Cooling Pump Malfunction On ISS

eldavojohn writes "On Saturday at 8pm GMT, the crew of the International Space Station awoke to alarm bells as one of two ammonia pumps shut down due to a spike in power. Their backup cooling (Loop B) is functioning as designed and NASA released an official statement: 'The crew is in no danger, but will need to work additional troubleshooting on Sunday to keep the station in a stable configuration, including the installation of a jumper cable to maintain proper cooling to the Zarya module in the Russian segment.'"

Comments

Hmm...

[fuzzyfuzzyfungus]

I'm surprised that they would be using ammonia coolants, rather than something more exotic and less toxic.

Ammonia makes perfect sense in industrial ice plants and rink chillers and stuff, being dirt cheap, and not especially dangerous when you have an entire planet's atmosphere to dilute the leaks. Plus, it doesn't have the Ozone-eating properties of the CFCs.

In space, though, everything is expensive by default, having been carried into earth orbit, there isn't much of an ozone layer to worry about, and you really don't have enough breathable atmosphere available to risk contaminating it with anything unpleasant. Ammonia seems like a curious choice.

Anybody know why they would have gone with that?

Re:Hmm...

[vlm]

I'm surprised that they would be using ammonia coolants, rather than something more exotic and less toxic ... Anybody know why they would have gone with that?

IF its an absorption cycle system, you just can't do better than ammonia. Its hard to find any refrigerant gas that dissolves better in water... absorption cycle is nice on planet earth, no moving parts, no lubricant compatibility issues. In space you need pumps, however.

On the other hand, if its a vapor-compression system like your fridge at home, yes it is in fact a pretty cruddy choice and any of the freon series would kick its butt (as a refrigerant, anyway)

On earth you can play games with gravity to prevent/reduce slugging the compressor in a vapor-compression system. Not sure how you do that in space. Slugging a compressor is when load/airflow is low and you feed a gulp of liquid into the intake instead of moderately hot gas. Its kind of a shock to the innards, its the pump equivalent of eating at Taco Bell...

http://en.wikipedia.org/wiki/Refrigeration#Cyclic_refrigeration