Antares Nuclear has been awarded a $161m Strategic Breakthrough contract by the Office of the Assistant Secretary of the Air Force for Space Acquisition and Integration to advance nuclear fission power for space missions. This agreement marks the largest current Department of War (DOW) award dedicated to space nuclear power.
The programme aims to address a 60-year orbital power gap – the US has not operated a nuclear reactor in space since the SNAP-10A mission in 1965. Under this contract, the initiative will progress through a series of milestones. Antares will conduct a comprehensive nuclear ground demonstration of its R1-S (R1-Space) microreactor, which is adapted from its heat-pipe architecture. The company will also power an operational ground-to-space asset with Mark-1, its electricity-producing reactor, scheduled for testing in 2027.
Following successful ground tests, the system will be integrated with a spacecraft for flight certification ahead of a planned orbital launch. The Space Force intends to use continuous, sun-independent nuclear power to remove manoeuvrability constraints on spacecraft. This energy source will support heavier data computation loads, directed energy systems, and electromagnetic warfare capabilities.
The project directly supports national directives, including President Trump’s December 2025 Executive Order 14369, Ensuring American Space Superiority, and the National Initiative for American Space Nuclear Power established by National Security and Technology Memorandum-3 (NSTM-3), which direct the launch of nuclear reactors in space as early as 2028 and landing on the lunar surface by 2030.
“Space has been core to the Antares thesis since the company was founded,” said Jordan Bramble, CEO and co-founder of Antares. “This partnership with the Space Force turns that long-held vision into a codified space mission. Fission will unlock strategic capabilities that are impossible today.”
According to Antares, nuclear power removes propulsion constraints for the Space Force, allowing spacecraft to manoeuvre without regret and carry out dynamic operations that were once impossible. “Most importantly, it brings high, always-on power to support heavier compute loads, directed energy systems, and the future of electromagnetic warfare.”
In June, the Antares Mark-0 microreactor was the first reactor to achieved zero-power criticality at Idaho National Laboratory under Department of Energy (DOE) authorisation through the DOE Reactor Pilot Program. The company’s Mark-1 reactor is scheduled to operate for more than six months in 2027, integrated with its nitrogen closed Brayton cycle power conversion system. Antares, founded in 2023 and backed by over $600m in funding, operates facilities in Torrance, California; Idaho Falls, Idaho; and Aiken, South Carolina.
Just over a week after signing the space contact, Antares and Centrus Energy signed a definitive multi-year contract for Centrus to supply Antares with high-assay low-enriched uranium (HALEU), with deliveries starting before the end of the decade. It ensures a reliable, domestic source of HALEU to support Antares advanced reactor projects, including for space and national security missions. The new contract includes prepayments from Antares to support the expanded HALEU capacity.
“This contract is another sign that demand for HALEU is real and it is accelerating, and Centrus is in prime position to meet this need,” said Centrus President and CEO Amir Vexler. “Binding orders from Antares and others are supporting our expansion to commercial-scale production – an expansion that is now well underway. We look forward to supporting Antares’ continued growth and success.”
Antares CEO Bramble noted: “Fuel supply is one of the practical questions every advanced reactor developer has to answer. This contract gives Antares a reliable, US-origin source of HALEU for the reactors we’re deploying for a wide variety of defence and space customers.” As well as the space contract, Antares was recently selected for the US Army’s Janus Program at Fort Bragg, North Carolina and the Air Force’s Advanced Nuclear Power for Installations program at Joint Base San Antonio, Texas.
Centrus is pioneering US HALEU production at its American Centrifuge Plant in Piketon, Ohio, the only licensed HALEU production facility in the US. Last year, Centrus launched a multi-billion-dollar expansion including large-scale production of HALEU as well as Low-Enriched Uranium (LEU). Because Centrus’s enrichment technology and manufacturing supply chain are US-origin, the arrangement can provide Antares with fuel that could be used for a variety of national security applications. Centrus’s AC100 centrifuge design is the only deployment-ready enrichment technology capable of “unobligated” enrichment, meaning that it can be used for national security missions.
