NASA to Check Space Shuttle Fix With Fueling Test

by Tariq Malik, Senior Editor

Date: 25 June 2009 Time: 03:15 PM ET

NASA Delays Moon Mission for Wednesday Shuttle Launch

On Launch Pad 39A at NASA's Kennedy Space Center in Florida, workers prepare to remove the seal from the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A leak of hydrogen at this location during tanking June 12 for the STS-127 mission caused the mission to be scrubbed at 12:26 a.m. June 13.
CREDIT: NASA/Tim Jacobs

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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