The discussion centers on selecting the optimal material for a heat exchanger in a spacecraft, specifically under vacuum conditions. Initial considerations included ceramic blends capable of withstanding temperatures up to 2500°F. However, participants highlighted the need for materials like molybdenum (Mo) and tantalum (Ta) alloys, particularly ASTAR alloys (811C, 1211C, 1511C), which offer superior properties at high temperatures. The conversation also emphasized the importance of understanding temperature units and their implications on material performance.
PREREQUISITESEngineers, materials scientists, and aerospace professionals involved in spacecraft design and thermal management systems will benefit from this discussion.
Which kind of degree?Melbourne Guy said:
How so?Rive said:
°F, °R, °C or K? The radiator rejects heat to space, so that implies a heat source of a greater temperature. 2500°F would be manageable with a Mo alloy (mp 2883 K), while Nb (mp 2741 K) might be too soft. If 2500°C (Nb would liquid, Mo would be creeping or flowing), the one would have to use a Ta or W alloy (Ta, mp 3269 K; W, mp 3683 K). Ref: W. D. Klopp, "Technology Status of Molybdenum and Tungsten Alloys," Proceedings of the first symposium on Space Nuclear Power Systems, M.S. El-Genk and M. D. Hoover, Eds., Orbit Book Company, 1985. The symposium was held in Albuquerque, New Mexico.Melbourne Guy said:
I'm not aware of the 'R' units, @Astronuc, but thank you for the detailed suggestions, and note that the other side of the exchanger is even hotter. I'll take a look at the ASTAR alloys, I've not come across them beforeAstronuc said:
°R is the absolute scale, Rankine, related to °F, as K is related to °C. T(°R) = T(°F) + 459.67°, and 1 K = 1.8°R, or 1.8*T(K) = T(°R). °F, °R are in the English system (lbm, ft, s), while °C, K are used in SI or MKS system. The 2500 reminded me of 1371°C (2500°F) or about the melting point of many steels. Ni-alloys are melting by around 1430°C, so at 1371°C, they would have very little strength and would probably be 'flowing' under low to moderate stress.Melbourne Guy said:
They are somewhat esoteric as far as alloys go.Melbourne Guy said:
Esoteric is good, this is sci-fi, after allAstronuc said:
Then maybe it's better to leave it like that.Melbourne Guy said:
It's just absurdly high. Usually a (thermal) power plant has a 'hot leg' around a few hundred Celsius at most, and your spacecraft has its 'cold leg' higher without utilization?Melbourne Guy said:
It's dumping the heat of the bubble drive, which folds spacetime like an Alcubierre warp drive and that generates significant thermal load! Or at least, I've now decided it does, based on this threadRive said: