Nasa postpones space station mission

WASHINGTON-The Nasa on Tuesday postponed a cargo mission to the International Space Station and instead scheduled three spacewalks so that astronauts can fix a broken cooling system at the research outpost. The decision means that Orbital Sciences’ first regular supply-ship mission to the ISS will be put off until next year.
Instead, a pair of US astronauts will embark on three spacewalks that culminate on Christmas Day, in order to fix the week-old equipment breakdown. “NASA astronauts Rick Mastracchio and Mike Hopkins will remove a pump module that has a failed valve,” NASA said in a statement. “They will replace it with an existing spare that is stored on an external stowage platform.” On December 11, a faulty valve caused a breakdown in one of the station’s two external cooling loops, which circulate ammonia outside the station to keep both internal and external equipment cool, the US space agency said.
Attempts to fix the problem from the ground were apparently not enough to allow the Orbital mission to berth at the research outpost to unload supplies. NASA said the three spacewalks are scheduled for December 21, 23 and 25. The six-man crew was never in danger due to the problem, but NASA has said it would like the system fixed for good, and soon. That means Orbital Sciences’ privately owned cargo ship will have to wait for 2014 to start its journey on its first regular commercial mission to supply the orbiting outpost. The company did a demonstration launch and berthing at the ISS in September, showing it was capable of the mission and paving the way for more supply trips.

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