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Propulsion & Power

Antares wins $161m award to demonstrate space nuclear reactor

By SpaceEnergy 11 September 2026 1 min read

(SpaceEnergy) Antares has won a $161 million US Space Force-related award to ground-demonstrate its R1-S nuclear reactor and integrate the system with a spacecraft for flight certification.

The company said the Strategic Breakthrough award was made by the Office of the Assistant Secretary of the Air Force for Space Acquisition and Integration and represents the largest current US defence award for space nuclear power.

Under the programme, Antares will conduct a nuclear ground demonstration of the R1-S and integrate it with a spacecraft ahead of flight qualification and launch. The company will also use its Mark-1 electricity-producing reactor to power an operational ground-to-space asset.

Mark-1 testing is scheduled for 2027, with Antares targeting operation for more than six months using its nitrogen closed-Brayton-cycle power-conversion system.

“Fission will unlock strategic capabilities that are impossible today,” chief executive and co-founder Jordan Bramble said.

Antares said space nuclear power could provide persistent electricity for high-compute spacecraft and reduce power constraints on propulsion and manoeuvring.

The company’s Mark-0 microreactor achieved initial criticality at Idaho National Laboratory on 4 June under US Department of Energy authorisation. Antares said the new award supports US policy objectives for nuclear-reactor launches in space as early as 2028.

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