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Post by kjakker on Apr 18, 2021 21:22:23 GMT
I just watched this video talking about nuclear thermal propulsion. Did the producer of the video make a mistake with regard to type of reaction mass? I am used to using methane for that in COADE yet he is saying that you would need to use hydrogen in a nuclear thermal rocket.
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Post by AtomHeartDragon on Apr 19, 2021 17:09:36 GMT
I just watched this video talking about nuclear thermal propulsion. Did the producer of the video make a mistake with regard to type of reaction mass? I am used to using methane for that in COADE yet he is saying that you would need to use hydrogen in a nuclear thermal rocket. Armour is the thing that makes the difference. Liquid hydrogen has piss poor density - if you want to not only store it but also put some armor around it you run into issues. OTOH methane performs much worse, but is also much denser so it takes much smaller volume and exposes much lower surface area that needs to be armored (mind you, hydrocarbons like methane might have some non-trivial engineering issues attached, namely solid carbon buildup). In general, the heavier your armor, the denser propellant you need. Another issue is that chemical engines perform less than optimally in COADE due to it not modelling non-stoichiometric combustion properly. IRL you'd burn, for example hydrolox, fuel rich, not only saving engine components from oxidation, but also increasing Isp while driving temperature down by having a lot of uncombusted hydrogen in the exhaust. In COADE, as far as I can tell, all the uncombusted mass disappears down a black hole. Combine it with somewhat optimistic solid core NTR performance and it really makes nuclear propulsion using variety of propellants come up on top. |
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