Antares Wins $161M Space Force Award to Demonstrate Nuclear Reactor in Orbit

Antares has been selected for a $161 million Strategic Breakthrough award to advance nuclear power for space, the company announced September 11. The selection, made by the Office of the Assistant Secretary of the Air Force for Space Acquisition and Integration, marks the largest current Department of War award in space nuclear power.

The award directs Antares to carry a nuclear-powered spacecraft toward flight qualification. It supports goals set in Executive Order 14369, "Ensuring American Space Superiority," and the National Initiative for American Space Nuclear Power established by NSTM-3, which call for launching nuclear reactors in space as early as 2028 and on the lunar surface by 2030.

Under the program, Antares will perform a nuclear ground demonstration of the R1-S reactor and integrate it with a spacecraft for flight certification prior to launch. The company will also power an operational ground-to-space asset with Mark-1, its electricity-producing reactor, which is scheduled for testing in 2027. The Mark-1 is set to operate for more than six months in 2027, integrated with a nitrogen closed Brayton cycle power conversion system.

The award follows a milestone earlier this year. On June 4, 2026, the company's Mark-0 microreactor achieved initial criticality at Idaho National Laboratory under Department of Energy authorization, making Antares the first private company to bring an advanced reactor to criticality under the DOE Reactor Pilot Program.

"Space has been core to the Antares thesis since the company was founded," said Jordan Bramble, CEO and co-founder of Antares. "This partnership with the Space Force turns that long-held vision into a codified space mission. Fission will unlock strategic capabilities that are impossible today."

According to the company, space nuclear power removes propulsion constraints for the Space Force, allowing spacecraft to maneuver without regret and carry out dynamic operations that were once impossible. Antares states the technology brings high, always-on power to support heavier compute loads, directed energy systems, and the future of electromagnetic warfare.

The next milestones named by Antares are the testing of its Mark-1 reactor in 2027 and the reactor's planned operation for more than six months that year. The broader initiative directs the launch of nuclear reactors in space as early as 2028 and on the lunar surface by 2030.