Seattle-based Interlune says it has managed to produce 99% pure helium-3 from a standard supply of industrial-grade helium, marking a milestone for a technology that the company aims to use on the moon. The process, known as Cold Capture, could be profitably used on Earth even before Interlune begins lunar mining operations. Only 0.000137% of the world’s helium exists in the form of helium-3, as opposed to the much more common helium-4 isotope. But helium-3 is uniquely suited for use as a refrigerant for quantum computers. It can also be used in radiation detectors, medical scanners and eventually fusion reactors. Because of its rarity and utility, the price of helium-3 can range as high as $20 million per kilogram ($9 million per pound). Interlune is betting on the proposition that helium-3 is more abundant and easier to access on the moon, due to the lunar surface’s exposure to the solar wind. If Interlune’s business model works out, the company will be able to turn a profit by delivering lunar helium-3 to Earth for industrial applications. Interlune’s first objective was to show that Cold Capture could work as advertised. The process uses cryogenic distillation to separate helium-3 from ordinary helium at temperatures approaching absolute zero. “Capturing helium-3 from existing helium sounds deceptively simple,” Gary Lai, Interlune’s chief technology officer, said in a news release. “But helium-3 and ordinary helium are almost chemically identical, making them extraordinarily difficult to separate. Cold Capture exploits subtle physical differences between the two isotopes at cryogenic temperatures to recover helium-3 in a process designed to scale.” Interlune demonstrated Cold Capture at a small scale in early 2025, and received a $1.25 million small-business grant from the Department of the Air Force last November to scale up the technology for commercial production. Based on the experiments conducted