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NASA astronauts fail attempt to fix space station cooling system

In this image taken from video and made available by NASA astronaut Doug Wheelock, foreground begins the first of two spacewalks to replace a broken ammonia pump Saturday Aug. 7, 2010. (AP Photo/NASA)
In this image taken from video and made available by NASA astronaut Doug Wheelock, foreground begins the first of two spacewalks to replace a broken ammonia pump Saturday Aug. 7, 2010. (AP Photo/NASA) (Anonymous - AP)

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By Marcia Dunn
Sunday, August 8, 2010

CAPE CANAVERAL, FLA. -- A pair of NASA astronauts ventured outside the International Space Station on Saturday to repair a faulty cooling system but ran out of time before they could remove a pump that broke last weekend.

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Douglas Wheelock and Tracy Caldwell Dyson were attempting to swap in a spare to replace the faulty ammonia coolant pump. The job was considered so difficult -- one of the most challenging repairs ever attempted at the orbiting lab -- that NASA planned two spacewalks, the first on Saturday. So little progress was made that NASA later said a third would be necessary.

Wheelock and Caldwell Dyson disconnected three pressurized ammonia hoses from the disabled pump but were unable to remove the last hose.

"Wow. That thing is not budging," Wheelock told Mission Control at one point.

Lagging well behind schedule, Wheelock finally succeeded in dislodging the balky line by banging a jammed button with a special tool.

Mission Control erupted in applause. "Awesome," Mission Control radioed up.

But the exuberance was dampened by a stream of escaping ammonia that resembled tiny snowflakes. "It's got a pretty good snowstorm there," Wheelock reported.

The astronauts managed to stop the leak when they plugged the troublesome connector back in. There was time for little else as the spacewalk neared the seven-hour mark. They headed back to the air lock, where they had to go through decontamination procedures, stretching the spacewalk to eight hours and three minutes. NASA said it was the sixth-longest spacewalk ever.

The ammonia pump shut down last weekend and knocked out half of the space station's cooling system. The pump is supposed to push ammonia coolant through the lines on the right side of the complex and prevent equipment from overheating. To cope with the failure, the six-person crew had to turn off all unnecessary equipment and halt science experiments.

The cooling line on the left side -- unaffected by the trouble -- has had to manage everything.

Engineers worked nonstop over the past week to come up with the emergency repair plan. Astronauts in Houston rehearsed the spacewalk while submerged in NASA's huge training pool.

Although space station managers knew an ammonia pump would fail one day, they did not expect it to happen so soon in the 12-year life of the complex. The broken pump had been in operation since 2006.

Each pump is about the size of a bathtub and weighs 780 pounds. Astronauts will attempt to install the new pump, an on-board spare, on the second spacewalk, which is planned for Wednesday.

NASA said the breakdown is serious but has not endangered the crew, and the one functional cooling loop has kept the space station stable. Additional breakdowns could leave the station in a precarious situation, however, and that's why managers wanted to get the broken line working again as soon as possible.

-- Associated Press


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