3 ms·

Yeah, the materials issues dominate design basics. They've looked at HfC and HfCN as nuclear engine materials (m.p. ~3950°C), pretty exotic. I feel like if des

Yeah, the materials issues dominate design basics. They've looked at HfC and HfCN as nuclear engine materials (m.p. ~3950°C), pretty exotic. I feel like if designers would drop their effort to wring out the last increment of Isp from nuke engines and reduce temperatures to ~2000°C, it would give faster development. There are many materials that can live in 2000° hydrogen for >100K hours. There's an old Rand study that showed H2 would give an Isp >1100 at 1 atm chamber pressure (!), temp ~2000°C, exhaust pressure 10e-4 atm. Seems worth exploring.

lazide 3y ago
That does sound more reasonable! Part of the issue I suspect why reasonable isn’t being considered is that I don’t expect anyone to have a reason to really use them right now regardless - all the nuclear propulsion designs have a high ‘fixed’ weight cost in the reactor, so would only make sense overall in a ‘hundreds of tons to Uranus ASAP’ type situation, where the overall weight for thrust can be lower due to the better fuel efficiency. So far we thankfully haven’t had a reason to really need to do that right now. And if we’re doing theoretical designs, why not make it ‘interesting’? On a side note, if we’re considering crazy ideas - my favorite is the one that makes Project Orion seem clean! https://en.m.wikipedia.org/wiki/Nuclear_salt-water_rocket https://en.m.wikipedia.org/wiki/Nuclear_salt-water_rocket Any rocket which calls for ‘salts of plutonium’ as fuel has to be cool.