Mine The Moon For Helium-3
Posted by timothy on Wednesday January 21, @05:13PM
from the imperative-voice dept.
Rob Kennedy writes “A story at The Daily Cardinal is reporting that UW-Madison researchers are looking to mine the moon for helium-3 as an energy source, which supposedly would yield about 1000 times more energy per pound than coal. Although there are several hurdles that would need to be cleared, The Associated Press mentions one catch in particular: ‘The researchers still are working on building a helium-3 reactor that would produce more energy than it takes in.’ Indeed. SciScoop has a more in-depth discussion of the prospect.”
Very informative comment off of SciScoop by RickyJames
Kulcinski and FTI have presented a graduate course entitled “Resources From Space” in 1996 [wisc.edu], 1997 [wisc.edu], 1999 [wisc.edu] and 2001 [wisc.edu], taught by a variety of instructors including Harrison Schmitt. Each of these have extensive notes and pdf files online, and probably are the best sources for data on the Internet on the topic of using lunar resources for energy. These two guys are the leading proponents of helium-3 use; if anybody is going to make a good case for this, it’s them.
The key factor is the dilute nature of the helium-3 in the lunar regolith, and all the other stuff that’s mixed in there with it. Schmitt estimates on page 19 of lecture 10 in the 2001 course that the He3 abundance is “up to 30 ppb” or 30 parts-per-Billion-with-a-B in the top 10 feet of lunar soil. Also embedded in the lunar soil is 30-180 parts-per-Million-with-an-M of hydrogen and 30 parts-per-Million-with-an-M of normal helium or He2.
So, say you want a ton of helium-3 from the Moon. You’ve only got to do two things.
Step one, heat up 1,000,000,000 / 30 = 33,333,333 tons of lunar soil. That’s a lot of dirt and a lot of heat. All of the hydrogen and helium gas in the soil is baked off and captured. You get 2001 tons of hydrogen and helium – 1000 tons of hydrogen gas, 1000 tons of helium gas, and one ton of helium-3 gas.
Step two, you’ve got to separate the ton of helium-3 you want to ship back to Earth from the 2000 tons of normal helium and hydrogen you don’t. Getting the hydrogen out is relatively easy; just combine it with lunar oxygen to make water. Try to avoid a titanic explosion in the process. Separating that one-in-a-thousand helium atom you want from the helium that’s left, though, is hard. It’s the same problem faced with the Manhattan Project people trying to separate the U-235 uranium atoms that could make a bomb from the U-238 uranium atoms that couldn’t. You’d have to recreate wartime Oak Ridge isotope separation plants on the moon – and those aren’t going to be built from lunar material, I assure you.
As a point of interest, coal strip mines in the West get out 25 tons of coal for ever manhour of labor used. By this criteria digging up 33 million tons of moondirt per year would take 1.32 million manhours of labor. At 2000 manhours per year, that’s a required crew of 660 miners for one ton of He3 per year.
You say we need 30 tons of He3 per year – that’s the equivalent of 20,000 miners moving as much moondust around as the entire U.S. coal mining industry mines in coal in a year. I know, I know – the situation isn’t comparable, NASA would create a super-automated unmanned bulldozer fleet, etc. etc. Running on what? Costing what? Getting to the moon how? None of these are impossible factors, only impractical ones.
Then, there’s the question if a fusion reactor could ever be built that would use helium-3. Sure, it sounds good. But we haven’t even built a deuterium fusion reactor yet, and the physics of that is a LOT easier than getting a helium-3 reactor to work. In the 1950s fission reactors were going to be cheap and simple, too. Remember “electricity too cheap to meter”?
I dunno, Sylvia. It sure sounds good to say, here comes this shuttle with a one ton can of helium-3 on board back from space that’s landing on the runway to solve all of our problems (for two weeks – you need 30 tons per year, remember?), wave the flag and strike up the band. But when you look at what it takes in infrastructure to get that helium in the can on the moon, and what kind of infrastructure you’re going to pour it into once the can is offloaded and the band’s gone home, well, it’s just not quite so attractive to investors. Especially as long as they know they can easily scrape coal off of surface mines in the West and easily poke holes in the ground in the Arabian penensula for the next 500 years and KNOW coal and oil is going to be there.
And it will. We’ve got plenty of coal and oil to last for centuries, and plenty of conservatives who say global warming and greenhouse gases are liberal myths. Potentially dangerous combination.
AP, I know you’re going to read this – referee me here, keep me honest….