Usually, a hitch encountered while fixing an air conditioner doesn't make the news--except when that AC orbits 220 miles above the earth, requires astronaut mechanics, and remains inoperable after the sixth longest spacewalk in history. Last week, we discussed a broken ammonia cooling loop--one of two keeping the International Space Station air-conditioned and habitable. Though the second loop is keeping the six astronauts aboard comfortable, they prefer to be more than mishap away from a 500 degree Fahrenheit temperature difference across their orbiting laboratory. Now, following Saturday's eight-hour spacewalk, the cooling loop is closer to repair but will require two additional walks. The next will occur no earlier than Wednesday, a NASA press release says. NASA had announced previously that the repair would take multiple walks. The astronauts originally planned to remove four coolant lines on Saturday, a necessary step before removing and replacing a broken pump. This spacewalk ran into trouble with the second line's fitting--which jammed. Said Michael T. Suffredini at the Johnson Space Center in Houston:
“Ammonia QDs are known to be sensitive systems,” he said referring to the quick-disconnect fittings. “They’re very complicated; it’s very high-pressure ammonia you have to try to be able to disconnect and reconnect on a regular basis.... We will get through this problem,” he said. “The challenge is to get through this problem before the next problem hits the other cooling system.” [The New York Times]
The pair of astronauts on the walk, Doug Wheelock and Tracy Caldwell Dyson, moved on to the remaining lines which they successfully removed before doubling back to the second. They successfully removed the line but noticed ammonia ice crystals--a leak. Mission Control in Houston instructed the astronauts not to attach the line to a "bypass mechanism," so they reattached it to the fitting before ending the walk to plan for the next attempt.
Because of the leak, the spacewalkers spent extra time in the airlock to flush out any ammonia that may have attached to their spacesuits. The decontamination procedure is routine whenever spacewalkers are exposed to free-flying ammonia, which can be a hazard if it gets into the space station's air. [ABC News]
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Image: NASA TV