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Has there been any research on what lunar in-situ processes would have to be developed to mine and process thorium to build nuclear thermal rockets on the Moon?

kim holder
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jjossy
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    Why would you bother. It would be far less effort to source fissile materials on earth. Save lunar mining and processing effort for those materials required in large quantities. – Mike H Sep 24 '17 at 05:34
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    Building on @MikeH's comment, lunar thorium is about 5ppm in the concentrated areas (see doi:10.1029/1999JE001103.) There is about 6ppm in Earth soil per WP. Not only is it easier to build infrastructure here, the raw material is equally abundant... – Andrew is gone Sep 24 '17 at 06:45
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    @Andrew: Politics and risk of carrying a nuclear reactor on top of a stack of explosives through the atmosphere. The lunar thorium would save the PR nightmare (and actual risk) of contaminating Earth with a failed launch. Bring an interplanetary craft with empty NTR engine to LEO from Earth, bring fuel (even using NTR propulsion!) from the Moon, fuel up in LEO, fly the manned craft anywhere, return the fuel carrier to the Moon. – SF. Sep 24 '17 at 11:01
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    Lets make that a perceived risk creating the PR nightmare. These things are build pretty study. – Hennes Sep 24 '17 at 15:29
  • Perfect SF. Thank you. This is exactly why I asked the question. @Hennes: There is no PERCEIVED risk of a PR nightmare. ITS REAL. Keeping it as civil as possible: there is a large population of well-intentioned environmental activists that will fight this tooth and nail. So launch a pack of self replicating robots programmed for in-situ processing of lunar regolith and build the nukes on the Moon. Is it feasible in the regions on the Moon with high concentrations of Thorium? – jjossy Sep 24 '17 at 20:47
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    Well, hello, jjossy. But the actual risk of a failed launch is minimal - the radiation would be completely inconsequential. That i got from the answer to a question of mine on the matter - https://space.stackexchange.com/a/16609/4660 . If all you are carrying is fuel rods that have never been used, they really aren't very radioactive. – kim holder Sep 25 '17 at 04:14
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    @Hennes: Even if it's sturdy enough to survive RUD on the launchpad, If the second stage explodes at around 7km/s there's no way the reactor would survive reentry. – SF. Sep 26 '17 at 22:41
  • I seem to have communicated unclearly. I agree there will be protest. Those will be about a perceived risk. And we can make that risk negiable, but only at the cost of extra mass. At which point it might be more economical to get it elsewhere. – Hennes Sep 27 '17 at 15:49
  • Thanks Kim. I'll let you explain this to the environmentalists and I'm sure they'll have no problem with it. Just don't use the term "nuclear" in your description! :) – jjossy Sep 27 '17 at 17:39
  • @Hennes: The necessary amount of extra mass would be so expensive as to make this means of propulsion completely pointless (take same amount of plain old chemical propellant instead, get better delta-V). You need to shield the reactor against a massive explosion followed by reentry. That means strong, good heatshield all around, parachutes to reduce speed of impact, and that all wrapped in a shell that will withstand RUD (but getting damaged by it, becomes worthless as heatshield and needs to be discarded). – SF. Sep 29 '17 at 12:53
  • @SF. It's fairly common to launch radioisotope thermoelectric generators into space. For example, Cassini-Huygens had about 33kg of plutonium on board, and lots of others have also been launched. – David Richerby Sep 29 '17 at 19:59
  • All, thanks for contributing to this thread. To clarify, my purpose in starting it was to source thorium on the Moon for nuclear thermal rockets which Kim uses in her scenario (www.moonwards.com). Nuclear rockets are bugaboo in Earth's biosphere. The idea was to build them on the Moon for use in space, not on Earth. I need someone who knows the processes for mining thorium and refining it to make nuclear fuel rods in-situ on the Moon....and all the other needed processes for Kim's nuclear rockets. Regarding RTGs, does anyone remember the howls of protest when Cassini was launched? – jjossy Oct 01 '17 at 00:15
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    Side note @jjossy: We don't really have self replicating robots yet. – Daniel Jour Oct 01 '17 at 14:10

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Mining lunar thorium gains you nothing. Thorium is not fissile and cannot be used to fuel a nuclear rocket, power plant, or RTG.

Designs for "Thorium" nuclear power plants use thorium as a fertile material to breed fissile U-233 using the neutrons from a fission reaction fueled by fissile U-235 or U-233. You start with a fairly conventional U-235 fueled fission reaction, use surplus neutrons to breed U-233 from a fertile thorium blanket, and eventually you have enough U-233 to power your core reactor and you are no longer reliant on U-235. It's a breeder scenario that is attractive to many because it ends our dependence on U-235 among other reasons.

So to use lunar thorium for a NTR, you need to ship enough fissile (and radioactive) U-235 to the moon to fuel a fission reactor, which you must also build there, operate the reactor with a thorium blanket, chemically separate out the resultant U-233, and then process THAT into NTR fuel elements. You're launching a large quantity of radioactive U-235 as the first step in a very expensive process in making something very similar to U-235.

Kengineer
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There are other considerations like the fact that you might take thorium from the slag after reefing aluminum, magnesium, iron, oxygen, silicon and hydrogen(if you go polar). There are other materials but these are the main ones I remember. And that there maybe someplace with better thorium concentration than earth.

That said at the start of actual mining on the moon, a theoretical process that we are only beginning to explore would be very expensive. Mine 1000 ton for 5 kg of thorium. With very limited resources on people, and chemicals to separate the components. After all even aluminum is not so easy as iron to melt and most of the unwanted things go away. And aluminum is not even the most difficult metal to extract from regolith, or any natural resource. That is usually not something you really think about. You just imagine melting everything, but industrial process are rarely so simple and we just begun to actually experiment to try doing it differently than how it works on earth.

If we manage to get a facility running that main consideration would be the capital cost and the people working there. 1 astronaut send to the moon should cost about USD 50milion at 10kUSD/ kg along why a year of supplies considering bulk cost. At 5PPm if this person alone can maintain a station that refines 1000 tons a day the Gross profit from selling the 5 kg of thorium should be about 25k USD or 9 million USD a year. So 18% of the cost of sending the astronaut there. And this is considering this single person can manage from extraction to refinement.

With a very high level I suppose that those would not be impossible just very hard.

Sending thorium up is not all that expensive in the grand scheme of things even if you would need a special container that can survive reentry massively overbuild made of pure metal so even if the whole thing exploded or were directly hit by a small Kinect penetrator it would survive. You don’t really need to worry that much.

Also a kg of thorium has about 80.000.000 MJ(+-10% I doing from memory) or 1,02MW for 2,5 years. Much more than the ISS, enough for an ion/plasma engine going somewhere in the solar system.

So extract a metal that we at the moment we have a surplus on earth and would need to send in small amounts in the foreseeable future from a far place. Not really smart. Little to no demand, high cost, high initial investment. (machines than can mine and refine 1000 tons of ore a day. Plus massive amounts of power for the refinement.

In the future when we are mining the moon for Oxygen, silicon, aluminum. It may make sense to develop technics to also extract thorium, but at the moment there is absolutely no reason except maybe to learn how to do it and develop better new thecnics of refinement suitable for space.

(I’m not native so my English is a bit skewed)

OuNelson Mangela
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It might be worth it to mine thorium on the Moon. The comments have indicated the political costs of shipping it from the Earth (and we'll likely need it down here anyway).

The risks of launch can be minimized by increasing the mass you are launching which starts to explode the cost of launching out of our gravity well.

I have no information about the cost of mining thorium on the Moon but it will all depend on how much you need up there. At some point, shipping the proper refining equipment will cost less than shipping continuous quantities of thorium.

Notice that I said "refining" in the above paragraph. It makes sense to mine once and refine as many minerals out as you can.

ShadoCat
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You'd have to ship all the mining, refining and processing equipment (all of which is heavy and requires lots of energy and strong either strong acids, alkalis or oxidizers) to the Moon.

https://www.britannica.com/technology/thorium-processing

You've got to crush it, filter it, and then either:

  1. dissolve it in hot, concentrated sulfuric acid and then nitric acid, or
  2. dissolve it in hot sodium hydroxide, or
  3. reduce it with fluorine.

None of this is cheap, all is dangerous and all requires a heavy industrial infrastructure that would all have to be created on the Moon.

RonJohn
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