Antares secures DOE safety approval for space-linked nuclear reactor

(SpaceEnergy) Antares has secured US Department of Energy approval of a nuclear safety agreement for its Mark-1 microreactor, advancing a terrestrial power system linked to the company's military space programme.

The company announced on 23 October that the Department of Energy (DOE) had approved the Nuclear Safety Design Agreement (NSDA) for Mark-1, its first electricity-producing reactor.

The approval establishes design requirements, safety analysis procedures and regulatory expectations governing the reactor's development, construction and operation.

Mark-1 is scheduled to undergo several months of full-power testing at Idaho National Laboratory in 2027, using a nitrogen closed Brayton-cycle power conversion system.

The reactor incorporates the same full-scale core and tristructural isotropic (TRISO) fuel technology as Antares' Mark-0 demonstration reactor, which achieved criticality on 4 June 2026.

The development has a specific connection to the company's space nuclear programme.

Under a separate $161 million US Air Force Strategic Breakthrough award announced on 11 September, Antares is developing its R1-S space reactor towards flight qualification.

The company also identified Mark-1 as the intended electricity source for an operational ground-to-space asset associated with that programme.

Mark-1 itself is a terrestrial reactor and should not be confused with the R1-S spacecraft reactor.

Antares said the Mark-1 testing campaign would support subsequent deployments to defence customers, including a planned installation at Fort Bragg, North Carolina, in 2028.