ISS Coolant Pump Restarted After Successful Spacewalks

Yesterday, two astronauts completed a seven hour spacewalk to finish installation of a spare coolant pump after a failed coolant pump forced a partial shut down of the ISS. As of late yesterday afternoon, that pump is online and operating normally: "The new pump now is considered fully functional, but it will take some time to fully reintegrate the pump and Loop A of the two-loop external cooling system. Teams at mission control are following a schedule that should allow the restored cooling loop to be fully activated and integrated into the station’s cooling system on Christmas Day, Dec. 25. ... Electrical systems that depend on cooling from Loop A will be repowered or moved back from temporary support on Loop B gradually on Thursday, Friday, and throughout the weekend."

Comments

Not so hot any more

[Anonymous Coward]

That's cool.

Re:Not so hot any more

[SJHillman]

It's just to keep the astronauts cool in case they ever have to land the ISS on the sun and can't wait for night time. Duh.

Re:Not so hot any more

[SpaceCracker]

I'm not so sure about that. I thought that the close-to-vacuum of space does not conduct heat that well. The "low" temperature of space just means whatever particles happen to be there on average don't move all that fast. Without a cooling system, the only way for the electronics to lose excess heat is by black-body radiation, which is totally insufficient relative to the rate at which heat is generated (think of your mobile phone, PC, laptop or TV and how hot they get).

Re:Not so hot any more

[fisted]

You probably missed the

Yours,
Armchair engineer

part

Re:Not so hot any more

[SpaceCracker]

I sit-in-the-armchair corrected.
Happy Holidays.

Re:Not so hot any more

[Anonymous Coward]

it would take a long time to even cool down to the surrounding temperature in outer space, such a long time that the heat generated from within space station effectively negates the passive cooling

Re:Not so hot any more

[JustOK]

Space is cool again? That's cool.

Re:Not so hot any more

[Deadstick]

As fisted said, you apparently fell for a gag, but no biggie. Since you're interested in the subject, here are a few additional details.

Vacuum itself has no temperature, because temperature is a measure of the motion of particles, and there are none. Space is not a perfect vacuum, having very roughly one particle of one sort or another per cubic meter, and in principle you could calculate a temperature based on their motion, but it would never exchange any meaningful amount of heat with an object.

Vacuum will not conduct heat either, and without conduction there is also no convection, so the only means of heat exchange left is radiation. Any two bodies separated by vacuum will exchange heat in proportion to the difference between the fourth powers of their respective temperatures -- and this is where a very big variable comes into play.

Excluding the Sun and Earth, the rest of the universe acts approximately as if you were surrounded by a black surface at a temperature of only 3 kelvins -- almost absolute zero. That means you will lose heat very fast.

OTOH, the Sun approximates a blackbody at nearly 6000 kelvins. That means if you're exposed to it, you'll absorb heat REALLY fast.

So whether you're in sunlight or in the shade makes a huge difference. If a satellite receives more heat than it radiates away, its temperature will keep going up, and vice versa. The designer has to do a lot of tricks to keep the temperature under control. You can get rid of excess heat with radiators that expel heat into cold space on one side, and have a shiny surface on the other side to reflect away what arrives from the Sun. (car analogy)The coolant pumps on the ISS do the same thing the water pump in a car does: transferring heat from the interior to the radiators (/car analogy).

Re:Not so hot any more

[fatphil]

Sure, space is always cool, but in these liberated modern times we can twist it into a story about blokes who are living together in space.

I shouldn't mention that, lest the ultra-conservatives conclude this is perverting the wide-eyed youth and decide the to slash the NASA budget.

Re:Not so hot any more

[Alwin Henseler]

Without a cooling system, the only way for the electronics to lose excess heat is by black-body radiation, which is totally insufficient relative to the rate at which heat is generated (think of your mobile phone, PC, laptop or TV and how hot they get).

Electronics exposed to the vacuum of space, will still be bolted to the ISS somehow, so can use the structure as heatsink. Electronics inside the ISS can use air cooling in addition to that.

For the structure as a whole, black body radiation will be the only way to get rid of excess heat (unless they'd pump excess heat into something, and toss that out. Which seems impractical to say the least :-).

But there can be big temperature differences depending on what's white/reflective or dark, and what's facing the sun or the cool dark of space. I suppose a cooling system would serve to distribute (pump) heat between where it's in excess, and where it can be dumped (radiator).

Re:Not so hot any more

[Geoffrey.landis]

Electronics exposed to the vacuum of space, will still be bolted to the ISS somehow, so can use the structure as heatsink.

Well, sort of. Electronics bolted to the ISS can conduct waste heat to the structure, but the heat still needs somewhere to go-- what you're just saying is that it can use the thermal conductivity of the ISS structure as a heat pipe, and the structure of the ISS as a radiator. Which is theoretically true, but there's only a limited amount of heat you can get rid of that way.

Electronics inside the ISS can use air cooling in addition to that.

Again, air "cooling" can move heat around, but it still has to go somewhere, which ultimately means it needs to be radiated to space.

Plans for a replacement?

[Anonymous Coward]

It is outstanding that they had the foresight to stock a replacement for what is apparently a very large, but crucial, component. I'm curious if anyone has heard whether there are plans to send them a new spare, just in case they go through this again? Was the original spare brought up via the shuttle and can a new one be brought up without the shuttle?

Re:Plans for a replacement?

[Anonymous Coward]

An article in CSM noted that it weighs 780 pounds and is about the size of a refrigerator
The first Space-x resupply mission carried nearly 2000 pounds... so weight is not an issue with putting another backup in place, not certain about dimensions
The cooling pumps are part of the 'big 12' systems that must be running for the ISS to function. I would imagine that the backup plans have backup plans which have their own backup plans

Too much egg nog last night.

[Anonymous Coward]

I read the headline as "ISS Coolant pump Retarded" - blury vision and whatnot.

I don't understand.

[Anonymous Coward]

If it was getting stuffy in there, couldn't they just open a window or something?

Re:I don't understand.

[fatphil]

"Hi! I'm the plumber who's going to fix the coolant pump"
<cue: cheey 70s synth music>

What about the spacesuit?

[TubeSteak]

They kept having problems with it and I'm much more interested in how they plan to resolve that set of issues.