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Expedition 24 Performs First Spacewalk to Replace Ammonia Pump
08.07.10
Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson

Expedition 24 Flight Engineers Doug Wheelock (left) and Tracy Caldwell Dyson work to remove a failed ammonia pump module on the International Space Station's S1 Truss. Photo credit: NASA TV

Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson performed the first of three planned spacewalks Aug. 7 to remove and replace an ammonia pump module that failed July 31. The excursion lasted 8 hours, 3 minutes, making it the longest International Space Station-based spacewalk and the sixth longest spacewalk in history.

The repair tasks originally included removing the failed pump module from the station’s S1 Truss and retrieving a spare from an external stowage platform. As the result of an ammonia leak in the final line that needed to be disconnected from the failed pump module, the day’s tasks were only partially completed. The decision was made to reconnect the line on the pump module and install a spool positioning device to maintain proper pressure internal to the ammonia line.

Wheelock conducted the fourth spacewalk of his career. Caldwell Dyson made her first spacewalk. Flight Engineer Shannon Walker operated Canadarm2, the station’s robotic arm, and assisted the spacewalkers from inside the station.

The second spacewalk is scheduled to begin just before 7 a.m. EDT Wednesday, Aug. 11.

After the loss of one of two cooling loops July 31, ground controllers powered down and readjusted numerous systems to provide maximum redundancy aboard the orbiting laboratory. The International Space Station is in a stable configuration, the crew is safe and engineers continue reviewing data from the failed pump.

› View Aug. 2 spacewalk briefing graphics
› View the ISS Active Thermal Control System Overview (1.2 Mb PDF)

Read about the station's Thermal Control System on page 63 of the "Systems" section of the Reference Guide to the International Space Station. View the entire guide here.