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Astronauts Successfully Remove Failed Pump on International Space Station


Expedition 24 Flight Engineers Doug Wheelock (r) and Tracy Caldwell Dyson work to replace a failed ammonia pump module outside of the International Space Station, 11 Aug 2010

Expedition 24 Flight Engineers Doug Wheelock (r) and Tracy Caldwell Dyson work to replace a failed ammonia pump module outside of the International Space Station, 11 Aug 2010

NASA astronauts successfully completed the second of at least three planned spacewalks in an effort to replace a faulty ammonia pump module on the International Space Station's truss. Wednesday's spacewalk clocked in at nearly 7.5 hours, about 40 minutes shorter than the mission's troublesome first spacewalk Saturday.

It has already taken 15.5 hours in spacewalking time and two spacewalking missions for astronauts to remove the failed cooling pump in an effort to bring the ISS back to full capacity.

And the work is not over yet.

Back at Johnson Space Center in Houston, Texas, Space Station Program Manager Michael Suffredini told reporters that Wednesday's spacewalk, or EVA (extravehicular activity), was very successful.

"The hardware cooperated with us in some instances," said Michael Suffredini. "We had a struggle or two in others. But, overall, we got ahead of the timeline and got a few of our 'get-ahead tasks' done in preparation for installing the new pump during EVA Three."

During Wednesday's spacewalk, astronauts had to grapple with the failed module's ammonia-filled hoses, electrical and data cables, as well as a jammed bolt.

Ultimately, NASA says the astronauts were able to remove the faulty 350-kilogram ammonia pump module and complete all the tasks they had planned for the day's mission.

Suffredini said a third spacewalk is now planned for Monday, and a fourth spacewalk likely will be needed to put the old pump into its storage place.

Spacewalking astronauts Doug Wheelock and Tracy Caldwell Dyson, and fellow astronaut Shannon Walker, are working to replace a pump that failed July 31. That pump is supposed to feed ammonia into cooling loops to maintain the proper temperature for the station's electrical and flight systems. When it failed, it took down half of the space station's cooling system.

For the past week and a half, the space station has been operating at half its usual cooling capacity, forcing the astronauts to power down equipment to prevent overheating on the ISS.

NASA says space station's six crew members are not in danger, and that the pump needs to be replaced in the unlikely event that the other working pump fails.

Before Wednesday's spacewalk, the ground control team reduced the pressure in the failed module's ammonia lines, making the task of removing the tubes easier for the astronauts. It was the pressurized ammonia hoses that caused some problems during the first spacewalk of the repair mission, when the astronauts had to deal with an ammonia leak. That spacewalk clocked in at more than eight hours - one of the longest spacewalks in history.

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