How Antares is Building Fission Microreactors, Enabling Strategic Energy for Critical Mission Capabilities on Earth, In Space, and Underwater

Antares, building purpose-designed modular power for defense-critical assets, led by Jordan Bramble and Julia DeWahl, has secured $96 million in Series B led by Shine Capital with participation from Alt Capital, Caffeinated, 53 Stations, Industrious Ventures, and others.

The capital provides the momentum and discipline needed to achieve a milestone not seen in the United States for decades: the ability to design, build, and test nuclear reactors within a few years rather than over the course of decades.

The purpose behind raising this capital, the capabilities it unlocks, and the role it plays in a far larger mission can be stated clearly.

Antares, founded just over two years ago, emerged from several urgent observations:

• Energy scarcity is constraining the deployment of critical U.S. national security systems.

Paradigm shifts in warfighting have created environments where the U.S. military lacks access to the electrons required for next-generation capabilities.

• The nation lost the ability to build nuclear hardware quickly and iteratively.

For nearly half a century, nuclear engineering became an exercise dominated by paperwork, modeling, analyses, and reviews—performed largely without the develop–build–test–iterate cycles essential for maturing real systems. Entire generations of engineers retired without ever constructing or operating the hardware they spent careers designing.

The newly raised capital is intended to redirect that trajectory.

The funding will support hardware development, subsystem testing, fuel fabrication, manufacturing, and the infrastructure needed to activate a reactor and establish the groundwork for continued progress. Modern nuclear systems demand that design and build proceed in tight iterative loops rather than as separate, linear phases.

In 2026, a low-power reactor demonstration, the Mark-0, will be conducted at Idaho National Laboratory. Enabled by Executive Order 14301: Reforming Nuclear Reactor Testing at the Department of Energy, this demonstration will validate the reactor physics and reactivity controls of the R1 design and establish the facility, tooling, and operations required for sustained testing. Critically, it will also accelerate the development of institutional expertise with the DOE-1271 authorization standard, enabling faster and more predictable future test campaigns.

Following the successful completion of Mark-0 operations, the next major milestone is the construction of a full-power, electricity-producing reactor as early as 2027, using the same Idaho facility. In 2026, efforts will shift from reactor physics tests to qualifying the full suite of reactor subsystems and constructing the first commercial prototype microreactor, the Mark-1.

The Mark-1 reactor will serve as the bridge between development and production, validating:

• System performance under expected operating conditions at full power and temperature for at least 90 days.

• Power conversion capabilities for real-world electricity production through a closed Brayton cycle system, following initial testing of the first unit in 2026.

• Safety across all phases and operating states, including passive and inherently safe design features.

• Operational procedures, including startup, shutdown, and decommissioning.

The capital raised positions Antares to compete in sector-defining federal programs across the Department of the Army, NASA, and other agencies.

In October, the Army announced the JANUS program, a microreactor-focused initiative aimed at delivering resilient, secure, and assured energy to support bases and operational missions. JANUS represents a significant step in transitioning from prototypes to commercially viable microreactor solutions for warfighters, making the Department the first moving customer in advanced nuclear. The initial microreactors delivering power in the U.S. are expected to be deployed on military installations.

NASA’s Fission Surface Power program, targeting a 100-kWe reactor on the lunar surface by 2030, aligns with Antares’ manufacturing capabilities and design expertise, supporting the development of a space-based industrial economy.

These programs highlight a critical reality: safe, reliable, 24/7 energy is essential across Earth, space, and underwater domains to ensure national security and maintain global leadership.

The long-term goal is simple: abundant energy throughout the Solar System. Antares is building the engineering prime of strategic energy, delivering complete fission-powered solutions to military, NASA, and other federal, commercial, and allied partners. The focus is on enabling high-value mission capabilities, rather than simply providing a “box of power” to replace diesel generators.

This fundraise advances that vision, providing the facilities, fuel, and team to execute one of the fastest and most consequential nuclear development timelines in modern history. The path ahead is challenging, but the team remains clear-eyed and focused on the work required.

Antares looks forward to continuing collaboration with government and commercial partners, building systems that revitalize American industrial capacity and reinforce technological leadership.