NASA cancels Endeavour launch due to another hydrogen leak

CAPE CANAVERAL, Florida -- For the second time in less a week, a hydrogen gas leak on shuttle Endeavour's fuel tank early Wednesday forced a launch delay, pushing its space station construction mission into July.

NASA waited almost an hour after the leak appeared, trying to fix it through remote commands, before calling off the predawn launch attempt.

Launch officials said the leak occurred in the same place as one that cropped up Saturday during fueling, in the hydrogen gas vent line that hooks up to the external fuel tank.

On Wednesday, engineers opened and closed a valve in hopes of stopping the leakage or, at the very least, better understanding it. But that did not work and the countdown was halted just 3 1/2 hours before the scheduled launch time.

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

Mission managers had ordered repairs following Saturday's delay. 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.

The latest leak occurred a little earlier in the fueling, said Mike Leinbach, assistant launch director for the mission.

Leinbach said he was proud of the way his team hustled over the past four days trying to get Endeavour to the international space station, with a new outdoor addition for the Japanese lab.

"I sure wish we could have rewarded them and the astronauts and everybody else with a launch this morning," he said. "But the leak was way out of spec again, and so we were just not comfortable pressing on."

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.