Last week, one of the International Space Station's two coolant loops shut down, forcing the six astronauts on board to turn off all nonessential equipment. Two American astronauts — Rick Mastracchio and Michael Hopkins — will be leaving the confines of the ISS on Saturday, Monday, and Christmas Day, to replace a malfunctioning valve. The timing of the spacewalks means that the scheduled launch of Orbital Sciences' Cygnus mission has been delayed until January 13th at the earliest. Cygnus — a cargo ship carrying supplies to the ISS — was set for this week, the ship using its Antares rocket to blast off from Virginia before docking with the space station.
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NASA to fix ISS coolant system with Christmas spacewalks