cpus in space

[oldman420]

in the absense of an atmosphere how would you best cool a chip? does an object radiate heat in space? how do you get rid of the heat generated in no atmosphere?

 

[asm0deus]

space is cold so maybe you could get away without having to use a hsf

 

[DrPizza]

space is cold, but space isn't very dense. There are three ways to transfer thermal energy: convection, conduction, and radiation. Here's a site to learn more about these:

Including equations

As far as space being cold being sufficient to cool something, think about it this way. How could I cool a molten hunk of lead quickest? Putting it in a refrigerator at 40 degrees? (air cooling) or putting it in a bath of water at 40 degrees? Water would cool it the best. Now, remove the air from the fridge, and it's going to cool a lot more slowly, because it won't be in contact with air. It will still radiate the excess heat away though.

 

[DrPizza]

Originally posted by: oldman420
in the absense of an atmosphere how would you best cool a chip? does an object radiate heat in space? how do you get rid of the heat generated in no atmosphere?

Does an object radiate heat in space? Fortunately, YES! The sun is an example.

 

[jagec]

It would have to be strictly radiative cooling, which means HUGE heatsinks.

 

[Armitage]

Yep ... cooling is one of the big issues for spacecraft.
Another big issue is radiation hardening. As feature size on chips gets smaller it gets more susceptible to radiation induced upsets. Which is why you need very expensive rad-hardened hardware. Which, as of a few years ago when I followed this stuff, had the power of about a 486 for general purpose processors.

 

[uart]

Radiation power increases with the fourth power of temperature, so it might be worthwhile to use a heat exchanger (active cooling) between the cpu and the radiator (sink) so that you can operate with a HS temperature somewhat greater than the CPU temperature.

 

[jagec]

Originally posted by: uart
Radiation power increases with the fourth power of temperature, so it might be worthwhile to use a heat exchanger (active cooling) between the cpu and the radiator (sink) so that you can operate with a HS temperature somewhat greater than the CPU temperature.

You must mean heat pump?

 

[oldman420]

you would need some sort of resavoir for the heat to acumulate into its got to go somewhere also any mechanicle contraption is going to create more heat yet. a peltier with some massive heat absorber on it that will radiate enough into space to keeps things cool. maybe it has to do with surface area. ie a thin sheet of material with a large surface area?

 

[DrPizza]

Yes, the surface area does matter. Take a look at the Stefan-Boltzmann Law of Radiation in the link I provided above.

Energy radiated per second - emissivity*Stefan-Boltzmann constant *surface area*Kelvin temperature^4

S-B constant = 5.67*10^-8 J/(s m^2 K^4)

So, double the surface area and you double the rate at which energy is radiated.

 

[Cogman]

Cooling would definitly be a big problem. After all even in near absolute zero conditions, those in space are more likely to fry from radation then freaze to death. (red planet, or whatever that movie was, was completly off. That guy would not have frozen like that. More likely nitrogen bubbles would have formed and killed him, boiling blood....

 

[Peter]

Heat budget is one of the major constrictions in orbital vehicals. Computer boards used therein must be cooled conductively, transferring their entire heat into the rack they're in. From there, the heat is essentially brought out onto the outer surface of the vehicle, to be radiated out into space. Peltiers are silly because in the overall equation, they just generate even more heat.

For this and power limitations, the stuff up there is all surprisingly weak in computational power.

 

[oldman420]

if you had a large surfac area and part of it was in the sun could that actualy create more heat

 

[Armitage]

Originally posted by: oldman420
if you had a large surfac area and part of it was in the sun could that actualy create more heat

Yep, that's another important bit. Keep the solar panels pointed at the sun, and the radiators toward deep space.