Spacewalk
Expedition 24 Flight Engineers Doug Wheelock (left), an Army colonel, and Tracy Caldwell Dyson work to remove a failed ammonia pump module on the International Space Station's S1 Truss.

Two astronauts, one of whom is an Army colonel, took part in the sixth longest spacewalk in history Saturday as part of an effort to fix an ailing cooling system on the International Space Station.

The next spacewalk to complete the removal of a failed ammonia pump module and installation and activation of a new pump module on the International Space Station's S1 Truss will take place no earlier than Wednesday.

Expedition 24 Flight Engineers Doug Wheelock, an Army colonel, and Tracy Caldwell Dyson completed the first spacewalk to remove and replace the pump module at 3:22 p.m. EDT Saturday.

Saturday's excursion lasted 8 hours, 3 minutes, making it the longest expedition crew spacewalk in history and the sixth longest in human spaceflight history.

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.

Teams on the ground are evaluating the impact of the leak on plans to replace the failed pump, as well as possible fixes for the leak. The completion of the process will most likely require at least two additional spacewalks.

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.

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.

Page last updated Fri July 22nd, 2011 at 12:16