NASA plans 3 spacewalks to fix space station glitch

Project to fix broken pump module forces NASA to postpone launch of Cygnus resupply mission

NASA has postponed the launch of a mission to resupply the International Space Station so it can focus on undertaking three spacewalks to fix a glitch in the orbiter's cooling system.

The space agency said the glitch poses no danger to the space station crew or the scientific experiments being done there, but they want to get it fixed as soon as possible.

The problems surfaced on Wednesday, Dec. 11, when the pump module on one of the space station's two external cooling loops shut down after reaching a pre-set temperature limit. The loops are used to circulate ammonia, a coolant, outside of the orbiter to keep the internal and external equipment cool.

Engineers suspect the problem is a malfunctioning flow control valve inside the pump.

When the trouble first arose, the ground team moved some electrical systems from the problematic loop to a second one. They also powered down some non-critical systems inside the Harmony node and two laboratories to lighten the cooling load on the station.

Last weekend, NASA engineers on the ground worked to regulate the temperature in the cooling loop, but the remote efforts didn't fix the problem.

In the latest effort, NASA said astronauts Rick Mastracchio and Mike Hopkins are scheduled to work on the malfunctioning pump during spacewalks on Dec. 21, 23 and 25. Each of the planned spacewalks are scheduled to begin at 7:10 a.m. ET, last six and a half hours. Each will be shown live on NASA TV.

During the spacewalk, Mastracchio and Hopkins will work to remove the pump module and replace it with a spare now stowed on an external platform.

Due to the repair project, NASA postponed the launch of Orbital Sciences' Cygnus cargo spacecraft that was set to carry supplies to the space station. The launch will now come in mid-January at the earliest.

Sharon Gaudin covers the Internet and Web 2.0, emerging technologies, and desktop and laptop chips for Computerworld. Follow Sharon on Twitter at @sgaudin, or subscribe to Sharon's RSS feed . Her email address is

Copyright © 2013 IDG Communications, Inc.

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