Antares Nuclear
Category: AI in Defense / Aerospace
Antares Nuclear develops factory-produced fission microreactors (R1) for defense, space, and critical infrastructure applications, using TRISO fuel and sodium heat-pipe cooling. Antares Nuclear was founded in 2023. The company is led by Jordan Bramble. Based in Redondo Beach / Torrance, California, United States. Team size: 101-500. Total funding raised: $604M. Latest round: Series C. Key investors include Paradigm, Caffeinated Capital, Shine Capital, Alt Capital, Point72 Ventures, Industrious Ventures, Balerion Space Ventures, 53 Stations, FiftyThree Stations.
- Founded
- 2023
- Headquarters
- Redondo Beach / Torrance, California, United States
- Team size
- 101-500
- Total funding
- $604M
Value proposition
Factory-produced, transportable fission microreactors delivering 100 kW - 1 MW of resilient, carbon-free power for 6+ years without refueling, purpose-designed for defense-critical assets and remote/strategic locations.
Products and solutions
R1 Microreactor (100 kWe - 1 MWe, sodium heat-pipe cooled, TRISO fuel, nitrogen Brayton cycle power conversion), Mark-0 demonstration reactor (achieved criticality June 2026 at Idaho National Laboratory), Vertically integrated capabilities: heat pipes & thermal management, control systems, graphite machining, power management & distribution
Unique value
First privately developed non-light-water reactor to achieve criticality in the U.S. in over 40 years (Mark-0, June 2026); vertically integrated manufacturing (322,000 sq-ft Antares Prime facility); sodium heat-pipe cooling with passive safety; one of three finalists in Pentagon's ANPI program for Air Force base deployments.
Target customer
U.S. Department of Defense (military bases, Air Force, Space Force); NASA (space applications); U.S. Department of Energy; critical infrastructure operators
Industries served
Defense & Military, Space, Critical Infrastructure, Government/Public Sector
Technology advantage
Sodium heat-pipe reactor cooling (passive, no pumps or water required); TRISO fuel in prismatic graphite core; nitrogen Brayton cycle power conversion (<300 psi, low maintenance); autonomous control systems with hardware-in-the-loop digital twins; vertically integrated supply chain (322,000 sq-ft factory); HALEU fuel allocation from DOE; first approved Nuclear Safety Design Agreement (NSDA) for a microreactor.
How they differentiate
Antares differentiates through its sodium heat-pipe cooled microreactor design (no water cooling, enabling passive safety and dry cooling), vertically integrated in-house manufacturing (graphite machining, heat pipes, control systems), and a dual-use strategy targeting both defense (price-insensitive military customer) and space (NASA) applications. The company achieved the first criticality of a privately developed non-light-water reactor in the U.S. in over 40 years.
Main competitors
Radiant Industries (Kaleidos microreactor), Last Energy (microreactor SMR), X-energy (Xe-100 SMR), Oklo (Aurora microreactor), Aalo Atomics
Key partnerships
Idaho National Laboratory (INL) - $40M strategic partnership, reactor testing at DOME facility, Urenco - multi-year HALEU supply agreement (world's first commercial), Savannah River National Laboratory (CRADA), Oak Ridge National Laboratory (DOE GAIN voucher), Sandia National Laboratories, U.S. Department of Energy Reactor Pilot Program, Defense Innovation Unit (DIU) - ANPI program, NASA, U.S. Air Force, Space Force
Notable customers
U.S. Department of Defense (Air Force, Space Force), Defense Innovation Unit (DIU), NASA, Joint Base San Antonio (ANPI program), U.S. Department of Energy
Major milestones
2023-10: $8M Seed round raised, 2024-03: First sodium heat pipe demonstrated, 2024-10: $30M Series A raised, 2025-02: Antares Prime factory opened (322,000 sq-ft), 2025-08: Selected for DOE Reactor Pilot Program, 2025-10: First approved NSDA for a microreactor, 2025-12: $96M Series B raised, 2026-04: Selected for ANPI program (Joint Base San Antonio), 2026-05: Multi-year HALEU supply agreement with Urenco, 2026-06: Mark-0 achieves criticality at INL (first private non-LWR in 40+ years), 2026-07: $470M Series C raised
Market positioning
Antares is positioned as a leading U.S. microreactor developer focused on defense and space applications, having achieved the first privately developed non-light-water reactor criticality in 40+ years. It is one of three finalists in the Pentagon's ANPI program and has secured contracts with the U.S. Air Force, Space Force, DIU, and NASA. The company competes in the rapidly growing advanced nuclear market fueled by AI data center power demand.
Geographic focus
United States (primary: U.S. military bases, DOE sites, NASA); potential global expansion for allied defense partners
Patents and IP
Not publicly disclosed beyond proprietary heat-pipe and reactor design details. The company holds an approved Nuclear Safety Design Agreement (NSDA) from DOE and has NRC pre-application engagement (Docket 99902149).
About Jordan Bramble
Ex-White House Office of Management and Budget (directed strategic advanced energy portfolios); Ex-Northrop Grumman (System Engineer); Astrophysics Research Assistant at George Mason University. Holds degrees in Systems Engineering, Physics, and Statistics from George Mason University and Georgetown University.
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Official website: https://antaresindustries.com/