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I've been trying to come up with a scenario in which space stations and lunar bases are established but are considered controversial. I sort of figure that if corporations started mining the moon that some people would start freaking out about it having an effect on Earth despite the fact that the moon would have to be extensively mined before it had any real effect on things like the tide.

My question is that given roughly a hundred years to account for improvements in space transportation and nuclear energy would the mining of the moon for helium 3 for use in fusion generators possibly be profitable enough to justify the cost and risk?

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This isn't a perfect source but Charles Stross includes Lunar He3 mining in his list of scifi-bunk.

http://www.antipope.org/charlie/blog-static/2015/12/science-fictional-shibboleths.html

Short answer: No. There's better materials to do fusion with.

Now for a biggie: Mining the lunar regolith for Helium-3. This is junk science on stilts and it just keeps coming back from the dead. It's also a barrel of past-their-sell-by-date red herrings that keeps being rolled out by space cadets whenever they're challenged to produce an economic justification for space colonization. Here's why it's crap ...

Fusion, the Jenga-pile begins, is the energy source of the future. (This may or may not be true: I for one hope it is.) However, the easiest form of reaction you can run in a fusion power reactor is deuterium/tritium. This tends to release most of its energy in the form of neutrons, which can ideally be captured and used to breed more tritium fuel and produce waste heat to drive a turbine generator. The problem with neutrons is that they're rather penetrating and when they slow down enough to be captured by an atomic nucleus they transmute it, often into an unstable isotope. D/T reactors therefore look likely to suffer from one of the same problems as fission reactors: neutron-induced structural embrittlement and secondary activation producing high level radioactive waste.

Aneutronic fusion—which hasn't actually been tested yet in even a prototype research fusion reactor—offers the possibility of running on other fuels and producing <1% of its energy output in the shape of neutrons. Helium-3, an isotope of helium consisting of two protons and one neutron, can in principle be fused with deuterium instead of the (radioactive) tritium and produce power with a far lower neutron output—the energy-bearing product of the reaction is a proton, which can be contained using magnetic fields. Hence the interest in He3 fusion reaction designs.

The first problem with He3 reactors (after—cough—we don't know how to build one yet) is that He3 is incredibly rare. It costs on the order of millions of dollars per kilogram and the global supply is very restricted; there's certainly not enough of it to power a global energy economy even at today's levels. But there is some evidence that He-3 produced in the sun and emitted in the solar wind may be captured in the Lunar regolith. The plan, per the proponents of lunar colonization, is therefore to build vast strip mines on the moon to extract this vanishingly rare moonshine/pixie dust and export it to Earth to power our 22nd century energy economy. And of course estimates that we could power our current level of energy use by processing 4 million tons of lunar regolith per week are music to the space cadets' ears because, well, it means big engineering and thus big steely-jawed engineers with slide rules and socket wrenches on hand to repair the mining machines when they break. Space colony justified!

Except this is moonshine and junk. Firstly, we don't have an aneutronic fusion reactor, much less a planetary base load capacity driven by aneutronic fusion reactors in need of fuel. Hell, we don't even have a working D-T fusion reactor that can produce surplus energy; ITER isn't due to achieve first plasma until 2020 and won't begin D-T reaction operations before 2027, and the Wendelstein 7-X, while promising, is a generation behind (roughly equivalent to where the Joint European Torus was in the 80's).

But let's jump the gun. Let's assume we do have a working fusion reactor. Let's even assume we've put in the decades of legwork required to build a working aneutronic fusion reactor—it's worth noting that aneutronic reactions have to run about an order of magnitude hotter than D-T fusion reactors can achieve, and they're already in the 100 million Kelvin range. But let's play make-believe: are we then going to see large-scale lunar regolith mining to fuel the beasts?

Nope.

Because it turns out that if you can build an aneutronic reactor, then, subject to some considerable amount of fine tuning, you can run it on fuels other than sparkly lunar regolith moonshine and pixie dust—notably the proton-boron-11 cycle and the proton-lithium-7 cycle. Both these fuel cycles are aneutronic and run on isotopes that are readily available here on Earth in sufficient quantities to power our civilization for some millions of years without trying to build massive engineering infrastructure on an airless rock. There's even an aneutronic fusion cycle that relies on proton-nitrogen fusion, although it produces less energy and is even harder to achieve. Nitrogen and hydrogen ... nitrogen makes up about 80% of our atmosphere, and hydrogen makes up about 15% of our hydrosphere, so we're not running out of either of those fuels any time soon, either.

Upshot: any work of SF that takes "Lunar 3He mining" as an economic premise is about as plausible as one that assumes combustion powered by the release of phlogiston.

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  • $\begingroup$ Even if you grant that 3He is the ideal aneutronic fuel, there is also the issue of boiling out of lunar regolith, which will be pretty energy intensive on its own..... $\endgroup$ – Thucydides Mar 9 '16 at 3:25
  • $\begingroup$ I guess maybe it could be useful to fuel power plants on the moon if you already had a lunar colony for other reasons. $\endgroup$ – user867 Mar 9 '16 at 6:56
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Nobody really knows.

First, the high value of He3 assumes commercial scale nuclear fusion. This is probable, but unknown. We could in theory cover our needs with solar IIRC. And there are still some unsolved issues with fusion power. Although cleaner He3 fusion would help.

Second, the full costs of lunar mining are unknown largely because the exact method that is best for doing so is unknown. For example, would we need to establish an actual moon colony or could robots with remote oversight from Earth handle it? My guess would be that eventually the development of technology will push costs down enough. But obviously the costs also depend on the volume of the demand which depends on the proportion of power that comes from He3 fusion. Which depends on what other energy sources we use and how much.

Third, we might find a cheaper source of He3. It is not strictly speaking true that it doesn't exist on Earth. Thermosphere and exosphere, the highest layers of atmosphere, do have solar wind derived Helium as a component. Extracting it from there might be cheaper than lunar mining.

That said, it is considered likely, since at the moment it seems the value of He3 will go up and the costs of lunar mining will go down in the future.

Certainly, if, to pick an entirely random example, China would want to go to the moon as a prestige project to prove its super power status, mining He3 could be used to pay some of the costs. Similarly the development of the necessary mining technology would have value of its own. So strictly speaking it might not be necessary for it to be profitable enough to pay the full cost.

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Absolutely, if you want to power things on the moon.

While transporting things from the Earth to the Moon might not be terribly expensive, given the limited depth of the Moon's gravity well, transporting anything from the Earth to the Moon will break the bank. With the development of fusion power, it would make far more sense to mine helium on the moon for use in your nuclear reactors.

There's a major reason to want to power things on the Moon, as well: it's far cheaper to get things into orbit around the Earth if you start from the Moon. If people are serious about building orbital platforms, spacecraft, and the like in bulk, exporting the entire manufacturing process, from ore mining through final fabrication to the Moon could result in huge savings.

If you're already mining it on the moon, it would almost definitely be worth exporting to Earth.

Once you've got a diversified mining industry in place on the Moon, it would almost definitely be worth exporting that Helium to Earth. The Moon's gravity well is shallow enough that you could easily launch capsules to Earth using a large gauss gun firing tangentially to the Moon's surface. That would probably be your main expense, given that packaging and parachutes could be constructed from Lunar materials and fabricated on the Moon.

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  • $\begingroup$ I agree, I kind of touched this at the end of my answer, but it didn't occur to me that it would be an answer by itself. $\endgroup$ – Ville Niemi Mar 8 '16 at 5:08
  • $\begingroup$ About exporting the He3, it would be extremely easy to make a railgun on the moon to send raw resources on earth. If you already have a fusion power plant, no problem to power the gun. $\endgroup$ – Madlozoz Mar 8 '16 at 13:56
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Based on really basic estimates, I found that helium 3 has an approximate value of $1050 per liter based on this Wikipedia page. Assume the mining operation costs about 1 trillion USD per year to set up and maintain on the moon. According to this page,

As a result, it has been estimated that there are around 1,100,000 metric tonnes of helium-3 on the surface of the Moon down to a depth of a few metres.

This gives us an approximate value of 997903214 liters of dry helium 3 on the moon's surface. Using the \$1050 figure we calculated earlier, the profit of this system yields \$1047798400000, or 1047798.4 trillion USD. (This all, of course relies on whether the US is the only country mining this valuable resource).

Also, you don't specify how safe the system for mining is, so I won't make any guesses there, but to me, this system seems well worth it.

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    $\begingroup$ \$10 billion/year is too low. This study put the cost for a manned base at \$35 billion plus \$7 billion/year to operate. That's just to support a few people and scientific equipment. A mining operation would require sending far more mass and infrastructure for mining and processing, not to mention launching the helium back. $\endgroup$ – Schwern Mar 8 '16 at 4:55
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    $\begingroup$ One would think that the price per liter would decrease if a billion liters were put onto the market $\endgroup$ – Kys Mar 8 '16 at 16:31
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See G. Harry Stine's "The Third Industrial Revolution" It's quite dated, but conceptually it will be of benefit.

The answer is not He3, but rather just mass. Stine advocates solar power, and microwave links back to earth, build by factories at the Earth Moon leading and trailing Lagrange points. It requires a reusuable heavy lift launcher for bootstrap purposes. The Rand Corporation figured about a trillion spent over 20 years for the infra-structure (1975 dollars) then GW solar units at a couple billion each. Units would link with feedback phased array microwaves. Ground antennas would be about 10 miles across but the power density is low enough that you can still use the area for grazing.

Jerry Pournelle and Ben Bova have novels set in this style of future with somewhat different outlooks on the economics.

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