Analysis, Spacewalk Preparations Continue After Loss of Cooling Loop on Space Station

Analysis, Spacewalk Preparations Continue After Loss of Cooling Loop
Teams of flight controllers are continuing engineering analysis and refining procedures to replace a failed International spacewalkSpace Station ammonia pump module later this week. Expedition 24 astronauts Doug Wheelock and Tracy Caldwell Dyson currently are scheduled to start the repairs on the station’s starboard truss Thursday.

A briefing to discuss the current station status and to preview the upcoming spacewalks will be broadcast on NASA Television at 4 p.m. EDT today. Briefers will include Michael Suffredini, the International Space Station Program Manager, and Flight Director Courtenay McMillan, who will lead the team supporting the spacewalks.

The pump failed Saturday night after a spike in electrical current tripped a circuit breaker. When the 780-pound pump failed, it shut down half of the station’s cooling system. Efforts to restart the pump, which feeds ammonia coolant into the cooling loops to maintain the proper temperature for the station’s electrical systems and avionics, were not successful. The station’s crew worked with Mission Control to put the station in a stable configuration. The crew, which is in no danger, has resumed normal work activities. A tag-up to review procedures with spacewalk specialists is planned later today.

On Wednesday, flight controllers plan to move the Mobile Transporter, which will be used to support robotics operations for the spacewalks, into position at the replacement worksite.

Current planning continues to support an initial spacewalk on Thursday beginning just before 7 a.m. by Wheelock and Caldwell Dyson to unbolt and remove the failed pump module, and to install the spare. NASA TV coverage will begin at 6 a.m. A second spacewalk to hook up a variety of electrical and fluid connections for the new pump module could occur two or three days after the first spacewalk.

Wheelock, who will be designated as EV1, or extravehicular crew member 1, wearing the spacesuit bearing the red stripes, will be making the fourth spacewalk of his career, while Caldwell Dyson, designated as EV2, wearing the unmarked spacesuit, will be making her first spacewalk.

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