Lunar tech startup aims to extract rare helium isotope from the Moon

US-based startup Interlune is developing a lunar soil processing system to extract helium-3, a rare isotope on Earth believed to be more abundant in the Moon’s regolith, which is essentially a blanket of dust and broken rocks on the lunar surface.

The company is working with industrial equipment manufacturer Vermeer to create what is likely to be a prototype system, which will process up to 100 tonnes of lunar regolith per hour before separating the gases and isolating helium-3.

The system is expected to excavate the top few metres of regolith, after which the material will be sorted and heated to 700 to 900°C to release the embedded gases. These are then separated using cryogenic or pressure-swing adsorption techniques to isolate helium-3.

In concept, lunar extraction of the gas is straightforward but in practice it is highly complex and costly.

“The high-rate excavation needed to harvest helium-3 from the Moon in large quantities has never been attempted before, let alone with high efficiency,” said Gary Lai, Interlune co-founder and CTO.

Government and industry have been seeking a new and scalable source of the rare isotope since the US government identified a severe shortage around 2010.

Helium-3 is used in neutron detection, cryogenics, medical imaging (such as lung MRI), and is being researched as a potential fuel for fusion energy due to its aneutronic properties. This refers to a type of fusion reaction that does not produce neutrons, which cause problems associated with damaging radiation.

A render of how the helium-3 harvesting technology may look ©Interlune

However, there are major economic and technical challenges to be overcome before the technology can be scaled. After the gas mixture is processed it must be stored in pressurised cryogenic tanks and transported back to Earth at enormous cost due to launch mass and cryogenic containment.

The isotope is also extremely scarce. Even high-grade regolith only contains about 10-20 micrograms of helium-3 per kilogramme. This means over 100 million tonnes of regolith needs to be processed each year to fuel even one large fusion power plant.

Despite this, the US Department of Energy under its Isotope Programme agreed earlier this year to procure up to three litres of helium-3 for delivery on Earth no later than April 2029.

“The inaugural purchase of lunar helium-3 from Interlune demonstrates the crucial need for a larger supply of this resource here on Earth,” said Rob Meyerson, Interlune co-founder and CEO.

To extract three litres of helium-3, Interlune will have to process enough lunar regolith to fill a large backyard swimming pool and the amount will be too large to return to Earth.

“Processing this amount of regolith requires us to demonstrate our operations at a useful scale on the Moon,” explained Meyerson. To do this, the company has outlined plans to build a pilot plant on the Moon’s surface.

In the future, it aims to supply “other lunar-derived resources” for use in space to advance further space exploration.

The company has so far raised around $18m including individual grants from the US DOE and NASA TechFlights to develop its technology and is planning several missions to the Moon later this decade.