NASA waits to see if space station coolant leak is fixed after spacewalk

Astronaut helmet camera captures video of NASA engineers Chris Cassidy and Tom Marshburn replacing a pump on International Space Station suspected of leaking ammonia.

By Tariq Malik, Space.com

Two spacewalking astronauts may have fixed an ammonia leak outside the International Space Station on Saturday, 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 theleak 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.

"We're not seeing anything," Cassidy said at around 12:35 p.m. ET, several minutes after the pump was turned on. "No snow." [Emergency Spacewalk to Fix Space Station Leak in Photos]

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 theammonia leak,"NASA spokesperson Rob Naviassaid during live mission commentary. "But so far, so good."

An emergency spacewalk Cassidy and Marshburn floated outside the space station at 8:44 a.m. ET Saturday, 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.

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NASA waits to see if space station coolant leak is fixed after spacewalk