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Station Astronauts Conducting First Pump Replacement Spacewalk

Published by Klaus Schmidt on Sat Dec 21, 2013 2:18 pm via: NASA
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Expedition 38 Flight Engineers Rick Mastracchio and Mike Hopkins are working outside the International Space Station Saturday for the first in a series of spacewalks to replace a degraded ammonia pump module associated with one of the station’s two external cooling loops that keeps both internal and external equipment cool.

During the spacewalk, which began at 7:01 a.m. EST and is slated to last about six and a half hours, the two spacewalkers will focus on disconnecting a degraded pump module from Loop A of the station’s external Active Thermal Control System to prepare it for its removal and replacement with a spare during a second spacewalk on Monday. If necessary a third spacewalk would occur on Christmas day to finalize the installation of the replacement pump module.

Astronaut Rick Mastracchio works outside the International Space Station during the first of a series of spacewalks to replace a degraded ammonia pump module.  Image Credit: NASA TV

Astronaut Rick Mastracchio works outside the International Space Station during the first of a series of spacewalks to replace a degraded ammonia pump module. Image Credit: NASA TV

After exiting the Quest airlock, Hopkins will make his way out to Saturday’s worksite at center of the Starboard 1 truss segment. Mastracchio meanwhile will attach himself to a foot restraint at the end of the station’s 57-foot robotic arm so that Flight Engineer Koichi Wakata, the robotics operator for the spacewalks, can fly Mastracchio to the worksite.

The two spacewalkers first will spend some time demating four ammonia fluid line “quick disconnects” from the pump module.

Once the four fluid lines are disconnected, Mastracchio and Hopkins will work to attach the fluid lines to a pump module jumper box, which will allow the ammonia to  reach the system’s plumbing in the ammonia and nitrogen tanks to keep it in a liquid phase.

After the spacewalkers have installed a generic thermal cover over the pump module jumper and ammonia fluid lines, Hopkins will demate the pump module’s five electrical connectors.  Hopkins also will open the multilayer insulation covering the spare pump module located on the External Stowage Platform 3 on the starboard truss.

Mastracchio and Hopkins received some special guidance on the spacewalk procedures from NASA astronauts Doug Wheelock and Tracy Caldwell-Dyson, who replaced the ammonia pump at this same location during three Expedition 24 spacewalks in August 2010. Earlier this week, Wheelock and Caldwell-Dyson spent some time in a partial gravity simulator at the Johnson Space Center to create a training video based on the lessons learned during the last pump module replacement.

With six previous spacewalks under his belt, Mastracchio is serving as the lead spacewalker, or EV1, for Saturday’s excursion.  He is wearing the suit marked with red stripes. Hopkins, who is making his first spacewalk, is designated EV2.  He is wearing the spacesuit with no stripes.

Saturday’s spacewalk is the 175th in support of space station assembly and maintenance.

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