US start-up Antares Nuclear has raised $470m in Series C funding, co-led by Paradigm and Caffeinated Capital, with participation from Point72 Ventures, Shine Capital, Industrious Ventures, and others. The capital, which includes $370m in equity and $100m in debt, comes weeks after Antares achieved initial criticality of its Mark-0 microreactor under the DOE Reactor Pilot Program. Mark-0 was the first of four advanced reactors racing to go critical by the 4 July deadline set by President Trump in his May 2025 Executive Order (EO) 14301, Reforming Nuclear Reactor Testing at the Department of Energy.
Antares was founded in 2023 to mass-manufacture micronuclear reactors. It is staffed primarily by aerospace, defence, and nuclear experts recruited from disruptive hardware environments like SpaceX, Relativity Space, and the US Air Force. The company previously closed a $96m Series B funding round in December 2025, which included $71m in equity led by Shine Capital and $25m in debt. Before that, Antares raised $30m in a Series A round in 2024. Antares is now backed by over $600m in funding and has raised millions in government defence contracts.
In Torrance, California, Antares operates a 145,000-square-foot facility optimised to mass-produce up to 10 factory-sealed microreactor units a year. It also has offices in Idaho Falls and Aiken, South Carolina. The company bypasses conventional commercial timelines by framing its reactors as vital defence assets.
Antares has established a highly focused, committed military order book by positioning itself to resolve a critical defence vulnerability: military bases relying on vulnerable commercial energy grids. The company’s existing US military contracts and project selections span several key initiatives.
In April, Antares was selected for a proposed deployment of a nuclear microreactor under the Advanced Nuclear Power for Installations (ANPI) programme. The reactor is slated for installation at Joint Base San Antonio (JBSA). It will field a container-sized, autonomous microreactor generating between 100 kW and 1 MW of power to act as resilient, off-grid infrastructure against extreme weather or adversary targeting.
A $4.2m firm-fixed-price definitive contract was awarded to Antares by the Air Force Research Laboratory (AFRL) in January. This was for research and development for nuclear electric propulsion under the NEPADSO initiative. The goal is to build nuclear-powered systems that provide sustained endurance and rapid maneuverability for military spacecraft in contested space environments. This was funded under the Air Force’s nuclear-related technical and propulsion research pipelines to scale hardware capabilities ahead of mid-2026 testing milestones.
Antares was chosen in April 2025 as one of eight advanced nuclear suppliers by the Defense Innovation Unit (DIU), the Department of the Army, and the Department of the Air Force. This gave Antares the direct eligibility to receive Other Transaction (OT) awards to rapidly design and deploy fixed on-site microreactor technology across multiple global Department of War (DOW) installations.
In 2024, Antares executed various Phase I and Phase II Small Business Innovation Research (SBIR) contracts with AFRL. These early-stage awards paved the way for heavy hardware development, specifically targeting rapidly deployable microreactors for tactical Air Force use cases.
In co-operation with DOW and the US Army, Antares is a leading vendor for the Janus Program launched in October 2025 that aims to systematically deploy commercial nuclear microreactors across domestic military installations to achieve absolute energy resilience.
Currently Antares is looking to satisfy the mandate of Executive Order (EO) 14299, Deploying Advanced Nuclear Reactor Technologies for National Security, signed into law in May 2025. This explicitly instructs DOW to begin the operation of an advanced nuclear reactor, regulated directly by the US Army, at a domestic military base by 30 September 2028.
The EO created the regulatory and financial framework for programmes such as the ANPI project and Project Janus. By legally forcing federal agencies to bypass standard commercial grids for critical infrastructure, it established a guaranteed, government-backed market for microreactor startups such as Antares, capable of meeting the strict 2028 deployment window.
“On June 4th, we won the race to criticality, and now we’ve shifted to the race to commercialisation,” said Antares CEO Jordan Bramble. “The military has been a partner to us every step of the way. We’ve secured firm contracts to build reactors. To do that, we’re announcing $470m of equity and debt to invest one-to-one with the taxpayer in bringing this technology to commercial scale. Our deep customer relationships and committed orderbook allow us to focus our engineering roadmap on one simple thing from here on out – reactors that operate reliably and safely for 6+ years deployed to military installations as soon as 2028. This focus will guide us to the first microreactor producing useful electricity in a truly commercially viable design.”
