ISS Spacewalk 2013: Astronauts Make Rare Christmas Eve Repair To Cooling System
Astronauts aboard the International Space Station made a rare Christmas Eve spacewalk today, repairing a part of the cooling system which began malfunctioning earlier this month. Today's was the second spacewalk within a week, with the spacewalking astronauts working so quickly and effectively that a planned third spacewalk will not be necessary. That's good news for astronauts Rick Mastracchio and Mike Hopkins, who now won't have to spend Christmas day spacewalking.
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The trouble began on December 11, after a cooling system valve stopped functioning. As a result, ISS had to shut down one of two ammonia coolant loops, which led to the shutdown of some of ISS's electronics. (See here for an explanation of ISS's cooling system.) The shutdown rendered ISS astronauts unable to perform certain experiments.
While engineers thought they would be able to fix the problem remotely, that turned out not to be the case, and on Saturday, ISS astronauts performed the first spacewalk. The five-and-a-half hour spacewalk went smoothly--an hour shorter than expected, in fact--and there were no issues with helmet-flooding, something which has been a concern since Luca Parmitano almost drowned in his helmet during a July spacewalk.
During the Saturday spacewalk, astronauts disconnected a 780-pound pump from its ammonia fluid lines, temporarily storing the pump on the outside of the station. During a seven-plus hour followup spacewalk today, astronauts were finished installing and hooking up the new pump just after noon EDT.
Mastracchio and Hopkins only experienced one minor issue during today's spacewalk, when the astronauts had some trouble switching the fluid lines of the cooling system. While prying one of the temporary fluid lines, the astronauts released ammonia. These "snowflakes" got onto the astronauts' spacesuits, preventing Mastracchio and Hopkins from reentering ISS until the toxic chemical "baked out" of their suits.
In 2010, ISS experienced a problem with this same space pump module. It took a series of three spacewalks to fix the pump, with the astronauts running into difficulty while loosening the pump's pressurized lines. Learning from the 2010 incident, the pressure in the lines was reduced in advance of Saturday's spacewalk, allowing the astronauts to more smoothly and quickly complete their task.
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