Space station may need emergency spacewalk if software patch fails

A faulty pump means the space station might have to scrap a scheduled resupply to perform an emergency spacewalk. NASA hopes a temporary fix will allow the resupply to go ahead.

NASA engineers appear to have found a way to restore a balky coolant pump on the International Space Station that may allow a station resupply mission to launch this week, as planned.

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The alternative is to delay the launch to allow two ISS crew members to conduct two or three emergency spacewalks starting this weekend to replace the faulty pump.

Spare pumps are stored on the space station's truss scaffolding the length of a football field. The truss supports the station's solar panels, radiators for station cooling, and other utilities, including two external cooling loops that transfer heat to the radiators.

The cooling-system malfunction on the space station occurred Dec. 11. Controllers noticed unusually low temperatures in ammonia circulating through one of the cooling loops. Left unchecked, the chilled coolant could have frozen water flowing through a heat exchanger inside the station.

That could have damaged the exchanger and leaked ammonia into the station, said Judd Frieling, the lead flight director for Expedition 38, the space station's current increment, during a televised update Tuesday.

Controllers were able to reroute cooling to the second external loop, but the transfer meant the crew had to shut down nonessential equipment in order to reduce the heating load on the second loop.

Engineers traced the problem to a malfunctioning valve designed to adjust the flow of coolant. The coolant's temperature should remain within an optimum range for cooling the station's interior and some of its exterior hardware.

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Space station may need emergency spacewalk if software patch fails