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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.'"
What's weird about jumper cables in space? A set of heavy gauge wires that can take lots of current, with universal connectors on either end? Sounds incredibly versatile. I'd never leave Earth with out them, packed right next to my towel.
You much be one of those people who take your car to the dealer to get an oil change.
The problem is that the ISS ultimately rejects heat by radiating it away through radiators mounted on the solar array wings - and water would freeze and plug up the radiators.
So instead, they use a water loop to cool the atmosphere and equipment, and then transfer that heat to the ammonia system which then circulates through the radiators. (It's pretty easy to design the system such that there is minimal ammonia piping (and thus a minimal chance of an accident) inside the manned spaces.) Since ammonia freezes at a much colder temperature than water, this means it's much easier to keep the coolant moving at a rate where it radiates enough heat to be useful but still stays warm enough to not freeze.
It's going to be a complex trade off to choose a coolant, and few people seem to realize that NASA does take into consideration cost and availability when making their choices. They aren't so good at controlling costs as they might be, which is understandable since overall they're working at the bleeding edge of engineering, but that doesn't mean they don't try.
And really, there's isn't much of a difference between ammonia or anything more exotic because even something 'safe' (like nitrogen for example) is still going to rapidly displace the oxygen from the air (that is, reduce the effective partial pressure) if there's a leak because of the small volume of the breathable atmosphere.