By Geoffrey Mohan
12:39 PM PDT, May 11, 2013
Astronauts replaced a leaking component on the International Space Station after a 5-hour, 30-minute spacewalk, NASA reported.
Engineers Chris Cassidy and Tom Marshburn completed their spacewalk at 11:14 a.m. PDT Saturday, after gingerly gliding out to one of the station's trusses, where ammonia coolant had been seen leaking since Thursday. The coolant is used to control the temperature of one of eight solar arrays that power the station.
The pair, who had worked in tandem during spacewalks twice before, removed the 260-pound pump controller box from the P6 truss and replaced it with a spare stowed nearby.
Controllers in Houston tested the new pump while the spacewalkers watched for any fresh signs of ammonia snowflakes. Although there were no visible signs of a leak, the coolant system will need to be monitored over the long term to check for any loss of ammonia, NASA said.
"No leaks!" Expedition 35 Commander Chris Hadfield tweeted shortly after the walk finished. "We're bringing Tom & Chris back inside. In two days Tom, Roman & I return to Earth in our Soyuz. This is an amazing place & time."
The spacewalk ended on an emotional note. As the astronauts prepared the reenter the station, Cassidy expressed his gratitude to Marq Gibbs, longtime lead diver at NASA's Sonny Carter Training Facility Neutral Buoyancy Laboratory (NBL), who died unexpectedly last week at age 43. Spacewalkers practice in the facility, assisted by the divers.
"Chris Cassidy, Navy SEAL and lead spacewalker today," Hadfield tweeted afterward. "The nicest iron man you'll ever meet." He included a portrait of Cassidy in his spacesuit.
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