Expedition 24 flight engineers Doug Wheelock and Tracy Caldwell Dyson switched their spacesuits to battery power at 7:27 a.m. CDT Wednesday, signaling the start of today's spacewalk, the second of at least three spacewalks focused on removing and replacing a pump module that failed on July 31. Today's spacewalk is expected to last about six hours.
This is the fifth spacewalk for Wheelock, who is wearing a spacesuit bearing red stripes, and the second for Caldwell Dyson, whose suit is unmarked.
After setting up tools and moving to their worksite, the spacewalkers will first isolate the Loop A cooling line, closing quick disconnect lines, and then will use a tool to vent residual ammonia before proceeding to disconnect the M3 fourth and final umbilical they left mated during the first spacewalk.
They will then demate five electrical and data cables and loosen four bolts from the old pump so that it can be extracted and parked on a payload bracket on the station's mobile base system.
If all goes as planned, the spare pump will be installed during the third spacewalk targeted for no earlier than Sunday.