Can’t you heat exchange inside the satellite, and make one part of the satellite incredibly hot so that it radiates a lot and dissipates.

This is just a question. I have no expertise at all with this.

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pas 15 hours ago | parent | next [-]

Yes, but you need energy to pump heat, and that has an efficiency maximum (thx ~~Obama~~ Carnot), and radiative cooling scales with the ~4th power of the temperature, so it has to be really hot, and so it requires a lot of energy to "cool down" the already relatively cool side and use that "heat" to heat up the other side that's a thousand degree hotter.

All in all, the cooling system would likely consume more energy than the compute parts.

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parl_match 15 hours ago | parent | prev | next [-]

yes. it is how sats currently handle this. its actually exponentially effective too P = E S A T^4

requires a lot of weight (cooling fluid). requires a lot of materials science (dont want to burn out radiator). requires a lot of moving parts (sun shutters if your orbit ever faces the sun - radiator is going to be both ways).

so that sounds all well and good (wow! 4th power efficiency!) but it's still insanely expensive and if your radiator solution fucks up in any way (in famously easy to service environment space) then your entire investment is toast

now i havent run the math on cost or what elon thinks the cost is, but my extremely favorable back of hand math suggests he's full of it

	▲	godelski 14 hours ago \| parent \| next [-]
		Be careful with the math there. While a 4th power is awesome you got the Stefan-Boltzman constant to consider and that's on the order of 10^-8 Radiative power is really efficient for hot things but not so great when you're trying to keep things down to normal levels. Efficient for shedding heat from a sun but not so much for keeping a cpu from overheating...
	▲	FabHK 9 hours ago \| parent \| prev [-]
		Pet peeve: T^4 is not exponential in T, it’s polynomial. For exponential, T must be in the exponent, e.g. 2^T or so. Still, pretty effective. Having said that, agree that Elon is full of it.

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TrainedMonkey 15 hours ago | parent | prev | next [-]

Good intuition, that is generally how radiators work in space.

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rcruzeiro 15 hours ago | parent | prev | next [-]

You can. This is how it is currently done, but it is not easy. It needs to have a large enough surface area to radiate the heat, and also be protected from the sun (as to not collect extra heat). For a data centre, think of an at least 1000m2 heat exchange panel (likely more to train a frontier model).

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afiori 9 hours ago | parent | prev | next [-]

Sure but if it was a good idea we could do it on earth too and datacenters could stop gurgling a city worth of water

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thinkingkong 15 hours ago | parent | prev | next [-]

You definitely _can_ the question is, can you do it by enough for a reasonable amount of money. There are a few techniques to this but at the end of the day you need to radiate away, the heat otherwise it will just keep growing. You cannot keep pumping energy into the satellite without distributing the same amount back out again.

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kamaal 13 hours ago | parent | prev | next [-]

>>This is just a question. I have no expertise at all with this.

On the similar lines, why can't one run a refrigerator in space?

	▲	jdranczewski 6 hours ago \| parent [-]
		You can, but the heat needs to go somewhere, and now you're back to square one, with "how do I get rid of all this heat". Earth refrigerators have a large heat exchanger on the back for this purpose. In fact now you need to get rid of both of the heat your compute generates and the energy your refrigerator pump uses - an example people often give is that a fridge with an open door actually heats the room, as it spends energy on moving heat around pointlessly.

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prpl 15 hours ago | parent | prev [-]

yeah if you want a heat thruster