Antares

Antares builds factory-produced nuclear fission microreactors for defence and space customers. Its R1 unit generates 100kWe to 1MWe for six or more years without refuelling, using TRISO fuel, sodium heat pipes and a nitrogen Brayton power conversion cycle, with integrated shielding so it can be transported and sited at military installations, in space and undersea. Founded in 2023 by Jordan Bramble and Julia DeWahl and headquartered in Torrance, California, with sites in Idaho Falls and Aiken, South Carolina, it holds contracts with the US Air Force, Space Force, NASA and the Defense Innovation Unit; its Mark-0 reactor reached criticality at Idaho National Laboratory in June 2026, the first privately developed non-light-water reactor to go critical in the US in over 40 years.