Researchers and space enthusiasts seehelium 3 as the perfect fuel source: extremely potent, nonpolluting, withvirtually no radioactive by-product. Proponents claim its the fuel ofthe 21st century. The trouble is, hardly any of it is found on Earth.But there is plenty of it on the moon.
Society is straining to keep pace withenergy demands, expected to increase eightfold by 2050 as the world populationswells toward 12 billion. The moonjust may be the answer.
“Helium 3 fusion energy may be thekey to future space exploration and settlement,” said Gerald Kulcinski,Director of the Fusion Technology Institute (FTI) at the University ofWisconsin at Madison.
Scientists estimate there are about1 million tons of helium 3 on the moon, enough to power the world for thousandsof years. The equivalent of a single space shuttle load or roughly 25 tonscould supply the entire United States’ energy needs for a year, accordingto Apollo17 astronaut and FTI researcher Harrison Schmitt.
Cash crop of the moon
When the solar wind, the rapid streamof charged particles emitted by the sun, strikes the moon, helium 3 isdeposited in the powdery soil. Over billions of years that adds up. Meteoritebombardment disperses the particles throughout the top several meters ofthe lunar surface.
“Helium 3 could be the cash crop forthe moon,” said Kulcinski, a longtime advocate and leading pioneer in thefield, who envisions the moon becoming “the Hudson Bay Store of Earth.”Today helium 3 would have a cash value of $4 billion a ton in terms ofits energy equivalent in oil, he estimates. “When the moon becomes an independentcountry, it will have something to trade.”
Fusion research began in 1951 in theUnited States under military auspices. After its declassification in 1957scientists began looking for a candidate fuel source that wouldn’t produceneutrons. Although Louie Alvarez and Robert Cornog discovered helium 3in 1939, only a few hundred pounds (kilograms) were known to exist on Earth,most the by-product of nuclear-weapon production.
Apollo astronauts found helium 3 onthe moon in 1969, but the link between the isotope and lunar resourceswas not made until 1986. “It took 15 years for us [lunar geologists andfusion pioneers] to stumble across each other,” said Schmitt, the lastastronaut to leave footprints on the moon.
For solving long-term energy needs,proponents contend helium 3 is a better choice than first generation nuclearfuels like deuterium and tritium (isotopes of hydrogen), which are nowbeing tested on a large scale worldwide in tokamak thermonuclear reactors.Such approaches, which generally use strong magnetic fields to containthe tremendously hot, electrically charged gas or plasma in which fusionoccurs, have cost billions and yielded little. The International ThermonuclearExperimental Reactor or ITER tokamak, for example, won’t produce a singlewatt of electricity for several years yet.
Increases production and safety costs
“I don’t doubt it will eventually work,”Kulcinski said. “But I have serious doubts it will ever provide an economicpower source on Earth or in space.” That’s because reactors that exploitthe fusion of deuterium and tritium release 80 percent of their energyin the form of radioactive neutrons, which exponentially increase productionand safety costs.
In contrast, helium 3 fusion wouldproduce little residual radioactivity. Helium 3, an isotope of the familiarhelium used to inflate balloons and blimps, has a nucleus with two protonsand one neutron. A nuclear reactor based on the fusion of helium 3 anddeuterium, which has a single nuclear proton and neutron, would producevery few neutrons — about 1 percent of the number generated by the deuterium-tritiumreaction. “You could safely build a helium 3 plant in the middle of a bigcity,” Kulcinski said.
Helium 3 fusion is also ideal for poweringspacecraft and interstellar travel. While offering the high performancepower of fusion — “a classic Buck Rogers propulsion system” — helium3 rockets would require less radioactive shielding, lightening the load,said Robert Frisbee, an advanced propulsion engineer at NASA’s Jet PropulsionLaboratory in Pasadena California.
Recently Kulcinski’s team reports progresstoward making helium 3 fusion possible. Inside a lab chamber, the Wisconsinresearchers have produced protons from a steady-state deuterium-helium3 plasma at a rate of 2.6 million reactions per second. That’s fast enoughto produce fusion power but not churn out electricity. “It’s proof of principle,but a long way from producing electricity or making a power source outof it,” Kulcinski said. He will present the results in Amsterdam in midJuly at the Fourth International Conference on Exploration and Utilizationof the Moon.
Size of a basketball
The chamber, which is roughly the sizeof a basketball, relies on the electrostatic focusing of ions into a densecore by using a spherical grid, explained Wisconsin colleague John Santarius,a study co-author. With some refinement, such Inertial Electrostatic Confinement(IEC) fusion systems could produce high-energy neutrons and protons usefulin industry and medicine. For example, the technology could generate short-livedPET (positron emission tomography) isotopes on site at hospitals, enablingsafe brain scans of young children and even pregnant women. Portable IECdevices could bridge the gap between today’s science-based research andthe ultimate goal of generating electricity, Santarius said.
This fall, the University of Wisconsinteam hopes to demonstrate a third-generation fusion reaction between helium3 and helium 3 particles in the lab. The reaction would be completely voidof radiation.
“Although helium 3 would be very exciting,”says Bryan Palaszewski, leader of advanced fuels at NASA Glenn ResearchCenter at Lewis Field, “first we have to go back to the moon and be capableof doing significant operations there.”
Indeed for now, the economics of extractingand transporting helium 3 from the moon are also problematic. Even if scientistssolved the physics of helium 3 fusion, “it would be economically unfeasible,”asserted Jim Benson, chairman of SpaceDev in Poway, California, which strivesto be one of the first commercial space-exploration companies. “UnlessI’m mistaken, you’d have to strip-mine large surfaces of the moon.”
While it’s true that to produce roughly70 tons of helium 3, for example, a million tons of lunar soil would needto be heated to 1,470 degrees Fahrenheit (800 degrees Celsius) to liberatethe gas, proponents say lunar strip mining is not the goal. “There’s enoughin the Mare Tranquillitatis alone to last for several hundred years,” Schmittsaid. The moon would be a stepping stone to other helium 3-rich sources,such as the atmospheres of Saturn and Uranus.
Benson agreed that finding fuel sourcesin space is the way to go. But for him, H2O and not helium 3 is the idealfuel source. His personal goal is to create gas stations in space by miningasteroids for water. The water can be electrolyzed into hydrogen or oxygenfuel or used straight as a propellant by superheating with solar arrays.”Water is more practical and believable in the short run,” he said.
But proponents believe only helium3 can pay its own way.
“Water just isn’t that valuable,” Schmittsaid. Besides the helium, a mining process would produce water and oxygenas by-products, he says.