NASA - National Aeronautics and Space Administration

Image above: 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

Flight Engineers Doug Wheelock and Tracy Caldwell Dyson completed the third contingency spacewalk to install a spare ammonia pump module on the S1 Truss at 1:40 p.m. EDT Monday. Flight Engineer Shannon Walker assisted the spacewalkers from inside the International Space Station and operated the Canadarm2.

The 780-pound spare pump module was removed from an external stowage platform by Wheelock while working from the Canadarm2. The module was successfully installed on the S1 Truss after Wheelock attached four bolts and Caldwell Dyson mated five electrical connectors.

Ground controllers confirmed the module was in healthy condition when it began receiving power. After a pressure check and more fluid cable connections, the module was filled with ammonia.

Due to time constraints, ground teams and the crew decided not to attach a power cable extension from Quest to a cable on the Unity module.

Wheelock and Caldwell Dyson were outside during the third repair spacewalk for 7 hours, 20 minutes. On Wednesday they were outside during the second spacewalk for 7 hours, 26 minutes. The first repair spacewalk took place Aug. 7 and lasted a record 8 hours, 3 minutes.

› Read about the Aug. 11 repair spacewalk
› Read about the Aug. 7 repair spacewalk

Plans called for the revived Loop A of the station’s cooling system to be temporarily powered Tuesday after the spacewalk and the spare pump to be shut down temporarily to allow flight controllers to reconfigure systems that have been cooled by Loop B since July 31.

After the original pump module failed July 31 ground controllers powered down numerous station systems and readjusted them to provide maximum redundancy. Mission managers and astronauts on the ground also quickly began choreographing the contingency spacewalks and planning repair procedures. The spacewalks were planned several days apart to give crew members time to rest and managers on the ground time to review data and make necessary adjustments.

The spare ammonia pump installed was delivered aboard space shuttle Discovery and stowed on an external stowage platform in July 2006. STS-121 Mission Specialists Piers Sellers and Mike Fossum performed the transfer work during a 6-hour, 47-minute spacewalk

› 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.