Doug Wheelock & Tracy Caldwell Dyson Wrap Up First Spacewalk to Replace Ammonia Pump

August 9, 2010

As the result of an ammonia leak in the final line that needed to be disconnected, teams decided to reconnect the line on the pump module and install a spool positioning device to maintain proper pressure internal to the ammonia line. At this point Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson will wrap up today's spacewalking tasks. The spacewalkers will “bake-out” any residual ammonia flakes that escaped from the lines. In the U.S. Quest airlock, they also will cleanse any additional ammonia.

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. Credit: NASA TV

Teams will evaluate the go forward plan for the second planned spacewalk.

Wheelock and Caldwell Dyson are conducting the first of two spacewalks to remove and replace an ammonia pump module that failed July 31. Their spacewalk began at 7:19 a.m. EDT when the two astronauts switched their spacesuits to internal battery power.

Wheelock, designated as EV1, or extravehicular crew member 1, is wearing the spacesuit bearing the red stripes and conducting the fourth spacewalk of his career. Caldwell Dyson, designated as EV2, is wearing the unmarked spacesuit and making her first spacewalk. Flight Engineer Shannon Walker is operating Canadarm2, the station’s robotic arm, and assisting the spacewalkers from inside the station.

Approximately two hours after the conclusion of the spacewalk NASA TV will broadcast a briefing from Johnson Space Center. The briefing participants will include Mike Suffredini, International Space Station program manager; Courtenay McMillan, Expedition 24 spacewalk flight director; and David Beaver, Expedition 24 spacewalk officer.

The first spacewalk was originally planned for Friday morning, but mission managers decided an additional day was necessary to finish working out all the spacewalk details. The additional time allowed for the final procedures to be uplinked to the station crew late Thursday and gave the crew one full day to review the plans that were developed by teams of flight controllers, engineers, and spacewalk and robotics experts. Managers also moved the second spacewalk to Wednesday to give the crew additional time to rest and prepare.

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.