August 16, 2010

Astronauts Restore Life To Failed Cooling System

Space station astronauts have completed the third spacewalk to install a new pump to restore their cooling system back to full strength for the first time in two weeks.

Douglas Wheelock and Tracy Caldwell Dyson spent over six hours installing the new ammonia pump during the spacewalk.  The astronauts removed the faulty pump during the second spacewalk on August 11.

The International Space Station's (ISS) cooling system stopped running in full power since July 31 when an electrical short shut down one of two pumps that move liquid ammonia through the system.

The third spacewalk kicked off on Monday at 6:20 a.m. EDT, which was about 35 minutes ahead of time.

The astronauts removed the new pump from a spare parts platform on the station's exterior.

"You know, when you're on the [spare parts platform] looking down at the Earth like this, it's like extreme hang gliding," Caldwell Dyson said.

Wheelock faced a little trouble trying to secure one of the four bolts into place on the new pump.

"Come on now, bolt," Wheelock said as he freed the stuck bolt. "Turning! Sweet!"

Wheelock and Dyson completely hooked up the new pump during the third spacewalk, and now only one more spacewalk remains during which the two astronauts will move the disabled pump to its final storage location.

The ISS contains two main cooling system loops: Loop A and Loop B.  The failed pump is in Loop A, while Loop B still remains operational. 

Now only three spare ammonia pumps remain on the space station.  Each pump weighs 780 pounds and is 5 1/2 feet long by 4 feet wide.


Image Caption: Flight Engineers Tracy Caldwell Dyson (left) and Doug Wheelock work to set up the ammonia spare pump module after it was installed on the S1 Truss. Credit: NASA TV


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