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?

  • 1
    $\begingroup$ 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. $\endgroup$
    – Mike H
    Commented Sep 24, 2017 at 5:34
  • 3
    $\begingroup$ 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... $\endgroup$ Commented Sep 24, 2017 at 6:45
  • 2
    $\begingroup$ @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. $\endgroup$
    – SF.
    Commented Sep 24, 2017 at 11:01
  • 1
    $\begingroup$ Lets make that a perceived risk creating the PR nightmare. These things are build pretty study. $\endgroup$
    – Hennes
    Commented Sep 24, 2017 at 15:29
  • 3
    $\begingroup$ 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 - 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. $\endgroup$
    – kim holder
    Commented Sep 25, 2017 at 4:14

4 Answers 4


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.


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)


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.


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.


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.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.