DOD funds $161 million space reactor award

Antares announced that it has received a $161 million award from the Department of Defense to demonstrate a nuclear reactor and integrate it with a spacecraft for flight certification.

The company said it will be demonstrating a reactor that it calls R1-S, which stands for R1-Space. Antares told Nuclear News that the design is adapted from the architecture of the company's R1 microreactor, which its website describes as being "inspired by historical space reactor designs."

"This design is adapted from the same architecture as our flagship R1, but it is not based on any previous space reactor designs. With that said, the R1-S relies on mature components that have been demonstrated in previous space reactor concepts, including sodium heat pipes, moderator blocks, control drums, and a closed Brayton cycle," said an Antares representative. "The R1-S has a similar architecture as the R1 but utilizes different materials and operating regimes. Block 1 of the system will be targeting 35 kWe-plus. Like the R1, it has control drums, shielding (in a different form factor for space/mass savings), and a nitrogen closed Brayton cycle. The heat rejection system is very different for radiating heat into space."

Antares achieved zero-power criticality with Mark-0, a forerunner to the R1 with no power conversion or heat removal systems, in June through the Department of Energy's Reactor Pilot Program. The company is now working on Mark-1, its electricity-producing R1 prototype, which it said is scheduled to operate for more than six months in 2027 while integrated with Antares's nitrogen closed Brayton cycle power conversion system.

"Space has been core to the Antares thesis since the company was founded," said Jordan Bramble, the company's CEO and cofounder. "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."

Other recent projects: While Bramble has expressed Antares's space ambitions in the past, the company has also been pursuing projects that will stay on Earth.

Antares was recently selected to be paired with North Carolina's Fort Bragg for the Department of the Army's Janus Program, which aims to bring Army-regulated reactors on line at military installations by September 2028.

The company was also selected to deploy a reactor at Joint Base San Antonio in Texas through the DOD's Advanced Nuclear Power for Installations program.