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Once Again: Helium-3 From The Moon Is Not Going to Solve Our Energy Problems

Tuesday, May 10, 2011 23:00
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I have to admit that I’m all for space exploration, but this is not why…

Via Popular Science:

Former Apollo Astronaut and Senator Says Mining Helium on the Moon Could Solve The Global Energy Crisis

Former astronaut, Apollo moonwalker, geologist and former Senator Harrison Schmitt has a modest plan to solve the world’s energy problems. All we need is $15 billion over 15 years and some fusion reactors that have yet to be invented. And we’ll need a moon base.

Schmitt’s idea isn’t novel–he thinks the U.S. should go back to the moon, this time to mine the surface for helium-3, an isotope of helium that is rare on earth but relatively bountiful on the moon. The Russians have been talking about mining helium-3 from the moon for years, but they’ve never put forth a viable plan. Schmitt thinks his, all things considered, is pretty realistic.

So how does Schmitt’s plan break down? We’ll need $5 billion for a helium-3 fusion demonstration plant, because as of right now no such thing exists. We’ll also need to invest $5 billion more in a heavy-lift rocket capable of launching regular moon missions, something akin to the Apollo-era Saturn V.

A moon base for mining the stuff would cost another $2.5 billion, and though Schmitt didn’t really specify in his recent presentation to a petroleum conference, the other $2.5 billion could easily be chalked up to operating costs in an endeavor of this magnitude.

But it could pay for itself while developing critical spaceflight technologies and enabling a mission to Mars. Schmitt says a two-square-kilometer swath of lunar surface mined to a depth of roughly 10 feet would yield about 220 pounds of helium-3. That’s enough to run a 1,000-megawatt reactor for a year, or $140 million in energy based on today’s coal prices. Scale that up to several reactors, and you’ve got a moneymaking operation.

Why go to all this trouble? Helium-3 is abundant on the moon and produces little to no radioactive waste that must be cleaned up and stored. The reaction necessary would burn at a much hotter temperature than other fusion reactions, but the chance of environmental disaster via radioactive spill is virtually nil. Plus we would establish a permanent presence on the moon.

Throw in another $5 billion, and we might even be able to populate said moon base with a clone work force and some soothing, Kevin Spacey-esque AI.

Did anyone miss the part about the fusion reactors that HAVE YET TO BE INVENTED? Aside from that, a number of the contentions made are just plain wrong: Helium-3 fusion does not produce zero radioactive waste, it’s not that abundant on the moon and you would not just need a Saturn-V sized rocket, but thousands of them.

Now five reasons why this whole idea is stupid

#1.  We have no way to use helium-3 fusion or fusion of any elements to produce usable energy.

Let me repeat this because it is by far the most important deal breaker on this whole issue:  nuclear fusion for the purpose of energy generation does not exist.   The only way we can produce fusion energy that is greater than the energy necessary to initiate and contain the fusion is with an H-bomb.  Fusion can also be produced in the laboratory, but it always uses more energy than it produces.   Also, producing more than a relatively small amount of nuclear fusion requires extremely complex and costly equipment.

Since fusion reactions do produce energy, it is possible, at least in theory, that fusion could be used as an energy source IF the technical challenges could be overcome.   To this end, a great deal of research is being conducted just as it has been for decades.

Will fusion power ever become a reality?   Maybe.   Then again, maybe not.   It’s possible that tomorrow a researcher will stumble across a novel way of producing nuclear fusion cheaply and simply while generating huge amounts of energy.   I wouldn’t bank on it though.

There are several methods of producing fusion which are being investigated as potential energy sources.  The one that has received the most effort is magnetic confinement fusion using the tokomak design.   Some tokomaks have approached “break even” energy balances for short periods of time.  An ambitious project is currently under way known as the International Thermonuclear Experimental Reactor. It is expected to begin operation in 2018 with the ambitious goal of producing more energy than is consumer for periods of several minutes.

Of course, a project like ITER is not going to represent any kind of major power source. In order for that to happen, fusion power systems will need to operate reliably for extended periods of time. Not only that, but they will need to be economical enough to be built by the hundreds or thousands. If the current path of fusion research is followed, we have no chance of seeing effective fusion power generation for at least many decades, if ever.

#2.  It offers few, if any, advantages over other potential fuels

Most fusion research has focused on deuterium and/or tritium (heavy isotopes of hydrogen) as fuel for generating fusion.   The lowest energy (and thus easiest) fusion reaction to produce uses deuterium fusing with tritium.  Deuterium on deuterium fusion is another option, which requires slightly more energy and higher temperatures.  Other research has considered the use of boron as a fusion fuel.

Deuterium is found in abundance in all water on earth.   Tritium is not found in nature but can be produced by the neutron bombardment of lithium.   Boron is also easily obtained.

The only advantage of using helium-3 as fuel (if you can call it that), rather than deuterium and tritium is that it does not produce neutrons when it is used in combination with deuterium.   In practice any fusion reactor powered by helium-3 and deuterium will produce some neutrons because deuterium atoms will also fuse with other deuterium atoms.  So to be more accurate, a helium-3 fusion reactor would produce less neutron radiation than one fueled by deuterium alone or deuterium and tritium.

The reason that this is sometimes considered to be an advantage is that neutron irradiation tends to leave materials radioactive and degrades most materials that would be used to construct a reactor.  Consequently, the housing of a fusion reactor would have to be replaced periodically after a certain number of years.  The old housing would be slightly radioactive and considered low-level or medium-level waste.   For those who consider all radioactive material evil this is a big problem.

However, the lack of neutron production can also be a disadvantage.   The neutrons produced by a fusion reactor could be used to generate more fuel in the form of tritium by surrounding the fusion reactor with lithium.  They also provide a way of harvesting energy from the reaction.

So a helium-3 based reactor would generate a bit less low-level waste and might need to have the housing replaced somewhat less frequently but would also not be capable of breeding more fuel.

Oh, and did I mention this is all speculation since none of these exist anyway?

#4.  Getting helium-3 from the moon is absurdly difficult

Getting to the moon is difficult.  To do so you need a big rocket and generally, you can only use that rocket once.   Because of this, any craft that goes to the moon will necessarily cost hundreds of millions of dollars to send there.  Getting something back from the moon is even harder, because it requires that a spacecraft be sent to the moon with the capability of launching itself back into space and returning to earth.   That means the spacecraft is going to have to be fairly large and heavy and thus necessitate an even larger rocket.

The Apollo Program used the Saturn-V to launch a manned capsule to the moon.   This is the largest rocket ever built and each one was only good for sending a single mission and a single lander to the moons surface.  Each Apollo Lunar Module could only carry a maximum payload of a few hundred kilograms.   Perhaps if the craft were unmanned and thus did not need to have life support systems or a crew on board, more could be brought back.   None the less, it would still require a massive expenditure and enormous rocket power to get even a ton of material back from the moon.

But there’s another problem.  Helium-3 is not just sitting in a compressed gas tank on the moon, waiting to be taken back.   It’s embedded in the rocks and soil on the surface of the moon.  The actual amount of helium-3 in a given quality of rock is miniscule, so bringing the rock back to earth to process out the He-3 is not an option.   Instead, huge volumes of rock and soil would need to be collected on the moon and brought to some kind of moon-based extraction facility.   This would be an enormous mining operation, requiring many robotic excavators and movers and a large system to extract the helium-3.  Not only that, but it would need to be powered somehow, requiring its own nuclear reactors or massive solar power systems.  Presumably each piece of equipment would require its own massive rocket to reach the moon.

Once the moon rock is collected, it would have to be pulverized and heated to outgas the helium from the rock.   Unfortunately, doing this will not result in only helium being collected.  Rather the moon rock will produce a mixture of nitrogen, oxygen, water vapor and other gases from which the helium must be chemically separated.   This would not be a huge difficulty, since helium is an inert gas, but it is being done on the moon, so all the equipment, once again, has to be launched on massive rockets.

But there’s yet another huge problem.  The helium which is extracted from lunar material contains at least 30 times more helium-4 (regular helium) than it does helium-3.  Helium-4 is nowhere near valuable enough to make it worth going to the moon to get.   This leaves two choices:  Either bring back the extracted helium and accept the fact that more than 95% of the payload is going to be wasted on helium-4 or separate the helium-3 from the helium-4 on the moon.

Isotopic separation is one of the most complex and energy intensive industrial processes in existence.  It requires massive cascades of centrifuges or gaseous diffusion membranes where gas is pumped at high pressure and isotopic concentrations are increased slightly in a process that must be repeated hundreds or thousands of times.   The mass difference between helium-3 and helium-4 and the fact that it’s already a gas would make the process slightly simpler than enriching something like uranium, but it would still require that a huge and complex operation be mounted on the moon! Yes, we’re talking about an enormous industrial facility, typically requiring at least hundreds of workers, hundreds of tons of specialized equipment and many megawatts of power on the moon.

#5 You don’t actually have to go to the moon to get helium-3

Assuming we ever develop a viable fusion reactor (which we may never do, but then again, we might in the distant future) and if we decide to run that reactor on helium-3, then we don’t actually have to build an enormous mining/extraction/enrichment establishment on the moon.   There is another way to get helium-3, and it’s where all the helium-3 used for experimental fusion, cryonics and other processes come from.

Helium-3 is the decay product of tritium.  Tritium is relatively easy to produce by the neutron bombardment of lithium targets either in a nuclear fission reactor, or, if ever fusion power reactors became available, in such a fusion reactor.  Tritium decays with a half-life of 12.3 years, so every kilogram of tritium synthesized will produce a half a kilogram of helium-3 in about 12 years.   Most of the helium-3 currently available was recovered from the tritium capsules in nuclear weapons.   As long as there is at least a few years leadtime, simply upping the production of tritium will allow for helium-3 to be collected.

It has been pointed out that producing helium-3 this way would require significantly greater tritium production than has been realized before.  Even during the height of the Cold War, the US and Soviet Union only produced a couple of kilograms a year of tritium for the purposes of nuclear weapon boosting.   If tritium-derived helium-3 were to power society, it many tons would need to be produced each year.

Still, compared to building an isotope-enriching facility on the moon, it sure seems a lot easier.

Read more at Depleted Cranium


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