Feature

Text Size

Expedition 24 Performs Second Spacewalk to Replace Ammonia Pump
08.11.10
Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson

Image above: Expedition 24 Flight Engineers Doug Wheelock (right) and Tracy Caldwell Dyson work to replace a failed ammonia pump module outside of the International Space Station. Credit: NASA TV

Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson have completed the second of three spacewalks to remove the failed ammonia coolant Pump Module on the S1 truss of the International Space Station that failed July 31. Their seven-hour, 26-minute spacewalk ended Aug. 11 at 3:53 p.m. EDT.

Wheelock successfully closed the quick disconnect valve for the final fluid connector for the failed ammonia pump module. Then he successfully detached the final fluid line.

Caldwell Dyson disconnected five electrical and data cables while Wheelock broke torque and removed four bolts from the old pump. The pump module then was extracted from the truss through the use of a grapple bar and installed on a payload bracket on the Mobile Base System on the station’s truss.

With the failed pump module safely stowed on the truss, Caldwell Dyson prepared the spare pump for installation on the next spacewalk targeted for no earlier than Aug. 16. A fourth spacewalk may be required to clean up the work site.

This was the 241st spacewalk conducted by U.S. astronauts, the fifth for Wheelock and the second for Caldwell Dyson. So far, they have spent 15 hours, 29 minutes working on the pump module replacement. It was the 149th in support of International Space Station assembly and maintenance, totaling 937 hours, 4 minutes. It was the 121st spacewalk based out of the space station. Wheelock’s five spacewalks total 36 hours, 10 minutes.

› Read about the first spacewalk to replace failed coolant 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.