokesperson Candrea Thomas told SPACE.com from
the Florida spaceport. "The tanking
test will tell, but hey're confident they've got this thing figured out."
Engineers
are working to install a new Teflon seal and special washers to fill in the gap
caused by the misalignment, Thomas said.
Endeavour
and its seven-astronaut
crew are poised to launch an ambitious 16-day mission to the International
Space Station to deliver the final piece of the outpost's $1 billion Kibo
Japanese laboratory. The astronauts plan to attach a porch-like external experiment
platform to Kibo and perform five daunting spacewalks during the flight.
The shuttle
is currently scheduled to launch on July 11 at 7:39 p.m. EDT (2339 GMT), but
could launch anytime through July 14. If the shuttle cannot launch by then, it
would have to wait until July 27 to allow a previously scheduled unmanned Russian
cargo ship to dock
at the station. That Progress freighter is due to launch from the Central
Asian spaceport of Baikonur Cosmodrome in Kazakhstan on July 24 and arrive at
the station a few days later.
NASA plans
to begin next week's fueling test for Endeavour at about 7:00 a.m. EDT (1100
GMT) on Wednesday, Thomas said. The test will be broadcast live on NASA TV, she
added.
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