Space shuttle Endeavour sits on the launch pad early Wednesday morning June 17, 2009. Racing against... 
(AP Photo)
For the second time in less than a week, a potentially dangerous hydrogen gas leak early Wednesday forced NASA to delay shuttle Endeavour's launch to the international space station, this time until July at the earliest.
Launch officials waited almost an hour after the leak appeared during fueling, trying to fix it through remote commands, before calling off the predawn launch.
The leak occurred in the same place as one that cropped up Saturday, in the hydrogen gas vent line that hooks up to the external fuel tank. A similar problem stalled a shuttle flight three months ago.
"We're going to step back and figure out what the problem is and go fix it," said deputy space shuttle program manager LeRoy Cain. "And then we'll fly as soon as we're ready to safely go do that."
Mission managers had ordered repairs following Saturday's delay. The hookup itself and two seals were replaced. The same repair worked back in March, but engineers never found the cause of the problem.
Launch officials said they were proud of the way the team hustled over the past four days trying to get Endeavour to the 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," said Mike Leinbach, who was serving as assistant launch director for this mission. "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 was a keen disappointment considering that they had just gotten a chance, with the start of fueling, at making the launch. Wednesday morning, the astronauts flew back to Johnson Space Center in Houston.
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