Emergency Spacewalk: Astronauts Hope New Pump Fixes Ammonia Coolant Leak

NASA astronauts Chris Cassidy (top) and Tom Marshburn work outside the International Space Station after replacing an ammonia coolant pump on May 11, 2013. CREDIT: NASA TV

Two spacewalking astronauts may have fixed an ammonia leak outside the International Space Station today (May 11), perhaps bringing the outpost's vital cooling system back up to full strength.

Clad in bulky spacesuits, NASA astronauts Chris Cassidy and Tom Marshburn replaced a pump control box thought to be responsible for the leak of ammonia, which cools down the orbiting lab's systems.

It looks like this fix did the trick, as no ammonia flakes were seen streaming into space when Mission Control turned on the newly installed gear.

Chris Cassidy

"We're not seeing anything," Cassidy said at around 12:35 p.m. EDT (1635 GMT), several minutes after the pump was turned on. "No snow."

NASA officials stopped short of declaring total victory, however, saying that time will tell if the fix holds.

"It will take some diagnostics, still, over the course of the next several days by the thermal systems specialists to fully determine that we have solved the problem of the ammonia leak," NASA spokesperson Rob Navias said during live mission commentary. "But so far, so good."



Cassidy and Marshburn floated outside the space station at 8:44 a.m. EDT (1244 GMT) today, beginning what officials described as a six-hour detective's investigation to find — and hopefully fix — the ammonia leak.

Cassidy, who led the spacewalk, reported seeing "no smoking gun" as he and Marshburn began their inspection of the old ammonia pump control box, one of several on the space station's far left segment, known as the Port 6 truss. It is part of the cooling system for the two wing-like solar arrays extending from the Port 6 segment.

Upon removing the box, the spacewalkers still saw no signs of ammonia flakes.

Tom Marshburn

"It looks really, really clean, surprisingly so," Cassidy said while peering deep inside the box using what looked like a dentist's mirror.

Still, he and Marshburn proceeded to swap out the box, fitting a spare in its place.

The ammonia leak was first spotted by space station astronauts on Thursday (May 9), when the crew reported seeing flakes of frozen coolant floating outside.

They recorded video of the ammonia leak and sent it down to Mission Control for analysis.

While the leak posed no danger to the space station's crew, it could have impacted the amount of power available for daily operations on the orbiting laboratory if left unchecked, NASA officials said.

So Cassidy and Marshburn were sent out on an emergency spacewalk to attempt a fix.