Fusion project proposes mining helium-3 on the moon
An exhibit called “Fusion fuel from the moon” won first prize in the "group, graduate" category at the 2015 Engineering Expo, a large-scale public outreach event held every other year on the UW-Madison engineering campus. The group won $800 for its project, which centers around a device that could potentially extract helium-3 from the moon’s surface for sustainable energy use on earth.
The exhibit itself included a simulation on a monitor that allowed Expo visitors to search a 3D projection of the moon for potential sources of helium. Another 3D simulation gave them the opportunity to drive a robotic miner over the lunar surface.
But the center of the students' research and Expo exhibit was a cross-sectional display of a Helium-3 miner’s processing chamber. Though novel to many visitors of Expo, it has long been a work in progress for engineering physics graduate student Aaron Olson, who created the exhibit along with Abe Megahed and undergraduate students Alex Strange and Tashi Atruktsang. Megahed is a computer scientist in the Morgridge Institute for Research who helped develop the 3D simulations for the project.
Scientists have known for some time that if they use Helium-3 in a fusion reactor, they can obtain a nuclear reaction that does not produce radioactivity. Although Helium-3 is very rare on earth, it is not an uncommon commodity on the moon.
The helium that exists on the moon comes from the sun, which is continuously emitting charged particles, otherwise called solar wind. Earth doesn’t absorb these particles, because its magnetic field diverts them. But the moon, which doesn’t have a magnetic field or an atmosphere to absorb the incoming ions, takes Helium-3 and other particles into its soil.
“500 million tons of Helium-3 have hit the lunar surface, but only about a million tons have actually been retained,” Olson says. “So it’s that million tons that we’re looking to actually go and get.”
The actual process of Helium-3 extraction is complicated and thorough. Soil is drawn from the moon’s surface, and that soil, also referred to as regolith, is filtered through a heat pipe heat exchanger. This exchanger heats the material to 700 degrees Celsius using power from concentrated solar energy so that the desired solar wind gases are extracted from the batch of soil. The leftover soil contains thermal energy from this heating process. The device transfers this energy to the heating of the next batch of lunar material. In this way, the device self-propagates its own energy.
“It’s 85 percent energy-recovery-efficient,” Olson says. “Instead of using 82 megawatts of power, you can get away with using 12.3 megawatts of power, because it reuses the waste energy.”
Olson and his research group are now looking to actually build a prototype of this processing chamber, a large part of which is centered around the heat pipe heat exchanger. The students currently are designing a small-scale heating system that will eventually be constructed. Their project is called Helium Extraction and Acquisition Testbed (HEAT).
In order to test their configuration, they must first have testable material. This is where ion implantation comes in.
The group has obtained a material called JSC-1A from NASA, which is very similar to moon soil. But in order to test the processing chamber, this material must actually contain Helium-3 The group is using a controlled chamber with a glow discharge to implant Helium-4 ions (which have similar diffusion properties as Helium-3) into the JSC-1A material. After they obtain this result, they will be able to test their prototype heat pipe heat exchanger.
Olson anticipates that by the 2020s or 2030s, the space technology may exist that will allow the fusion and space communities to actually send a miner to the moon and test this technology. At this point, it’s just about technology development.
“They could go back and look at the work we’ve done here as a backdrop of how to design certain components,” Olson says.
According to Olson, who is writing his PhD thesis on this helium mining research, extracting and obtaining Helium-3 could be a huge step in renewable energy; 66 kilograms of Helium-3 provides the energy to power a 1-gigawatt electric power plant for a year, without creating radioactivity.
“There’s going to be a point in time when we’re not going to be able to use fossil fuels at the same rate we’re currently using them,” he says. “It’s going to be renewable energy and nuclear energy that are going to have to step up and be able to supply energy for the entire world.”
Not only did the group’s Expo exhibit win first prize, but it may just represent a great leap forward in how we look at and approach renewable energy in the 21st century.