In the Pentagon’s vision of future warfare, energy is becoming as decisive as weapons.

Earlier this month, the Defense Advanced Research Projects Agency quietly awarded $5.2 million to Avalanche Energy, a Seattle‑based fusion startup, to develop ultra‑compact nuclear power systems—devices sometimes described as nuclear batteries. They are not reactors, and they don’t generate megawatts. Instead, they promise something more subversive: steady power, for years, where logistics fail and sunlight never reaches.

The project sits inside DARPA’s Rads to Watts program, a push to bridge the gap between conventional batteries and full‑scale nuclear systems. The goal is deceptively modest: convert radiation from radioisotopes directly into electricity using micro‑fabricated semiconductor cells. The ambition, however, is strategic.

Power Where Nothing Else Works

Modern militaries increasingly rely on systems that operate far from supply chains—deep‑space assets, autonomous sensors, undersea platforms, and remote forward installations. In those environments, lithium batteries degrade, fuel resupply is risky or impossible, and solar power is unreliable or nonexistent.

Radioisotope power systems offer a different equation. Avalanche’s approach converts the energy of alpha particles—high‑energy charged particles emitted during radioactive decay—directly into electrical current. The company compares the process to photovoltaics: instead of light striking a solar cell, radiation strikes a solid‑state converter.

Program targets cited by Avalanche include energy densities exceeding 10 watts per kilogram, enough to power low‑energy electronics for months or years using systems that are small, sealed, and lightweight. That may not sound revolutionary—until you realize that endurance, not peak output, increasingly defines military advantage.

Why DARPA Cares

DARPA is not chasing commercial gadgets. It is testing whether such systems can survive extreme radiation environments without degrading—historically the Achilles heel of radiovoltaic technologies. Semiconductor damage, heat buildup, and declining conversion efficiency have long limited nuclear battery concepts.

Avalanche’s contract focuses less on deployment and more on durability: do materials and microstructures exist that can reliably harvest energy from radiation over long durations? The work will involve academic and national‑lab partners, including the University of Utah, Caltech, and Los Alamos National Laboratory. [geekwire.com]

This is classic DARPA territory: high‑risk physics with outsized strategic payoff.

The Fusion Connection

Although the immediate project uses radioisotopes, its long‑term implications extend to fusion—a technology that has spent decades perpetually “ten years away.”

Fusion reactions produce not just heat, but energetic charged particles, including alpha particles. If those particles could be captured directly and turned into electricity, fusion systems could bypass turbines, steam cycles, and some of the efficiency losses that plague today’s designs.

Avalanche argues that the same materials and structures needed to convert radiation into electricity today could eventually enable direct energy conversion from fusion reactions tomorrow.

In other words, nuclear batteries are not a detour from fusion—they may be a prerequisite.

A Quiet Shift in Defense Energy Strategy

The Pentagon has backed nuclear power before, from aircraft carriers to space probes. What is changing now is scale. Rather than a few massive reactors, DARPA is exploring distributed nuclear power—small, modular, long‑lived systems embedded deep inside platforms and networks.

This reflects a broader shift in defense R&D toward endurance over intensity, sustainment over surge. Energy is no longer just a support function; it is becoming a strategic enabler.

Still Early—and Still Uncertain

None of this guarantees success. The technology remains at a laboratory stage, and initial demonstrations will focus on physics validation rather than deployable hardware. Nuclear safety, regulatory complexity, and manufacturing challenges all loom.

But the significance lies in the direction of travel.

Between batteries and reactors, between today’s systems and tomorrow’s fusion promises, DARPA is carving out a narrow but potentially transformative middle ground. If it works, the Pentagon will not just have a new power source—it will have rewritten how energy underpins military power in the 21st century.

‍