Spacewalkers hunt for leak on International Space Station

Astronauts Thomas Marshburn and Christopher Cassidy are in the middle of a spacewalk to fix an ammonia leak. But after two hours of work Saturday, the astronauts didn't find any evidence of a leak in the pump.

By David Clark Scott,?Staff writer / May 11, 2013

The gloved hands of one of two astronauts working to replace a possible faulty pump on the International Space Station that was leaking ammonia.

NASA screenshot

Enlarge

Two hours into an unplanned spacewalk Saturday morning, the two astronauts have not found the source of ammonia coolant leak on the International Space Station.

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Astronauts Thomas Marshburn and Christopher Cassidy began their spacewalk at 8:44 a.m. Saturday. The two successfully removed a 60-pound pump box which NASA suspected was the source of the leaking ammonia coolant. But they found no evidence of the frozen ammonia flakes that had originally led them to the pump box.

The astronauts also found no evidence of damage to the box.

The walk was hastily planned after ISS crew members alerted Mission Control about the leak on Thursday when they spotted "snowflakes" of frozen ammonia floating near the pump box. NASA says that it has been aware of a slow ammonia leak, but the rate had jump to 5 pounds per day on Thursday.

The ammonia coursing through the plumbing is used to cool the space station's electronic equipment, according to the Associated Press. There are eight of these power channels, and all seven others were operating normally. As a result, life for the six space station residents was pretty much unaffected.

NASA's space station program manager Mike Suffredini said it's a mystery as to why the leak erupted on Thursday. One possibility is a micrometeorite strike.

By 11 a.m. Saturday, Cassidy and Marshburn were working to remove a nearby spare pump and drop it in the location where the suspected pump box was removed. The two men? are experienced spacewalkers: this is their fourth working sojourn outside the space station.

If the pump isn't the source of the leak, NASA's hunt for the source will continue. But that will be another crew's problem. Mashburn and Canadian commander, Chris Hadfield, are scheduled to head back to Earth on Monday.

But as the two men worked, there were the occasional moments when they could pause to look at the view 255 miles above the Earth. "Did you see the moon? Oh my God! Burn that in your memory, said Cassidy.

After running through a system check, the following exchange was heard:

"Houston, if you're still there, I'm feelin great," said Cassidy.

"We're still there. Copy that on feelin great," responded Mike Fincke, an astronaut who was guiding the duo from NASA's Johnson Space Center in Houston.

NASA is broadcasting the spacewalk live on its website.

Source: http://rss.csmonitor.com/~r/feeds/science/~3/gWkiX1FlfBw/Spacewalkers-hunt-for-leak-on-International-Space-Station

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