The Economic Development of the Moon

MarkWhittington writes "Andrew Smith, the author of Moondust: In Search of the Men Who Fell to Earth, recently published a polemic in the British newspaper The Guardian, entitled Plundering the Moon, that argued against the economic development of the Moon. Apparently the idea of mining Helium 3, an isotope found on the Moon but not on the Earth (at least in nature) disturbs Mr. Smith from an environmentalist standpoint. An examination of the issue makes one wonder why."

Comments

A lot of dirt, not much helium-3

[iamlucky13]

A lot of us are anxious to see some major commercial application of space (see the recent discussion on space-based solar power, too), but I'm afraid helium-3 mining on the moon is not a feasible one.

First of all, Helium-3 already exists in smaller amounts on earth. It makes up about 0.00138% of the helium on the earth, as opposed to 0.00138% of helium on the moon. More importantly, it can also be synthesized by deuterium fusion or by tritium decay, although current production is only a few kilograms per year. However, one of the first generation fusion fuels is deuterium, so it's very likely that first generation technology could eventually be used to make fuel for second generation fusion plants.

Second, obviously, we have not achieved practical hydrogen fusion yet, much less helium fusion, which is harder. The current ITER timeline estimates the first commercial hydrogen fusion plants will come online around 2040-2050. Helium fusion, if we decide it's worth the effort to develop, will come later.

Third, you have to move a lot of dirt to get a useful amount of He-3. Estimates are the US alone would need at least 15-20 tons per year for our current electrical generation. At the quoted 0.01 ppm on the moon, that means you need to process 2 billion tons (approx 670 million cubic meters) of regolith every year. In comparison, the giant Three Gorges Dam in China required excavating only 134 million cubic meters of material over a period of 10 years, using thousands of workers and who knows how many tons of heavy equipment.

Additionally, processing the regolith for the helium requires first boiling out all of the gasses by heating the excavated dirt several hundred degrees, then separating the minute fraction of He-3 from all the "waste" gasses. It will be very energy intensive. By my very rough math, every cubic meter of moon you excavate requires on order of 100 kW-hours of heat, so a year's worth of digging would take 47 billion kW-hours. This is about 4% of our current electrical usage, which hints at the scale of the power production facilities that would have to be built on the moon to facilitate this mining...over 5,000 MW of capacity not counting digging and gas segregation energy needs.

Not for mining, for launch

[Animats]

The "Helium 3 on the moon" people have it backwards. As someone else pointed out, you have to mine a lot of dirt to get any useful amount of the stuff. On the other hand, deuterium is available at moderate prices. Heavy water costs about $300/Kg. If we ever get fusion to work as a power source (a big if, after half a century of failure), deuterium fusion will work first.

There's some grumbling about deuterium fusion producing radioactive waste products, but it's nowhere near as messy as fission. You get some tritium (which is a useful material; among other things, it decays into ... Helium-3!) and the reactor components may become radioactive, but the isotopes are relatively short-lived; decades, not millennia, of decay time are required. The concrete and steel has already cooled off for many older decommissioned reactors.

Helium-3 fusion is potentially cleaner, though. If we ever get fusion to work, it's the fuel of choice for getting off the earth with fusion power, because you could dump the reaction products into the atmosphere without causing fallout.

So forget about mining the moon to power Earth. Dumb idea. Think about mining helium on Earth to power launch vehicles.

Re:Wonder and amazement

[Waffle Iron]

Serious mining can move serious amounts of material in a short time, and if the moon became Earth's primary source of material for power, I suspect we'd make a measurable impact within decades.

We're talking about fusion fuel here. Worldwide energy needs can be provided by a few thousand tons of fusion fuel per year. So with the moon's total mass of almost 1e20 tons, it would take hundreds of times the age of the universe to make any significant impact on tides.

But don't worry, it's not going to happen anyway. To harvest usable amounts of the trace quantities of He3 on the moon, we'd have to remotely mine and process countless gigatons of lunar dust. This would be an operation that dwarfs coal mining on earth, but be thousands of times more expensive to carry out. It would almost be certainly easier and cheaper to develop boron/hydrogen fusion technology here on earth, or deal with the drawbacks of simpler deuterium/lithium fusion technology, than to undertake this outer space pipe dream.