Wednesday, March 02, 2011

Astronaut Tackles Especially Hazardous Duty

Discovery astronaut Alvin Drew just finished an especially hazardous spacewalking operation outside the International Space Station, venting toxic ammonia from a failed coolant pump.

Using a specially designed tool, Drew sprayed 10 pounds of residual ammonia into open space -- a job that took about two minutes to complete.

"Good job, Al," said Discovery mission specialist Nicole Stott, who is directing the spacewalking work from inside the station and the docked shuttle.

Drew took great care to spray the ammonia out and away from the station. Ammonia crystals can stick to a spacewalker's spacesuit and could contaminate the closed-loop atmosphere inside the joined shuttle-station complex. In that event crew members would be exposed to the highly toxic substance.

Spacewalk planners had Drew perform the ammonia venting early in the excursion. By doing so, any ammonia crystals that might contaminate his suit would have time to "bake" off -- to sublimate when exposed to sunlight.

There is no indication that any ammonia crystals stuck to Drew's suit. Flight controllers saw crystals float by Bowen and asked him to double check his suit. They also asked Drew to double check the nozzle of the tool he used to vent the toxic coolant.

The ammonia pump failed last summer. Spacewalker Stephen Bowen stowed it on an external stowage platform during a spacewalk on Monday.

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