are there any fissionable materials that can be refined on the moon?
The weight of the fuel is the least of the concerns with this scheme.
but getting into an accident and spraying it all over during liftoff is something of a concern
UK backs Rolls-Royce project to build a nuclear reactor on the moon
131–140 of 185 posts
Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#132Earlier quoted context omitted.
The same plan as for all the countless cases when they sent radioisotopes in space. Perseverance and Curiosity each have 4.5 kg of Plutonium-238 on board. Did that worry you?
Yes. And the lunar reactor will require more power and thus more fuel.
The plutonium 238 fuel in RTGs has a half life of 87.7 years:
https://en.wikipedia.org/wiki/Plutonium-238
Uranium 235, the fuel used in reactors, has a half life of 703.8 million years:
https://en.wikipedia.org/wiki/Uranium-235
This means that plutonium 238 is roughly 8 million times as radiotoxic as uranium 235, gram for gram. If this mini-reactor carries 4.5 tonnes of fuel it will be 0.012% as dangerous at launch as the power source for the Curiosity rover.
Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#133Can we build them for earth too? We need to quit oil yesterday.
The largest terrestrial consumer of oil is road transport (cars and trucks).
https://www.statista.com/statistics/307194/top-oil-consuming...
You can't put a nuclear reactor in a car. You can charge an electric car's battery using nuclear electricity, of course. But if you're just charging a terrestrial battery then nuclear power's attractive attributes for the Moon (like continuing to produce during a 14 day period of darkness) are less salient. Electricity sources like wind and solar power are likely to charge up the car's battery at lower cost.
Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#134… but why Rolls Royce? Also interesting that they didn’t pick a US nuclear company. This is obviously a boon to the contract winner. These decisions always have a political aspect to it. What does this signal? Edit: wow, massive oversight. I thought this was NASA. Nevermind! Still, the Rolls Royce choice isn’t obvious to me.
Rolls Royce already makes the nuclear reactors for the UK's current fleet of nuclear submarine, and is developing the reactor for the new SSN-AUKUS subs that are currently in the design phase. They also market a modular reactor for civilian applications. Presumably these are all based on a common core design and the research grant is to adapt it for space applications.
https://www.rolls-royce.com/innovation/small-modular-reactor...
Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#135Can we build them for earth too? We need to quit oil yesterday.
They already do:
https://www.rolls-royce.com/innovation/small-modular-reactor...
Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#136It will be interesting to see a modern design, rather that the something based on 1930s physics, 1940s construction methods, built in the 1950s and put into use in the 1960s like some of these military reactors they used for remote bases.
"Rolls-Royce plan to have a reactor ready to send to the Moon by 2029". With that deadline I would expect something closer to a proven submarine reactor adapted for an environment without abundant water and fewer convenient ways to get rid of heat.
Since RR make submarine nuclear reactors for the UK's fleet already, yes.
Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#137It will be interesting to see a modern design, rather that the something based on 1930s physics, 1940s construction methods, built in the 1950s and put into use in the 1960s like some of these military reactors they used for remote bases.
No matter the design, it’ll be built by lowest bidders around the world. /s
Clearly you have never heard of cost plus contracts.
Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#138Earlier quoted context omitted.
Once you're on the surface you can sink a fair bit of heat into the ground. The issue in space is that you can't do convection, and there's nothing to conduct to, so you're really just left with giant, inefficient radiators.
Nitpick: Are radiators very inefficient? I assume they're 100% efficient, just not very effective due to the limits of physics.
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Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#139Earlier quoted context omitted.
NASA did a study in the 1980's. For something more recent, I suggest checking out Dr. Casey Handmer. https://ntrs.nasa.gov/api/citations/19830007081/downloads/19...
Wow awesome thank you!
It's a super-specific niche that I'm very interested in but sadly has very little activity, so I'm happy to spread the word. ISRU "in-situ resource utilization" gets a bit more press more and then.
Isaac Arthur also has some good episodes (video/podcasts) on the subject of bootstrapping off-Earth industries like on the Moon or asteroids or Mars.
Re: UK backs Rolls-Royce project to build a nuclear reactor on the moon
#140Earlier quoted context omitted.
Heat will be an asset, not a problem: the Moon sub-surface temperature is around -20C ([1]), which means there's an easy way to dissipate power. And if we have any humans living on the moon, that heat will very much be appreciated around all livable areas. https://space.stackexchange.com/questions/19906/constant-lun...
I don't know if that will cool the reactor enough to prevent a meltdown.
Cooling a gigawatt-class reactor like that? - not a chance
A 10kW reactor - easily; a very limited amount of engineering to design a heat distribution system will be required, but 10kW is also not enough for anything useful.
I suppose the future of Moon energy will be in megawatt-class reactors, which are still possible to cool like that, but provide enough heat+energy to be useful for colonies.