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

HOWTO: Fixing stuff in space

[tomhudson]

1) Where's the Duct Tape?

2) Duct tape something ("including the installation of a jumper cable to maintain proper cooling to the Zarya module in the Russian segment");

3) Problem solved!

Is Feature!

[DWMorse]

Our cooling pump is now, for your convenience, a heating pump. For survival in the cold of space.

Ditch the pump...

[human-cyborg]

They should develop artificial gravity. That way their absorption chillers won't need pumps.

Much simpler.

Why human presence still matters

[mangu]

This is why it's still important to have humans in the loop.

We will most likely have human-equivalent machine intelligence in a few decades, but at this moment a piece of duct tape in human hands can do miracles that no amount of planning, programming, and design could allow a machine to perform.

Re:Why human presence still matters

[yodleboy]

wait a sec, if there were no humans on the ISS, much of its complexity would be unnecessary, eliminating the need to have humans in the loop. Specifically, i'm thinking of all the components that make it able to support human life, which seem to have a higher incidence of failure/issue. It's always a toilet or a/c unit freaking out up there.

Re:Why human presence still matters

[Jeremi]

Sounds like the right mentality to go to Mars/ Asteroids/ or anywhere else off this planet.

If you want a preview of what living off planet would be like, build yourself a water-tight metal cocoon, lock yourself inside, have it dropped to the bottom of the ocoean, and live inside it for the rest of your life -- no, you can't ever come back. Oh yeah, and for complete realism, you're not allowed to examine any fish or other lifeforms or collect any to eat, because off-planet, there won't be any.

Sorry to be a luddite flat-lander, and a bubble-burster on top of that, but after the first few weeks/months, living off-planet would be a hellish claustrophobic monotony punctuated only by the occasional crisis. By the time the first critical life-support system gave out and killed everyone, it's likely that most of the population wouldn't mind dying.

Perhaps someday terraforming or (less likely) discovery of human-friendly habitats will change that, but for now just there's no "there" there, and the costs for keeping humans alive indefinitely outside of Earth are incredibly high. We'd be much better off sending robots to explore until we develop the heavy-lift systems and/or automated-manufacturing technology to properly support an off-world colony.

Re:Why human presence still matters

[vlm]

after the first few weeks/months, living off-planet would be a hellish claustrophobic monotony punctuated only by the occasional crisis. By the time the first critical life-support system gave out and killed everyone, it's likely that most of the population wouldn't mind dying.

You make it sound like living in New York. I don't think it'll be that bad.

Re:Why human presence still matters

[Rich0]

Also its far cheaper to maintain a scope that is extremely nearby the space station, than it is to maintain with robots or shuttles.

Sure, if you don't account for the cost of the space station in the first place.

Why you'd spend hundreds of billions of dollars on a space station to save a few tens of millions of dollars on telescope repairs is beyond me...

Re:Sounds like Russian thing: JUMPER CABLES IN SPA

[human-cyborg]

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.

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...

[bloobloo]

Molecular weight of ammonia = 17
Molecular weight of R12 = 121

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

Re:Hmm...

[DerekLyons]

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.

Re:Hmm...

[vlm]

Reason 3 which I forgot to include, is radiation turns ammonia into harmless H2 and N2. Little to no effect on the equipment or thermodynamic properties at any reasonable concentration. If you catch enough gammas to break down 50% of the refrigerant, roughly 50% of the crew mass would have been broken down, indicating bigger problems.

Radiation turns fluorocarbons into fluorine and assorted debris. fluorine, at any concentration, is not good in anything except fluorine tanks. Anthropomorphizing it a bit, F likes to halogenate hydrocarbons like pump oil or plain ole oily contaminants leading to all kinds of entertainment. Its just nasty stuff even at the lowest concentrations. I suppose you could design and install a nice heavy halogen trap, but you'd never Really Know about the internal corrosion levels of the pumps and pipes without very expensive continuous maintenance. The entire refrigeration system would need to be halogen compatible. On earth its not an issue due to low radiation levels and frankly if my A/C pipes corrode out its not life threatening anyway. But not so good of an idea in space.

Finally ammonia is high temperature stable and if you somehow manage to dissociate it anyway, the N2 and H2 are mostly harmless and can be flushed out. On the other hand, SOME of the fluorocarbons have pretty nasty icky byproducts if you overheat them, by, say, the pump shutting down in full sunlight for a long time.

Re:Hmm...

[mmontour]

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)

In terms of performance, ammonia is one of the best refrigerants in vapor-compression systems. Freon is easier and safer for small systems but ammonia is preferred for large industrial applications.

Re:Sounds like Russian thing: JUMPER CABLES IN SPA

[slick7]

Well of course you wouldn't leave without them, Mr. Human-Cyborg.

That said, I agree fully. There are certain people in this world who, given a problem and some small versatile components, can fashion a solution. I don't mean simply the ones titled "engineer"; it's more of a personality trait. Duct tape, jumper cables, a good pocketknife, plastic sheeting, and a skein of rope can solve most everyday problems, and many that aren't so everyday.

For a while, I carried a small coil of Romex 3-conductor wire in my trunk. I don't know how it got there, but when a screw fell out of my car door's latch 150 miles from home, it was nice to have materials to make a makeshift replacement. Just 2 inches of one of the conductor, folded in half, and threaded into the hole. The plastic insulation held as threads, and I had a working screw.

...or better yet, carry AAA Plus, it's only $97 per year. For the ISS, I would go with SSS (Space Station Society) Plus because you get 4 free tows to a higher orbit each year.