[kijin]

I'm curious about the foam, too. Normally, foam contains a lot of air. But that kind of foam will blow itself apart in a vacuum. How do they make foam where all the air pockets are replaced with vacuum? Is vacuum-filled foam a better or worse insulator than air-filled foam?

[jstanley]

It could be open-cell foam instead of closed-cell foam. In earth atmosphere the cells would still be filled with air, but the air would be able to leave without blowing the foam apart.

[rubatuga]

Foam can be made and slowly evacuated. Vacuum filled foam is a better insulator

[noir_lord]

I think it would be better if it was vacumn voids rather than air filled since air will conduct heat via conduction.

[reaperducer]

Normally, foam contains a lot of air. But that kind of foam will blow itself apart in a vacuum.

In the video, Thermal Protection System Engineer Betsy Congdon says it's 97% "air."

I can't say whether it's actually air, or she's simplifying things for the general public or not.

She also says twice that "water" is used in the radiators. But I'd have to believe that NASA's using something that absorbs/dissipates heat a little more efficiently. Perhaps whatever it is will end up in desktop gaming rig cooling systems eventually.

[zaarn]

They used deionized water, not unusual for gaming rigs either.

The temperature range is about 15C to 125C, at high pressure this is most ideal for use with water and water itself is a rather good coolant.

[petre]

The only substance that can transport more energy than water that I know of is ammonia. But it's quite corrosive and it has to be pressurized at 50-100 bar to make a difference.

[dghughes]

And if the foam cells have a vacuum in them (in? lack of?) how does it not implode when on earth.

[noir_lord]

The difference between Vacumn and 1atm is 14psi, bike tires pumped to between 50-120psi (on my road bike for example), 14 psi isn't that large a pressure for a reasonably strong/stiff material.

[dghughes]

I know what you mean but in a way I think there is a difference since the material has to withstand inward pressure; compressive forces.

A tire/tyre rubber has tensile strength, most (all?) pressure vessels on earth are tensile. It seems odd the difference between compression and tension when it comes to certain forces.

Anyway, I just though it would matter.