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Comment by thrtythreeforty | Hacker News Reader

You could not. There would be no place to get rid of the waste heat.

You can radiate it away, but it would be really hard compared to just dumping it to atmosphere / water bodies. Especially as computers need quite low temperatures.

Here is some more analysis on the problem of radiating heat away in space: https://toughsf.blogspot.com/2017/07/all-radiators.html

Elton John told me that space is cold as hell. Presumably the ISS is putting its waste heat somewhere, but I don't really know the limitations of radiators in space.

- "Presumably the ISS is putting its waste heat somewhere"

Giant radiators:

http://claudelafleur.qc.ca/images/iss028e005676.jpg

https://en.wikipedia.org/wiki/External_Active_Thermal_Contro...

Fluid pipes are threaded through them for transferring heat. These contain mixed-phase ammonia: I believe it should condense from vapor to liquid under the radiators, the coldest point. That phase change adds a huge boost to their heat-carrying capacity.

A cubic meter of space has very little heat energy, that's true, but it's more about having only a few molecules here and there in any cubic meter of space. That leads directly to the problem though, that if there are no molecule to contact you and steal some kinetic energy and then leave, reducing your heat, the only option is to radiate it away. Radiating heat is exceptionally inefficient at rejecting heat from an object than using a material of some sort to sap away that heat with physical contact.

Space is around -270°C cold. The heat would dissipate so quickly, much better than even liquid nitrogen cooling.

Without convection or conduction?

ok to correct myself. Due to lack of much air, heat would only dissipate by Black body radiation. One would need to calculate if that could cool down the chips efficiently.

It won't. There is reason why we use fans. There is two ways to handle high heat loads, convection or evaporation. And you would run out of evaporative material in space pretty quickly.

I think this is a very popular mistake to make. It is sort of a well known bit of trivia, but only because everybody has to correct themselves on it at least once, haha.

If it's dissapating through black body radiation the temperature of space isn't really that relevant to cooling.

You can radiate heat from the surface of the earth into space via the sky, but you don't lose much energy that way.

> You can radiate heat from the surface of the earth into space via the sky, but you don't lose much energy that way.

That's not quite true. Black body radiation is the only reason why earth does not heat up much more. It's the only factor with a negative radiative forcing.

Solar radiation is the only main incoming source of energy, and black body radiation the only outcome with almost the same magnitude (which is huuuuge btw)

What I mean that building a system to radiate radiate energy into space from the surface of the earth isn't very cost effective, and it's undoubtedly far less expensive than building a system you would launch into space.

The actual surface of the earth has the advantage of being able to use the whole surface of the earth.

On earth you can use things like fans and evaporative cooling. It's far superior to making huge space radiators, but nothing is free.

You would think so, but that's not as simple as you would think. On Earth that cooling generally happens by conduction and convection to the air.

In space there is mostly no atmosphere, you have to radiate that heat which isn't quite as easy as it sounds: https://www.space.com/21059-space-station-cooling-system-exp...

If you think about why a vacuum flask or thermos is used to keep drinks hot (or cold) for an amount of time you'll realise that space / a vacuum is a very good insulator.

An object in space loses heat according to the Stefan-Boltzmann law of radiation. That use the fourth power of the temperature differential so you get boost from the background of space being -270C. BUT the Stefan-Boltzmann constant is 5.67 × 10−8 J/s · m2 · K4 and that is the problem.

You can do the numbers yourself but various internet sources suggest that spacecraft radiators can only cool between 100 and 350 W of internally generated heat per square meter. That is a big radiator for not much cooling.

Air cooling occurs by convection which is completely absent in space. Similarly, advection and convection seem unlikely to contribute much. That leaves mainly radiation which is a lot slower: https://en.wikipedia.org/wiki/Heat_transfer#Heat

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