CAPE CANAVERAL, Fla. -- An abrupt and puzzling leak in the astronauts' oxygen supply forced NASA to delay Monday's planned launch of space shuttle Endeavour by at least one week.
With just two hours remaining in the countdown Sunday night, NASA called off the flight to the international space station and apologized to the seven-member crew.
Commander James Wetherbee had just strapped into his cockpit seat.
"I'd like to welcome you aboard ... but tonight's not our night," NASA test director Steve Altemus said. "I know you guys are going to be disappointed, but I think we want to give you a healthy vehicle before we cut you loose from the cape here."
Wetherbee replied: "Absolutely."
The oxygen leak is believed to be somewhere deep in the midbody of Endeavour beneath the payload bay. It is in one of two systems that feed oxygen into the crew cabin for breathing and into the astronauts' pressure suits during launch and landing.
Launch controllers had just begun fueling Endeavour for an early Monday morning launch when they detected the leak. It was a stunning discovery since both oxygen lines had passed all inspections back in the hangar.
The concern was that the leak, while small, could worsen. It was the latest in a series of problems that have plagued NASA's shuttles this year, most notably fuel line cracks that grounded the entire fleet all summer.
"It's like this leak just appeared out of the blue," said shuttle program director Ron Dittemore. "For that alone and knowing that you still have the shake, rattle and roll to go through to get to orbit, caused us to pause and want us to understand it better."
Dittemore said the oxygen systems are redundant and NASA probably could have launched Endeavour without any issues. But he noted: "It's the unknown, why this happened after it passed the checks. Did we have some collateral damage? Is it worse? ... We just couldn't go and launch in the blind."
Endeavour was poised to carry up a fresh three-man crew to replace the current space station occupants, who have been on board since June. The shuttle also holds a $390 million girder for the orbiting complex.
Launch director Mike Leinbach said Endeavour's payload bay doors will be opened and even though it will be a tight squeeze for workers to find and fix the leak, the 14-ton girder should not have to be removed. The problem could be a loose seal or tube fitting, he noted.
The launch was rescheduled for no earlier than Nov. 18.
Mission Control immediately notified the one American and two Russian space station residents about the delay in Endeavour's launch -- and their ride home. Sunday was their 158th day in orbit.
Peggy Whitson and her cosmonaut crewmates were supposed to return to Earth last month. But their mission was extended because of the summerlong grounding of the shuttle fleet.
Cracks in the fuel lines of all four shuttles resulted in a launch moratorium that did not end until last month.
Then when Atlantis finally lifted off on Oct. 7, half of the explosive charges for releasing bolts that hold the shuttle onto the pad did not fire. Fortunately, only one set of explosives is needed for release; the other set serves as a backup.
Even though engineers could not determine what caused the electrical failure, NASA pressed ahead with Endeavour's launch, saying the problem was almost certainly an isolated event. Nevertheless, the wiring for Endeavour's explosive charges were double-checked and, in some cases, replaced.
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