NASA Performs Critical Space Shuttle Fueling Test

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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