Tuesday, April 13, 2010

Stuck valve could pose problem for station

Discovery astronauts successfully installed a new coolant tank outside the International Space Station over the course of three spacewalks, but a stuck valve on a related piece of equipment could pose a problem for ongoing station operations.

Ground controllers have not been able to activate the newly installed ammonia tank because a valve is stuck closed in a nitrogen tank used to pressurize the coolant lines.

In a matter of days, the station will enter a roughly two-week period in which the sun's angle keeps one side of the outpost hot and the other side cold.

Temperature swings cause the station's ammonia coolant to expand and contract, a process managed by a bellows within the ammonia tank hardware that is fed by nitrogen. The bellows wouldn't work without normal nitrogen flow.

If the valve remains shut, the ammonia loop serving the starboard side of the station might need to be shut down, which could have implications for the outpost's ability to maintain a full crew of six.

Ron Spencer, the lead space station flight director during Discovery's mission, said today that ground controllers have a variety of troubleshooting procedures to try to open the valve. He said a last resort would be to swap out nitrogen tanks on a spacewalk.

It was not clear how soon such a swap would need to occur, or whether it would be handled by a shuttle or station crew. All those options are being studied, he said.


Anonymous said...

Why not send out an astronaut to just fix the valve?

Rick Steele
Sarasota, Florida

James Dean said...

Rick -- station managers said the only spacewalking fix would be to fully swap out the nitrogen tank, so apparently the spacewalkers wouldn't be able to access and work on the valve in question in space. Hopefully troubleshooting procedures directed from the ground will get the job done before it gets to that point.