Note - the following is the result of me sitting down and doing some back-of-the-envelope calculations. I may be off on some of my figures or math. If you have any corrections or comments, please post them.

Helium-3 mined from the moon has gotten some attention lately as a fuel
source for future fusion reactors. It would take as little as 25 tons of
He3 to satify the annual current energy needs of the united states - a
quantity which could be carried in a single shuttle mission. We don't yet
have reactors which can burn He3, or a shuttle-sized vehicle capable of
bringing such a load back from the moon, but these are things we should be able to develop in the future. So it sounds like a good idea, right?

I decided to run some order-of-magnitude calculations to look at the
economic feasability of the project. The results suprised me.

In order to understand the economic rational for mining He3, we have to
look at what makes it a desireable fusion fuel. For economic feasability
we have to look not just at He3 but compare it to alternative power sources. Deteurium-Tritium fusion is the easiest form of fusion we are likely to use as a power source. It occurs at a temperature lower than any other fusion, releases a lot of energy per reaction, and we will never run out of fuel for it. The downside is that much of the reaction energy is released in the form of fast neutrons. Converting fast neutrons into electricity is inefficient, and the reactor walls will suffer neutron embrittlement and need periodic replacement, generating a steady stream of highly radioactive waste.

He3 fusionis more difficult to achieve, taking about twice the temperature,
and releasing less energy per reaction. On the plus side the reaction is
nearly aneutronic (the He3-D reaction releases no neutrons, but some D-D
reactions will also occur, releasing some fairly low-energy neutrons) and
the energy released can be converted into electricity at higher efficiency.

So, the question is, is extracting He3 from the moon cheaper and easier than dealing with the radioactive waste products from the D-T reactors?

He3 is present in the lunar soil at a concentration of about 1 part in
200 million. Extracting 25 tons of He3 means that your lunar extraction
plant will need to process a whopping 5 billion tons of lunar material
annualy.

To extract He3 from lunar ore, we need to scoop up the material, sift and/or crush it to break up the clumps and rocks, bake it in an airtight oven for a while, seperate out the He3 from the other gases released, and then dump the spent lunar ore somewhere it won't get in the way of your continuing operation.

To estimate the cost of building and running the extraction plant, I looked
at existing stripmining equipment used on Earth. Lunar equipment will
operate on similar principles, although of course many of the engineering
details will differ. Lunar equipment operates in 1/6 earth's gravity, so
the structure can be lighter. On the other hand, lunar mining equipment
will have to be self-powered. For the purposed of this essay I'm assuming
that all of the mining equipment is solar powered. The other option is
nuclear power - but manufacturing so many nuclear power plants will
generate more radioactive waste than we save by using He3 fusion, so that option is a non-starter.

Being solar powered means the equipment can only operate during the lunar day. For simplicity I assume that we can get 4000 hours of operation out of our lunar equipment per year. I'll also ignore breakdowns and downtime for maintinence.

Lunar equipment will also need to deal with severe monthly temperature
swings. Heavy mining equipment will need liquid-cooled radiator loops to
keep from overheating during the lunar day, and will need to be kept from
freezing during the lunar night. The lunar equipment in this example will
also need to be able to operate for years, autonomously or remote
controlled at best, with little to no maintinence.

For the first step, gathering the ore, I looked at bucket-wheel excavators
used in strip-mines. A good bucket-wheel excavator can dig up about 8 times its own weight in ore an hour. For this thought experiment I'll assume our self-powered, self-contained lunar soil excavator can scoop up 10 times its own mass per hour.

Secondly, the ore needs to be transported from the excavator to the
processing plant. Modern mine trucks can carry nearly twice their own
weight in ore. Lunar mine trucks should be able to beat this. I will
assume that our transport system can carry 20 times its own mass of ore
from the excavator to the plant per hour.

Then the ore needs to be sifted and/or crushed. Fine powder is going to
more readily heat up and release He3 - putting rocks and bolders into our
ovens is a waste of time. Earthly crushing plants can handle anywhere from 2 to 8 times their own weight of rock per hour. I'll assume our lunar
processer can crush and/or sift 10 times its own mass per hour.

The ovens to heat the ore will probably use large mirrors to concentrate
sunlight on the material. The oven chamber itself needs to be airtight,
to keep the scant quantities of He3 from escaping. The low-pressure gases given off from the ore need to be pumped out into a seperation system to extract the trace He3 from the other gases released. Some of the other gases may also be useful for local use, such as oxygen for a manned lunar settlement.

I don't have much to go on to estimate the mass of the solar oven. 10 times its own mass of ore per hour seems like a reasonable quantity.

Finally the spent ore needs to be carted off and dumped somewhere. Again, assume lunar ore trucks can transport 20 times their own mass per hour.

On top of the ore-handling equipment, you'll probably need centralized
control and communication systems, mapping gear and location beacons, a storage yard for spare parts and repair vehicles to put them into effect,
and finally a system to transport the refined He3 back to Earth.

Looking at our target numbers of 25 tons of helium per year, and 4000 hours of working daylight per year, we see that our lunar He3 plant needs to process 1,250,000 tons of lunar ore per hour. Adding up the masses of the required equipment above, we can see that setting up a lunar processing plant to provide our yearly needs of He3 will mean sending over half a million tons of equipment and supplies to the moon. That's rather a lot. Using a rough figure of 40 million per ton of payload delivered to the moon, it will cost over 20 trillion dollars just to send the He3 collection system there. That's not counting the costs to build the hardware, or to support and supply it once in operation.

I submit that we can deal with the nuclear waste generated by D-T fusion
plants for much, much less than 20 trillion dollars.

There are probable more efficient ways to do the He3 extration than the
method I outlined above. But even if you can find a way to do it at ten
times the mass efficiency, that's still 2 trillion dollars to get it there.

Now, it may be that we'll someday develop a way to put things onto the moon for a fraction of today's prices. Or perhaps we will have a large lunar base, with a massive mining operation to produce oxygen and metal alloys for local operations, and the He3 will be a welcome by-product. My point is that if my assumptions and math are correct, with today's technology the cost of building the industrial infrastructure required will make the project economically unfeasable.

And by the time we can afford to build this kind of system, we may have
better options for energy. Hydrogen-Boron fusion looks to be very hard
to achieve, but is also clean and uses fuel that we have here on earth in
effectively unlimited quantities.

Yes, I get very annoyed at glib Lunar He3 mining stories. We don't know if or when He3 fusion reactors will be technically and economically feasible, regardless of the price of He3. It certainly will be several decades AT LEAST. And there are many unknowns about lunar He3 mining.

Well, there is plenty of deuterium. Tritium must be produced by transmutation of Lithium 6 with neutrons. A "Lithium blanket" is another feature that supposedly would be present in a working D-T reactor, but is still largely undeveloped. Incidentally tritium will decay to He3, so if a lot of tritium is produced, it could be a source for some He3-D reactors.

Yes, let's be clear that we aren't even close to a commercially useful fusion reactor or ANY sort. Also, while the reaction would be low on neutrons, it is by no means "radiation free." I expect the strong anti-nukes would not be satisfied. While there would be great design advantages, there would still be reactor erosion issues due to the extremely hot plasma.

The tougher requirements for D-He3 fusion would probably add decades to the time it could be feasible.

Or what about technology we have today? That is, conventional fission reactors. I'd like to see more work done in refining fission technology - my preference would be to move to passively safe high burnup reactors. THAT we can do. One of the sad things about the cutoff in U.S. commercial nuclear development is that current reactors are largely unchanged from '60s designs. Not that they are bad, but there is room for improvement.

I agree on the time scale issue - it just doesn't make sense to be talking about something as unproven as He3 fusion today, and time will change the rules. On H-B11 fusion: This is a LOT harder to achieve. In a magnetic confinement system there would likely be huge bremsstrahlung losses. It is also a relatively low energy reaction, so breakeven would be very difficult. It would likely take an absolutely huge reactor (possibly a single reactor that could produce a good fraction of current total power production) or a novel design.

My hunch is that, if He3 does become important, we'll get it from Uranus. It has a lower escape velocity than Jupiter, Saturn, or Neptune and there is a lot of helium in the atmosphere.

I am really anti-all-this-lunar-mining-thing [-X. We should preserve the moon, it's an amazing piece of natural art. A few footsteps, a flag and a monument is more than enough . It should be a natural reserve park.

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So, you want to make a sterile rock with no life whatsoever on it a nature park?

This mindset I just can't agree with. We'd still be hiding in caves if our ancestors had thought this way.

I have no objection to mass mining of the moon in principle. It's just that there's really not much there worth bringing back. He3 mining would become economically attractive if we could bring the cost of transporting cargo to the moon down by a factor of 1000 - assuming we also had working commercial He3 fusion reactors to burn it in. The raw minerals available on the surface of the moon are all things we have plenty of here on Earth - aluminum, titanium, magnesium, silicon, and other light elements. They'll be useful to lunar colonists some day, but unlikely to be profitable to send back here.

I wonder - since there's no atmosphere on the moon I assume these elements are in their pure form and wouldn't need much (any?) refining - so maybe in the distant future it would be worthwhile carting the stuff back from the moon instead of extracting it from their ores on earth...

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the solar system

They're not. Lunar metals are in the form of various ores, similar to low-grade ores on earth, which will require significant processing to make into useable metals. It can be done with materials available on the moon, but it's not just a matter of scooping the stuff up and melting it down.

If you really want to look at off-world metal mining, the asteroids are a much better bet. There are some nickle-iron asteroids which are nearly pure metal ore, and unlike the moon they have useful amounts of rare metals like platinum and iridium.

That was a very interesting, TinFoilHat. One thing people don't seem to realize is if someone does come up with a He3 reactor it would be far, far easier to use earth helium than moon helium. The concentration of He3 in lunar helium is only 10 times greater than in earth helium and is much more than 10 times more difficult to obtain. On earth helium can be obtained where it is trapped in natural gas deposits. Some natural gas deposits are up to 7% helium so there is no great shortage of it yet. If we wanted to could extract He3 from commercial helium today that goes into party balloons and scuba tanks and just hang onto it on the off chance He3 reactors become practical.

Good point. I think Hydrogen-Boron fusion is the future.

Excellent OP!

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- Learn a lot teaching others.

I totally agree, excellant OP!!

If the H-B reaction turns out to be the best, so be it. I will find another reason to go to the Moon, asteroids, planets. Uranus as a mining site, sure any excuse to go, or Titan for ethane/methane, Mars for iron. All these bodies are ours, we should use them wisely.

Dude, there's nothing there to despoil, its a barren rock. Its bombarded by more radiation than the Nevada desert, has less atmosphere than a yuppie coffee house, and no animals for PETA, WWF, or any of the other wounded hearts to bleed over.

Turn industry loose where there's simply no real damage to do other than to themselves.

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

Oh sure, then the nuclear waste dump on the moon blows up and sends it hurtling out of the solar system - none of us what that!

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At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009
All moderation in purple

Hey now, silver lining. Imagine all those dark sky nights with no full moon to compete with.

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

Re OP:
Thank. You.

Like Van Rijn, I never bought into the fantasy that He-3 is a valid reason to go back to the Moon, not when controlled, economical fusion *period* is looking more and more like a pipe dream.

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"Call me old-fashioned, but I think fire is magic. And it scares me a lot."

--The State

Even sterile rock still has beauty and value.

The Moon is highly visible everywhere in the world and has great cultural significance.

Uncontrolled lunar development will impact on other potential lunar activities - such as astronomy.

Space advocates dismissing people with environmental concerns as yuppies, wounded bleeding hearts, and other epithets is utterly unhelpful. It is reminiscent of the worst rape and pillage mentality of the 19th century of of for former Soviet Union. You want to win people over, not drive therm away.

Furthermore it is utterly unrealistic to expect there to be no controls over lunar development. There will be. There will be a need to reserve common resources (vacuum, solar power), not impinge on other users (astromers for example), and preserve natural beauty.

Jon

Heh, you'd think by taking mare regolith and covering the bright parts of it, you'd be doing them a favor.

However, lets be realistic. I am NOT talking about strip mining the surface here. That's not even practically possible to the extent that vast swaths of Lunar surface will be defaced, simply because its A) beyond the scope of modern technology even if we threw 100% effort into it, and B) not likely netting them anything useful anyway.

What I am talking about is if they do find something useful, turn them loose to get it. There's no water table to pollute, there's no atmosphere to choke, nor is there any native life to kill off. At worst, you end up with some localized devastation of the scenery, but you're talking about an astronomical body with several times the surface area of Eurasia. Most of what human technology is capable of doing won't be evident from anything other than a dedicated Moonsat like Clementine for decades or centuries at best. If its largely underground, we may never see it.

So spare me, poets, you're precious man on the moon has a long life ahead of him, even if we do industrialize it. If your panties are going to bunch up that much, there's the other 45% of the Moon you never get to see because of tidal locking, so we can always go crazy on the farside.

Heck, that might be worth doing, since it'll change the face of the New Moon phase as seen from Earth forever. To be able to look up at an otherwise dark patch in the sky, see a string of lights, and know we're out there, and out there to stay.

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

I was meaning lunar astonomers.

If we are talking about He3 mining (and I really like the cautionary note on this in the OP) then large scale mining is exacly what we are talking about. But your use of the word "deface" actually sets a useful limit. I can quite see an aesthetic limit on nearside mining that keeps it below visibility from earth, whether by naked eye or small telescope.

There are lots of ways of potentially degrading the Moon that would need to be avoided. The lack of atmosphere is something to be preserved, essential as it is for many astronomical and industrial purposes. Large scale surface mobilisation of dust would also need to be avoided. Another issue would be lwidespread contamination of the surface, especially if associated with dust molbilisation.

To be pedantic, slightly smaller than Africa.

Local devestation of the scenery is one thing. But large scale impacts are something else. Atmsopheric contamination may have potentially global reach Even the Apollo missions radically changed the composition and bulk of the lunar atmosphere..

ALso note that from a mining perspective, working underground is to be avoided, if possible. It is more complex, more expensive, and riskier. Also on the Moon its unlikely. The main resources are best extracted in the regolith - solar atoms, ilmenite, nickel-iron, oxygen, ices

Contempt for people with concerns is precisely the wrong way to go about it. You want to engage people, not alientate them. The fastest way to alienate a large segment of the population is to talk about lunar industrialisation in a way that looks purely in the short term and narrow economic focus. It will remind people of the worst of the 19th and 20th century. Industricl culture has moved beyond that, and trying to turn the clock back is counter productive.

IMHO of course. But I did spent over a decade in the mining industry, and allowing for multiple land use, stake holder consultation, rehabilitation, sustainability, and the triple bottom line have been part of mining in my country for several decades.

I have thought on this one, and it would be nice to see. But would it actually happen? how bright would the lights have to be? Could you see Earthly cities from the Moon with the naked eye, or a small telecope?

Jon

What do you mean by "large scale surface mobilization of dust?"

With no atmosphere, it is impossible for the dust to do anything other than follow a ballistic trajectory, and it would therefore be impossible to create any significant dust above the lunar surface...

Electrostatic repulsion!

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T. Anderson

It wouldn't take too much activity to give the moon a feeble atmosphere that could suspend dust. I don't know how much of an atmosphere you'd need, but it probably wouldn't be a great deal. After all, mars manages to do a lot with very little. It is possible that enough atmosphere to hold dust could result from frequent rocket use and industrial activity.

Even Apollo moved regolith fines more than a kilometer, exposed surfaces Surveyor 3 was sand blasted by Apollo 12. Larger spacecraft will move it much greater distances. This is not an insurmountable problem but will need management and consultation between users (preferably a head of time), not a laissez faire approach.

Other space environmental issues on the Moon that will need management will include light and RF pollution. You don't want spacecraft doing approaches over observatories, and the lunar farside is the quietest place in the solar system for radio astronomy. You don't want to waste that asset. Plus you don't want conflicting use of frequencies, or dangerous interference. Even on Earth, certain frequencies and use of electronic equipment are banned on mine sites beause of the risk of accidently setting off explosions.

Jon

Thank you, I was fishing for the right term in another thread and I flubbed it.

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

I have to agree. It seems to be terribly short-sighted to worry about polluting the Moon. Essentially what we're saying is, "no! please! For the love of god don't disturb the moon! Continue to destroy Earth instead!"

Don't people understand that a modest foothold on the Moon makes it possible to eventually move all your industrialization to some far away asteroid or something?? You have to get the foothold first though. If these people could actually stop us from industrializing the moon, then we never get that foothold, and we are ALL worse off in the long run.

This just seems like crazy talk to me. You could put every factory on Earth inside Copernicus crater and have room to spare. Are there really people who would object to that (if it were within our means)? Are there really people who would rather have a factory on Earth belching out pollution, so long as they can't see it??

In spite of the pollution caused by the industrial revolution, we are all better off because of it. We now have the wealth to talk about conservation. Imagine if such short-sighted people had been around in 1830 saying "whoa whoa! Not so fast! You can't build that factory until we work out ALL the possible consequences!" If that had happened in 1830 then you and I would be living on farms today, cutting down trees MORE than we do today to build our homes and heat our homes, we'd been poorly educated, there'd be no Internet, we'd all have at least 10 kids to help with chores. The world would be a terrible place! Can't you see that?

Strawman argument. Nobody is saying this at all. Just because we need to be responsible about how we act on does not mean that we are saying it is OK to be environmentally irresponsible on Earth. Quite the opposite. A culture than demands, indeed needs responsible beahviour on Earth will demand it oin the Moon.

People who think that all industry can be moved off Earth do not have the slightest idea of how economics actually works. There may well be space industrialisation eventually. But it will be in addition to terrestrial industrial activities, not instead of.

Again a strawman argument. Nobody is saying that they would rather have pollution of Earth than develop the Moon. What is being said is that lunar development requires guidelines and restains to ensure that the assets that make the Moon a desirable place for human activity are not squadered through short sightedness..

Straw man yet again. Nobody can work out all the consequences. But with a little foresight and planning some of the more obvious problems can be avoided.

Or do you really think that human activities should be carried out on the Moon without the slightest consideration to long term consequences? That waste gases should be vented regardless of the impact on astronomical installations and industrial facilities that rely on hard vaccum? That no consideration should be given to how dust mobilisation from landing and launch activities or mining might impinge on other uses of the Moon? That radio frequencies should be crowded with noise and chatter irrespective of the potential of the lunar farside to be the best place in the solar system for radioastronomy, or the hazards that uncontrolled RF uses can pose? Do you think there will be no controls on the use of lasers or plasma or ion beams?

Jon

Any waste gases from lunar industry could probably be collected for use in other processes. A waste product is just a resource we haven't found a use for yet.

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I'm all for moving heavy industry off the Earth. As I see it, there are plenty of rocks out there in space to strip-mine.

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Indeed, large scale pollution is a sign of an inefficient process and short sighted and irresponsible management. It is not an inevitable result of industrialisation.

Jon

It's far cheaper to mine here on Earth. You could explore, prove up, and develop a world class ore body in any commodity you care to mention for the cost of one shuttle launch.

Other issues: we are not running out of any metallic mineral commodity, despite unprecendented consumption. We don't know how to mine in zero gravity, this includes the entire processes from excavation through milling, smelting, and disposal of waste. We don't have the technology to economically explore asteroids, let alone economically move thousands of tonnes of material round in space, both setting up the plant on the asteroid and then shipping it back to Earth.

We have got to crawl before we can take bady steps. As far as space mining is concerned, crawling will include being able to excavate useful amounts of lunar and martian regolith for construction purposes. Then we can move on to volatile extraction and then the harder things - lunar oxygen, production of iron and tiantium and aluminium. By then we may be in a position to start thinking about mining the asteroids. Even there, the most vaulable resource is not metals, but volatiles. Volatile extraction on Phobos and Deimos will be hpow we learn to work on asteroids.

None of this is for the terrestrial economy, all is to increase the efficiency and reduce the cost of space operations. Mining asteroids for metals and exporting them to earth is economic fantasy for a long time to come.

Jon

I'd love to see what the experiments with synthesized regolith in concrete mixing came up with.

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

I agree. I would be happy with all fissionable material being placed on the moon--with conventional reactors there beaming power to Earth.

Let someone try to fly an airliner into that.

Meltdown? No biggie--its the moon.