RTGs in a hot environment.

[Tw1]

As I'm failing to get to sleep, and my mind was buzzing with ideas, one thing that occurred to me, that RTGs need a hot area, and a cool area, but the temperature on Eve is very hot.

My recent probe measured about 150c, which is a fair bit. Less temperature differential between the nuclear material and the heat sinks means less power.

Should the RTGs run less effectively under this heat? Or shouldn't that be enough in this case? Not sure if insulation would have a positive or negative effect here.

(Hypothetically, they don't seem to be effected currently.)

Edited May 20, 2013 by Tw1

[satcharna]

It is possible to power an RTG from the emissions of light from the nuclear fuel as well, it's possible that this is what the kerbals are doing.

[TelluriumCrystal]

I've never thought of that before... I suppose efficiency would be reduced to an extent.

[astocky]

As I'm failing to get to sleep, and my mind was buzzing with ideas, one thing that occurred to me, that RTGs need a hot area, and a cool area, but the temperature on Eve is very hot.

My recent probe measured about 150c, which is a fair bit. Less temperature differential between the nuclear material and the heat sinks means less power.

Should the RTGs run less effectively under this heat? Or shouldn't that be enough in this case? Not sure if insulation would have a positive or negative effect here.

(Hypothetically, they don't seem to be effected currently.)

Correct they need a temperature differential. However once the entire RTG has reached the heat of Eve which will still happen - think heat soak. You still have the radioactive source on the inside heating it, therefore the inside is still hotter than the outside. The real question though, is how much hotter can the outside be before you have to melt the inside to make any useful power.

[HoY]

I don't know the math behind this, but also consider how much less efficient the heat sinks are in a vaccume compared to inside an atmosphere, regardless of the air temperature. They don't magically make heat go away, they dissipate the heat by providing a larger surface area for outside particles to come into contact with it and absorb some of its thermal energy. In a vaccume there's nearly nothing to help with that process. A dense atmosphere like eve would be ideal for heat sink technology!

Edit; think of it this way. Life survivability in 0C air vs 0C water. Except backwards

Edited May 20, 2013 by HoY

[DMagic]

Heat in a vacuum is dissipated by emission of IR radiation, called radiative cooling. It's not as effective as the convection cooling you get in the atmosphere. You can how big the radiators have to be in pictures of the ISS, they are the big flat protrusion coming out from many different sides of the station, the ones that aren't solar panels.

A dense atmosphere would be great, but only if the actual temperature was low. If the atmospheric temperature on the surface was very high then I would think an RTG would be less effective.

As was mentioned above, the core of the RTG would still be hotter than the surrounding atmosphere, but the relative difference in temperature seems like it would be less. Instead of, say, a 500K core and 275K heatsink, you might have a 700K core and a 475K heatsink. The difference is the same, but the relative increase of the core over the heatsink is less (an 82% increase vs. a 47% increase).

Does anyone know if this is right? or if it makes sense? And would that difference in relative temperature differential affect the efficiency of the generator?

Now I've got myself confused...

Edited May 20, 2013 by DMagic

[Qumefox]

astocky is correct. The radioactive heat source would still maintain a temperature differential, thus an RTG would continue to function regardless of external temperatures. However, as he also said, the maximum limit will be the point where the components of the RTG start melting.

And HoY. Heatsinks dissipate heat in two ways. Through convection to an outside medium(air/water etc) and radiantly. There are trade offs to both methods but I believe in space, heatsinks work better than you'd think since there is nothing to insulate the IR output. Also in space, if that IR radiation isn't uniform, it will actually cause a slight propulsion to the craft.. This was finally figured out to be the cause of the anomalous slight acceleration forces that showed up in the voyager probes over time.

[HoY]

I realized I forgot to mention the IR aspect but didn't bother adding that with another edit, Ty

Edit, also tho it has no effect on gameplay there is sure to be air currents on eve, and wind chill factor should be counted too

Edited May 20, 2013 by HoY