Hydrogen gas leaks again from space shuttle vent line during fueling, launch delay likely

Hydrogen gas leaks again from shuttle vent line

CAPE CANAVERAL, Fla. — For the second time in under a week, hydrogen gas leaked from a vent line on space shuttle Endeavour’s external fuel tank Wednesday and threatened to push the launch into July.

NASA did not immediately call off Wednesday morning’s launch attempt. But it appeared unlikely the shuttle would be able to take off on its space station construction mission.

Launch officials said the leak occurred in the same place as one that cropped up Saturday during fueling and caused a four-day launch delay. Engineers opened and closed a valve in hopes of stopping the leakage or, at the very least, better understanding it.

The leak seemed to have different characteristics this time, launch commentator Mike Curie said.

Mission managers had ordered repairs to the hydrogen gas vent line hookup following Saturday’s delay. In fact, the hookup itself and two seals were replaced. The same repair worked back in March, when a similar leak stalled a shuttle flight. Engineers, however, never found the cause of the problem.

Even before hydrogen gas began leaking — a serious situation because of its flammability — NASA was up against a tight deadline for making the 5:40 a.m. launch. Fueling was delayed three hours by thunderstorms Tuesday night, and the launch team was racing against the clock to catch up.

The seven astronauts were still in crew quarters when the leak was detected. It came as a blow considering that they had just gotten a chance, with the start of fueling, at making the launch.

NASA bumped an unmanned moon shot — its first in a decade — to give Endeavour this second chance of flying before a thermal blackout period kicks in.

That moon mission, featuring two science probes, is now scheduled for a Friday launch. After Saturday, unfavorable sun angles prevent Endeavour from taking off before July 11.

Whenever Endeavour flies, it’s set to deliver the third and last segment of Japan’s massive space station lab. It will be one of the longer international space station visits — nearly two weeks docked at the orbiting outpost — and include five spacewalks.

Once the shuttle pulls up at the space station, there will be 13 people together in space for the first time ever.

A delay until July would push back the next few shuttle flights.

NASA is up against a 2010 deadline for carrying out its final eight shuttle flights, all of them trips to the space station. The White House wants the three remaining shuttles retired and the space station completed by the end of next year.

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NASA: spaceflight.nasa.gov