Mining the Moon for Fusion Energy

Don't Look to the Moon to Meet U.S. Energy Needs Just Yet


c. 2004 Newhouse News Service

Mining the moon might supply the Earth with clean fusion energy someday, but not any time soon.

The top few feet of the moon's surface, called the lunar regolith, contains about 1 million metric tons of helium-3, a near-perfect fuel for nuclear fusion. Rare on Earth, the gas is an isotope, or variant, of the same helium that floats party balloons.

Just "one pound of helium-3 could produce anywhere from one to 10 million times the electricity of a ton of coal," said Gerald L. Kulcinski, director of the Fusion Technology Institute at University of Wisconsin-Madison, which has been researching helium-3 fusion since 1986.

A mere 30 metric tons, roughly one space shuttle load, could fill the United States' electricity needs for a year, said Harrison H. Schmitt, a former Apollo astronaut and chairman of Interlune-InterMars Initiative, a company that promotes commercializing moon resources. (A U.S. ton equals 2,000 pounds; a metric ton equals 2,204.62 pounds.)

But while the gas might someday prove a valuable power source, "nobody's running out to the grocery store for helium-3 to fuel their reactors," said Glen A. Wurden, a fusion researcher at Los Alamos National Laboratory in Los Alamos, N.M.

Scientists haven't yet figured out how to generate fusion power with materials much easier to use -- and more readily available on Earth -- than helium-3. And even once astronauts are on the moon, extracting the gas from rocks could prove a task equal to Hercules shoveling out the Augean stables.

Fusion, the process that fuels the sun, is the holy grail of nuclear energy. It smashes together atoms to release energy, rather than splitting them apart as modern fission reactors do. Fusion has the potential to produce power that releases no greenhouse gases and creates little or no radioactive waste. But in more than 50 years' research, scientists have been unable to create a fusion reaction that puts out more energy than goes into starting or sustaining it.

Most of today's fusion research uses the hydrogen isotopes deuterium and tritium, which fuse at relatively low temperatures, about 100 million degrees, Wurden said. But deuterium and tritium mixtures release about 80 percent of their energy in the form of fast neutrons, which produce radioactive waste.

A helium-3 and deuterium mix gives off much fewer fast neutrons, but requires about four times the temperature to react. A pure helium-3 reaction, on the other hand, would produce zero radioactive waste at the cost of even higher temperatures.

And heat's not the only problem. Helium-3 atoms are about 10 times harder to fuse together than tritium and deuterium and so require more advanced containment systems than we know how to build today, said Wurden, who is the Los Alamos program manager for the U.S. Department of Energy's Office of Fusion Energy Sciences.

"Nobody questions that helium-3 is a great fuel," Wurden said. "The problems are it's on the moon and we haven't even built a reactor good enough for a simple deuterium-tritium fuel mix."

Scientists looking beyond today's fuels are more likely to concentrate on a mixture of hydrogen and boron-11 than pure helium-3, Wurden said. The mix requires over 1 billion degrees to fuse, but it could generate electricity directly with no radioactive waste, and it's readily available on Earth today, he said.

But Kulcinski countered that pure helium-3 reactions are easier to create than hydrogen and boron-11. And even though the world's supply of helium-3 can be counted in hundreds of kilograms, President Bush's plans for a moon base mean there will be a supply of the isotope sometime in the future.

Even if the physics weren't so difficult, mining helium-3 would present challenges.

While the isotope is relatively abundant on the moon, it still occurs at only 50 parts per million, said Alan Binder, director of the Lunar Research Institute in Tucson, Ariz., which advocates commercializing the moon's resources. That means shoveling 20,000 metric tons of regolith into 700-degree ovens to boil off one metric ton of the precious isotope, which must be sorted out from regular helium and other naturally occurring elements, like hydrogen and oxygen. Of course, there's also the expense of transporting it back to Earth.

But Binder doesn't expect miners to fly to the moon for the express purpose of bringing back the isotope. Instead, he said, helium-3 would be harvested as a byproduct of building and maintaining a lunar settlement.

Schmitt predicted the gas could be returned to Earth for under $1 billion a metric ton. Kulcinski adds that, if it sold for $4 billion a metric ton, helium-3 would still be a good energy value: "That's the equivalent of paying $28 a barrel for oil."

But extracting any sort of resource from the moon raises a raft of legal questions, said Joanne Irene Gabrynowicz, director of the National Remote Sensing and Space Law Center at the University of Mississippi School of Law. The Outer Space Treaty, to which 100 nations including the United States are signatories, bars any nation from owning the moon or other space bodies, forbids militarization and requires them to share the benefits of space, Gabrynowicz said.

"On the issue of resource ownership, the treaty regime is silent," she said. "The Outer Space Treaty neither prohibits nor allows the appropriation of resources."

Fortunately, there is time to sort these issues out, at least for helium-3. Fusion energy probably won't be ready for prime time when astronauts once again reach the moon, experts agreed. Kulcinski predicts fusion power in 30 to 40 years. Wurden is more pessimistic: "Frankly, fusion reactors are still a 50-year thing."