Antares Nuclear Inc., a Torrance, California startup founded in 2023, has received a $161 million Strategic Breakthrough award from the Office of the Assistant Secretary of the Air Force for Space Acquisition and Integration to advance its space nuclear reactor programme. Antares announced its selection on September 11 and said the work would support the development and certification of a reactor for use with a spacecraft.
The award will fund ground demonstrations of Antares’ R1-S reactor design, which is the space version of the company’s terrestrial heat-pipe microreactor. After the ground work, Antares plans to integrate the R1-S with a spacecraft for flight certification. The company has not disclosed a target launch date for the reactor, or identified the spacecraft or mission it would support.
Antares described the contract as the largest current Department of War award in space nuclear power. The award arrives as the US government pursues plans for nuclear reactors in orbit and on the lunar surface, with policy placing particular weight on space superiority.
Executive Order 14369, titled ‘Ensuring American Space Superiority’, forms part of that policy setting. The National Initiative for American Space Nuclear Power, under NSTM-3, calls for reactors in orbit as early as 2028 and on the lunar surface by 2030. Those are national targets, rather than a launch schedule announced by Antares for the R1-S.
The company will also operate its Mark-1 reactor, which produces electricity, at a ground-to-space test site. Mark-1 testing is scheduled for 2027, when the reactor is scheduled to run for more than six months. It will be paired with a nitrogen closed Brayton cycle power conversion system. Antares has not disclosed the operational ground-to-space asset that Mark-1 will power, or how the $161 million will be divided between the R1-S demonstration and Mark-1 testing.
Antares has recently cleared an earlier technical milestone. On June 4, its Mark-0 microreactor reached initial criticality at Idaho National Laboratory. The company became the first private company to bring an advanced reactor to criticality through the Department of Energy’s Reactor Pilot Program.
Jordan Bramble, Antares’ chief executive and co-founder, leads a company backed by over $600 million in funding. Its work for the Air Force follows another military selection in August, when Antares was chosen for the Army’s Project Janus. Under that programme, it is one of five firms selected to produce up to 20 microreactors at military bases through a contract worth up to $2.2 billion, with first delivery targeted by 2028.
The two programmes address different settings, one terrestrial and the other intended to prepare a reactor for spaceflight. Together, they place Antares among the companies seeking to turn small nuclear reactor designs into operational military power systems within the government’s stated timelines.
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