Space nuclear reactor secures $161M defense deal to end 60-year orbital power gap

The US has not operated a nuclear reactor in space since 1965. Antares now wants to change that with a $161 million defense award. The nuclear microreactor startup has won a Strategic Breakthrough award from the US Space Force. It will use the funding to advance nuclear power systems for future space missions. The award ranks among the largest current US defense investments in space nuclear power. It also gives Antares a path from reactor testing on Earth toward a potential flight system. The program could eventually give spacecraft a persistent source of electricity. That matters as military satellites demand more computing power and advanced onboard systems. Reactor built for space Antares will first demonstrate its R1-S reactor design on the ground. Engineers will then integrate the system with a spacecraft for flight certification before launch. The R1-S uses heat pipes to move heat away from its nuclear core. That design avoids many mechanical components found in conventional cooling systems. Antares also plans to use its Mark-1 reactor for an operational ground-to-space system. Testing is scheduled to begin in 2027. Mark-1 will generate electricity through a closed Brayton cycle power system. Antares expects the reactor to operate for more than six months during that test campaign. The company sees nuclear power as more than an energy source. A reactor could give spacecraft greater freedom to maneuver without quickly exhausting limited power reserves. Continuous electrical output could also support heavier computing workloads and directed-energy systems. Those capabilities could become increasingly important as military operations move into more contested orbital environments. Antares already crossed milestone Antares reached a major reactor milestone earlier this year. Its Mark-0 microreactor achieved initial criticality at Idaho National Laboratory on June 4. Initial criticality means the reactor sustained a self-supporting nuclear fission chain reaction. The Department of Energy authorized the test under its Reactor Pilot Program. That milestone made Antares the first private company to achieve advanced-reactor criticality under the program. It also gave the startup practical operating experience before its larger Mark-1 test. The timing adds momentum to the space effort. Antares raised $470 million in a Series C financing round in July. CEO and co-founder Jordan Bramble said the company has pursued space applications since its founding. He described the award as the point where that ambition became an official mission. The broader US effort also has a firm policy target. Executive Order 14369 calls for nuclear reactors in space as early as 2028. A separate national initiative calls for nuclear power on the lunar surface by 2030. Those goals would require reliable systems that can survive launch and operate far from conventional power infrastructure. Sixty-year gap The US has only flown one nuclear reactor in space. NASA launched SNAP-10A in 1965 as an experimental nuclear power system. More than six decades later, Antares is pursuing a very different generation of reactor. Its systems target military spacecraft that need sustained electrical power and greater operational flexibility. Success would give the US another nuclear reactor in orbit after an extraordinary gap. The next challenge is proving that a compact terrestrial reactor can meet the demands of launch and space operations.Get the latest in engineering, tech, space & science - delivered daily to your inbox.Aamir is a seasoned tech journalist with experience at Exhibit Magazine, Republic World, and PR Newswire. With a deep love for all things tech and science, he has spent years decoding the latest innovations and exploring how they shape industries, lifestyles, and the future of humanity.