Snowflake-like crystals spurted from an ammonia hose as spacewalkers performed coolant system repairs outside the International Space Station this morning, but managers on the ground believe the leak poses no danager. More than four hours into a planned seven-hour spacewalk, NASA astronauts Doug Wheelock and Tracy Caldwell Dyson have removed one of four coolan lines from a failed ammonia pump module.
That's a first step toward restoring a coolant system that's been down since the pump module broke last Saturday.
The pump served the right half of the outpost's U.S. segment. Only the left half is currently functioning, leaving no backup.
If a serious enough ammonia leak contaminated their spacesuits, the spacewalkers might have had to stop working to begin a time-consuming procedure to "bake out" the ammonia in sunlight. Wheelock easily removed a first coolant line that didn't contain ammonia. The first ammonia-filled line is taking longer, after it spurted the crystals Wheelock described as "tiny snowflakes" and the quick disconnect valve appeared to get stuck.
"This thing is not budging," Wheelock radioed.
Mission controllers hope a pass through orbital night will cool the ammonia enough to relieve some pressure in the line, loosening the valve.
If all the lines are freed, Wheelock will continue to disconnect and the boxy, 780-pound pump module from a position at the end of a 58-foot robotic arm controlled by fellow Expedition 24 flight engineer Shannon Walker.
The failed pump module, which Wheelock said showed no obvious signs of damage, will be stowed temporarily on the station's football-field length central truss until a second spacewalk planned Wednesday.
The spacewalkers will retrieve one of four spare pump modules from a platform beneath the Quest airlock, called External Stowage Platform-2, or ESP-2.
They hope to bolt the spare to the Starboard 1 truss segment and hook up as many connecting cables as time allows, but the spacewalk is running behind schedule.
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