Spacewalkers remove railed ammonia pump on space station

08:23, August 12, 2010      

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Spacewalkers Tracy Caldwell Dyson (L) and Doug Wheelock, attached to the International Space Station's robot arm, work to replace the failed ammonia coolant pump module on the station's S1 truss in this image from NASA TV August 11, 2010.(Xinhua/Reuters Photo)

Two U.S. astronauts aboard the International Space Station have completed the second of three spacewalks to remove the 780-pound failed ammonia coolant pump module on the station, the U.S. National Aeronautics and Space Administration (NASA) said on Wednesday.

The spacewalk, conducted by Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson, ended at 3:53 p.m. EDT Wednesday.

Wheelock successfully closed the quick disconnect valve for the final fluid connector for the failed ammonia pump module. Then he successfully detached the final fluid line from the module.

Caldwell Dyson disconnected five electrical and data cables while Wheelock broke torque and removed four bolts from the old pump. The pump module then was extracted from the truss through the use of a grapple bar and installed on a payload bracket on the Mobile Base System on the station's truss.

With the failed pump module safely stowed on the truss, Caldwell Dyson prepared the spare pump for installation on the next spacewalk targeted for no earlier than Sunday.

The space station has been operating with only half its usual cooling capability since the ammonia coolant pump failed on July 31. Science research is on hold and unnecessary equipment is off until the pump can be replaced. The cooling system is crucial for keeping electronics from overheating.

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