Antares Secures $96M to Power US Defense and Space Microreactor Race

WASHINGTON, DC – December 02, 2025 – In a significant move that underscores growing investor and government confidence in advanced nuclear power, startup Antares has closed a $96 million Series B funding round. The capital injection, led by Shine Capital, is set to accelerate the company’s ambitious timeline to demonstrate a functional fission reactor by 2026—a feat no private startup has achieved this century. This positions Antares as a critical contender in the high-stakes race to develop compact, portable nuclear microreactors for national security, space exploration, and critical industrial applications.

The funding round, comprised of $71 million in new equity and $25 million in debt, is not merely a vote of confidence but a strategic allocation of resources. The capital is earmarked for tangible milestones: procuring specialized equipment, completing the build-out of its 145,000-square-foot factory in Torrance, California, and securing a supply of the High-Assay Low-Enriched Uranium (HALEU) fuel essential for its advanced design. For a company just over two years old, this infusion brings its total capital raised to over $130 million, providing the necessary fuel to transition from design to demonstration.

“This funding marks a major milestone for Antares,” said CEO Jordan Bramble in a statement. “We’re months away from our first reactor demonstration, which will validate our control systems and neutronics models... We’ve raised the capital we need to mobilize to provide resilient energy for our partners at the Department of War (DoW) and NASA.”

Alex Hartz, General Partner at Shine Capital, highlighted the rarity of Antares' progress. “No nuclear startup has turned on a fission reactor this century. Antares is poised to achieve this milestone in 2026, thanks to their design and licensing maturity, fuel supply chain, and swift progress in demonstrating the performance of its underlying components.”

The Technology: A Reactor in a Shipping Container

At the heart of Antares' strategy is its R1 Microreactor, a technology that reimagines nuclear power not as a sprawling plant but as a compact, rapidly deployable energy source. Designed to fit within a standard shipping container, the R1 aims to generate 200 to 300 kilowatts of electricity—enough to power a remote military outpost or a small industrial site—for over three years without refueling.

The design leverages key innovations for safety and efficiency. It uses TRISO coated particle fuel, widely regarded for its robustness, within a prismatic graphite core. Cooling is achieved passively through sodium heat pipes, a design choice that eliminates the need for pumps and reduces mechanical complexity, thereby enhancing reliability. Power is generated via a nitrogen Brayton cycle, a closed-loop gas turbine system known for its high efficiency in compact applications.

This technical approach has been validated through critical partnerships. A recent electrically-heated demonstration of the reactor core, conducted with NASA's Marshall Space Flight Center, provided crucial data. Furthermore, ongoing collaborations with Idaho National Laboratory (INL) and Oak Ridge National Laboratory are verifying the core's neutronics and thermal hydraulics, lending institutional credibility to the company's aggressive development timeline. This multipronged validation strategy is essential for de-risking the technology ahead of its planned 2026 low-power test and 2027 full-scale electricity-producing prototype.

The Strategic Market: Powering Defense and Deep Space

Antares' business model is sharply focused on markets where energy resilience is not a convenience but a strategic necessity. The company has already secured contracts with the U.S. Air Force, Space Force, and the Defense Innovation Unit (DIU), signaling deep alignment with national security priorities.

In April, the DIU selected Antares under its Advanced Nuclear Power for Installations (ANPI) program, which aims to deploy microreactors at military bases to ensure energy continuity, independent of vulnerable civilian grids. Antares' containerized, rapidly deployable design is particularly well-suited for the military's Agile Combat Employment (ACE) doctrine, which requires the ability to establish and power forward operating bases on short notice.

With this new funding, Antares is also poised to compete for the U.S. Army's newly established JANUS program. Announced in October, JANUS formalizes the Army’s pursuit of advanced nuclear energy, targeting reactors in the kilowatt-to-20-megawatt range. Success in this program would represent a landmark contract, establishing microreactors as a core component of the Pentagon's energy infrastructure.

Beyond terrestrial defense, Antares has its sights set on the cosmos. The company plans to bid on NASA's Fission Surface Power program, which has the ambitious goal of placing a 100 kWe nuclear power source on the lunar surface by 2030 to support a sustained human presence. For missions to the Moon and Mars, where solar power is intermittent or insufficient, compact fission reactors are considered an indispensable enabling technology.

Navigating the Regulatory Fast-Track

Perhaps the most critical factor enabling Antares' speed is a shifting regulatory and policy landscape in Washington. For decades, the path to licensing a new nuclear reactor has been prohibitively long and expensive. However, recent government initiatives are creating a streamlined pathway for advanced reactor developers.

In August, Antares received two crucial boosts from the Department of Energy (DOE). First, it was granted an allocation of HALEU fuel, a material enriched to between 5% and 20% uranium-235 that is necessary for smaller, more efficient reactor designs. With no commercial domestic supply chain for HALEU yet established, these DOE allocations are a lifeline for the industry. Second, Antares was selected for the DOE's new reactor pilot program, which provides a federal authorization process for demonstrating reactors outside of national laboratories.

These programs, combined with the Nuclear Regulatory Commission's (NRC) ongoing work to develop a new, risk-informed regulatory framework (10 CFR Part 53) for advanced reactors, significantly de-risk the path to commercialization. While competitors like BWXT Advanced Technologies, which is building a mobile reactor for the DoD's Project Pele, and Westinghouse with its eVinci microreactor are also formidable players, Antares’ combination of a nimble startup culture, strong government partnerships, and a clear focus on specialized, high-margin applications gives it a distinct position in this burgeoning market. The 2026 criticality demonstration now stands as the company's next major test, a milestone that could very well signal a new dawn for nuclear energy in America.