Antares Wins $161M Space Force Nuclear Reactor Contract

Antares, a nuclear microreactor startup, has won a $161 million contract from the Department of Defense to advance nuclear power for space applications. The company states this is the largest current DoD space nuclear award.

The Strategic Breakthrough award comes from the Office of the Assistant Secretary of the Air Force for Space Acquisition and Integration, which runs Space Force acquisition. The program tasks Antares with performing a ground demonstration of its R1-S reactor, integrating the technology with a spacecraft for flight certification, and ultimately powering an operational ground-to-space asset with its Mark-1 reactor.

The Path to Criticality and Flight

Antares and its Mark-0 microreactor made history in June by becoming the first private company to bring an advanced reactor to criticality under the Department of Energy’s Reactor Pilot Program. Criticality is the point where a nuclear fission chain reaction becomes self-sustaining. Fresh off a $470 million Series C funding round in July, Antares aims 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.

The Strategic Need for Space Nuclear Power

The award advances a push to launch nuclear reactors in space as early as 2028 and on the lunar surface by 2030, stemming from an executive order on “Ensuring American Space Superiority.” For the Space Force, the appeal of nuclear power is what it enables. Steady, always-on power allows spacecraft to maneuver without rationing every burn. It also supports heavy computing, directed energy, and electromagnetic warfare systems that solar panels cannot reliably power.

Bramble emphasized the company's broad vision. “Our tagline, from the company’s earliest days, has been ‘abundant energy from Earth to the asteroid belt,’” he said.

A Series of Defense Department Awards

The space nuclear contract follows several recent Antares wins across the DoD. The company's recent government awards include:

These contracts build on the company's foundational work. Antares has focused on a heat-pipe architecture designed for manufacturability and practicality both on Earth and in space.

The US has flown only one nuclear reactor in space, the SNAP-10A in 1965. Antares now aims to be the second. Bramble framed the latest award as part of a renewed focus on American space superiority. “It will take American ingenuity and American hardware to get there,” he said.