Flight Engineers Rick Mastracchio and Mike Hopkins continue preparing for a series of spacewalks to remove a failed pump module and install a spare pump module. NASA managers have planned for the first spacewalk to begin Saturday, the second on Monday and if necessary a third spacewalk on Christmas day.
Station Program Manager Mike Suffredini, Flight Director Dina Contella and lead spacewalk manager Allison Bolinger provided more details during a spacewalk briefing at Johnson Space Center.

NASA managers are evaluating whether to go for a Dec. 19 launch of Orbital Sciences’ Cygnus commercial resupply craft or move ahead with a series of spacewalks to repair a pump that is part of a cooling loop that shutdown last Wednesday due to low temperatures seen in the line.

Ground controllers have been sending commands to another valve that is part of the station’s cooling system. The hope is that this valve can be positioned in a way to help maintain the proper temperature in the loop, which could allow them to reintegrate part of the station’s internal electronics.

Earlier Wednesday, the pump module on one of the space station’s two external cooling loops automatically shut down when it reached pre-set temperature limits. These loops circulate ammonia outside the station to keep both internal and external equipment cool. The flight control teams worked to get the cooling loop back up and running, and they suspect a flow control valve actually inside the pump module itself might not be functioning correctly.