Antares NuclearIn Development
Space variant of the R1 heat-pipe microreactor. Under a $161M Space Force Strategic Breakthrough award, Antares will run a nuclear ground demonstration of the R1-S, integrate it with a spacecraft for flight certification, and use Mark-1 to power an operational ground-to-space asset during 2027 testing.
Latest update Sep 18, 2026
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Award announced September 11, 2026. Ground demonstration and spacecraft integration are funded; no flight date has been published. The award is described by Antares as the largest current Department of War award in space nuclear power.
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Announced next steps from Antares Nuclear that mention R1-S.
2027-2028
Under the $161M Space Force Strategic Breakthrough award, perform a nuclear ground demonstration of the R1-S and integrate with a spacecraft for flight certification. Antares will also power an operational ground-to-space asset with Mark-1 during 2027 testing. No public flight date.
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Antares' commercial factory-built microreactor: a TRISO-fueled prismatic graphite core with graphite and boron carbide control drums, passive sodium heat pipes, a fin-and-tube primary heat exchanger, and a recuperated nitrogen closed Brayton cycle at under 300 psi. Packaged with integrated shielding and a transport cradle for defense-critical assets, rated at 100 kWe to 1 MWe for 6+ years without refueling and without a grid connection.
A full-scale, zero-power demonstration of the R1 core at Idaho National Laboratory's RACE facility, built under DOE's Reactor Pilot Program. It has no power conversion or heat-removal loop; the test validated reactor physics, control-drum behavior, and the DOE authorization pathway using BWXT-fabricated HALEU TRISO.
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NuScale Power
Full-scale SMR power plant with 12 modules generating up to 924 MWe of carbon-free electricity.
NuScale Power
Self-contained 77 MWe pressurized water reactor module with integrated steam generators.
NuScale Power
Mid-size SMR plant configuration with 6 modules producing up to 462 MWe.
Oklo
Oklo's fast-fission powerhouse product line is designed for build-own-operate deployment, targeting customers that want firm clean power in a smaller footprint than traditional large reactors.