The US has flown one nuclear reactor in space—SNAP-10A in 1965. More than sixty years later, Antares would like to make it two.
The nuclear microreactor startup announced today that it won a $161M DoD contract to advance nuclear power for space—which Antares says is the largest DoD space nuclear award to date.
Antares and its Mark-0 microreactor made history in June, becoming the first private company to bring an advanced reactor to criticality—when a nuclear fission chain reaction becomes self-sustaining—under the Department of Energy’s Reactor Pilot Program.
Fresh off a $470M Series C in July, Antares is looking to run its electricity-producing Mark-1 reactor for more than six months in 2027.
“We’ve been building toward this moment since the day we founded Antares, before there was a program or a policy or a check,” Antares cofounder and CEO Jordan Bramble told Payload via email.
Superiority complex: The Strategic Breakthrough award comes from the Office of the Assistant Secretary of the Air Force for Space Acquisition and Integration (SAF/SQ), which runs Space Force acquisition.
The program tasks Antares with:
- Performing a ground demonstration of the R1-S, a version of its flagship heat-pipe microreactor;
- Integrating with a spacecraft for flight certification prior to launch;
- Powering an operational ground-to-space asset with Mark-1.
The award advances the Trump administration’s push to launch nuclear reactors in space as early as 2028 and on the lunar surface by 2030, under the executive order on “Ensuring American Space Superiority.”
Space is hard: Nuclear reactors are difficult enough on Earth, but the engineering challenges hit critical mass once those reactors leave the atmosphere.
For the Space Force, the appeal is less about the reactor than what it unlocks. Steady, always-on power lets spacecraft maneuver without regret rather than rationing every burn, and it feeds the heavy compute, directed energy, and electromagnetic warfare systems that solar panels cannot keep lit.
Antares has never been shy about its scope. “Our tagline, from the company’s earliest days, has been ‘abundant energy from Earth to the asteroid belt,’” Bramble said. “Every decision we made, from our heat-pipe architecture to manufacturability, was deliberate to ensure our technology would be practical both on Earth and in space.”
Chain reaction: The award follows a series of recent wins for Antares across the DoD enterprise.
- In August, the Army picked Antares to deploy a microreactor at Fort Bragg, one of five companies under Project Janus.
- A week earlier, SpaceWERX named it one of 11 STRATFI awardees, a program meant to bridge the “valley of death.”
- And in April, the Air Force tapped Antares for a prototype at Joint Base San Antonio under DIU’s Advanced Nuclear Power for Installations initiative.
“The [space nuclear] market is not mature, but this is about a renewed focus on American space superiority,” Bramble said. “It will take American ingenuity and American hardware to get there. I couldn’t be more proud that it’s the Antares team carrying that.”
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