Mark Tabone, via Facebook asked:
Long time listener, first time questioner. Given the temperature extremes on the surface of Mars, what design features are used to keep the rover components from freezing? Regards from Sunny Queensland.
David - Very good question. First of all, the nuclear power source on the back of the rover produces a bit over 100 watts of electrical energy, but it also produces 900 watts of thermal energy. And they actually have a fluid loop that takes the heat from the radioactive and runs it across what they call ‘rover avionics mounting platform’ where all the instruments are connected. And so, that keeps us inside the rover in kind of a shirtsleeves environment. Now, the instruments outside the rover do have to contend with this very bitter cold temperatures during the nights.
Chris - John, what about your experience on Titan that’s minus 180 whatever it is, degrees C?
John - Yes. I mean, you think Mars is tough but Titan is a lot colder, I think. Thermal design for spacecraft is very often one of the most challenging parts of the whole business. In the case of the Huygens probe, as I guess is true with Curiosity, you’ve got two extremes. You’ve got the extreme heat generated by the high speed entry into a planetary atmosphere and then once you’ve landed on the surface, you’ve got extreme cold. So it’s really all about, I would say, good design, good thermal design and generally conserving the little heat that you generate within the probe. You have to go to what to me, as a scientist, seems like ridiculous lengths. You even worry about the tiny amount of heat that is conducted down a very, very thin electrical cable and you have to use special electrical cable which is a good electrical conductor but a poor thermal conductor so, attention to detail at the minutest level.