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Hydrogen valve in Discovery scrubs tonight's launch
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: August 25, 2009


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Trouble with a critical hydrogen fill-and-drain valve in the shuttle Discovery's aft engine compartment forced NASA managers to call off an attempt to launch the orbiter early Wednesday on a space station resupply mission. It was the second delay in a row for Discovery following a weather scrub earlier Tuesday.

"We have scrubbed for the evening, officially at 5:52 p.m. Eastern," said launch commentator Allard Beutel. "The last half an hour or so, a problem cropped up with a fill-and-drain valve in the bottom part of the shuttle, the aft part of the shuttle, related to the liquid hydrogen. This particular valve ... gave indications it did not close when it was commanded to."

It was not immediately clear what might be needed to replace the valve or restore it to normal operation.

But NASA only has until Aug. 30 to get Discovery off the ground or the flight will be delayed to mid October because of upcoming Japanese and Russian space station missions and a conflict with the Air Force Eastern Range, which provides tracking and telemetry support for all rockets launched from Florida.

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With a 70 percent chance of good weather expected, engineers began fueling Discovery at 3:45 p.m., setting up a launch attempt at 1:10:22 a.m. Wednesday. But just before 6 p.m., engineers stopped loading liquid hydrogen when an inboard fill-and-drain valve appeared to malfunction.

"You have to have it closed for flight," said Beutel. "You don't want it to get stuck in the position where it's closed because you cannot drain the tank that way (after a delay). The Launch Director Pete Nickolenko has given the team's the direction to stop the fill of liquid hydrogen, so they have, and there are discussions going on now with the team and space shuttle launch management."

He said engineers were no sure of the exact state of the inboard hydrogen fill-and-drain valve.

"This is not one of those valves that allows (cycling) because you don't want to have it in a position of broken/closed," he said. "So with that, the liquid hydrogen filling of the external tank has stopped."

Additional details will be posted as they become available.

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