Spacewalkers Remove Failed Ammonia Pump on Station

Crew Conducts Second Spacewalk to Replace Coolant Pump

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 switched their spacesuits to battery power at 8:27 a.m. EDT, signaling the start of the second of three spacewalks focused on removing the ammonia pump module that failed July 31 and putting its replacement in place. Today’s spacewalk is expected to last about six hours.

This is the fifth spacewalk for Wheelock, who is wearing the suit bearing the red stripes, and the second for Caldwell Dyson, who is wearing the unmarked suit.

Wheelock successfully closed the quick disconnect valve for the final fluid connector for the failed ammonia pump module. There are no visible leaks. Then he successfully detached the final fluid line from the failed ammonia pump module.

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 now safely stowed on the truss, Caldwell Dyson is preparing the spare pump for installation on the next spacewalk. Once that task is complete, the spacewalking duo will perform clean up activities before concluding today’s excursion outside the orbiting laboratory.

If all goes as planned, the spare pump will be installed during the third spacewalk targeted for no earlier than Sunday.