Antares raises $96 million for nuclear reactors on Earth and in space

WASHINGTON — Nuclear power startup Antares announced a $96 million Series B round Dec. 2 to fund work on developing small nuclear reactors, including for space applications.

The company said the Series B round included $71 million in equity led by Shine Capital, with participation from Alt Capital, Caffeinated, FiftyThree Stations, Industrious and other investors. The company also secured $25 million in debt.

The 60-person startup, with operations in California, Idaho and South Carolina, is working on scalable nuclear reactors that could be used for terrestrial and space applications. The new funding will go toward building a California factory capable of producing 10 reactors a year, as well as equipment and uranium fuel procurement.

“We’re months away from our first reactor demonstration, which will validate our control systems and neutronics models, develop our testing facility and fabricate our fuel ahead of our upcoming full-scale electricity-producing prototype in 2027,” Jordan Bramble, chief executive of Antares, said in a statement.

That reactor demonstration, called Mark-0, is set to begin testing next year at the Department of Energy’s Idaho National Laboratory. It will support development of the prototype reactor, Mark-1, planned for 2027.

Antares has also been working with NASA on aspects of its reactor technology. The company said it tested an electrically heated prototype, designed for thermal and mechanical testing, over the summer at Marshall Space Flight Center.

The company sees opportunities with both the military and NASA for its planned microreactors, compact and easily transportable units designed to provide power in remote environments.

That includes space. Antares said it is interested in NASA’s Fission Surface Power (FSP) program, which aims to develop a reactor capable of producing at least 100 kilowatts on the lunar surface.

“This program’s requirements align with our manufacturing core competencies and design,” Bramble said of FSP. “We believe nuclear power is critical to enabling a space-based industrial economy.”

NASA announced new plans in August for developing nuclear reactors on the moon. A directive signed by Acting Administrator Sean Duffy called for public-private partnerships to support development of a reactor ready for lunar deployment by 2030. The directive came weeks after a report by Idaho National Laboratory urging rapid development of nuclear power and propulsion technologies after decades of limited progress.

NASA issued a draft solicitation in late August, known as an Announcement for Partnership Proposals, for the program. It called for using Space Act Agreements to support reactor development. Companies would own the reactors they develop and sell power to NASA or other customers through services contracts.

NASA had planned to release a final version of the solicitation in early October, but the timeline was delayed by the six-week government shutdown that began Oct. 1. In a Nov. 19 procurement notice, NASA said it would issue a second draft Dec. 5, with the final version now expected in early 2026.