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Astronauts run into problems with second umbilical
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: August 7, 2010


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Four hours into today's spacewalk, astronaut Douglas Wheelock, after venting nitrogen used to pressurize coolant lines leading to a faulty pump module, has started demating ammonia line quick-disconnect fittings. The first quick-disconnect fitting, known as M4, closed easily and no ammonia leakage was observed. But he ran into problems with the second line, M3, which required more force to open. Using a lever tool, however, Wheelock got the second line unlatched, but a small amount of ammonia could be seen escaping.

"I see little sparklets of ammonia coming from the line," Wheelock reported.

"I copy. Are they continuous, or did you just see a few at first?" asked Oscar Koehler in mission control at the Johnson Space Center in Houston.

"It's just sort of random, like little tiny snowflakes," Wheelock said.

He was then asked to cycle the quick-disconnect latch, fully re-mating the connector with its internal valve open. More ammonia escaped as he moved the latch. He then ran into more problems trying to open the latch back up, presumably because of internal pressure.

After multiple attempts with the lever tool, he muttered "wow, that thing is not budging, Oscar." Astronaut Shannon Walker, operating the station's robot arm, moved Wheelock into a more favorable position and he tried again. But again, he was unable to re-open the latch. Koehler told him to take a break at that point and to wait for orbital darkness in hopes that the temperature change would reduce the internal pressure and make the latch easier to throw.

The M3 and M4 lines must be connected to a jumper box that will allow ammonia in the loop A coolant system lines to expand and contract as needed while the pump is replaced.

After demating all four ammonia line quick-disconnect fittings, the astronauts will disconnect five electrical cables. At that point, the spacewalkers will begin unbolting the pump module from the S1 truss so it can be removed. But first, the astronauts must resolve the problem with the M3 quick-disconnect fitting.

Wheelock and Caldwell Dyson are running well behind schedule at this point. Because of the observed ammonia, both spacewalkers will have to undergo a spacesuit decontamination "bake out" procedure at the end of the spacewalk. It is not yet clear if they will have time to install the new pump during today's spacewalk even if the old pump can be disconnected and moved out of the way.