A startup’s $5.2 million defense contract targets the most energetic nuclear decay particle, and bench tests show a solid state chip converting alpha emissions directly into electricity for space hardware
Deep inside a compact laboratory, a chip no larger than a fingernail sits above a radioactive source and does something no commercial battery can.
It catches nuclear decay particles in flight and converts them straight into current.
No turbine. No heat exchanger. No moving parts.
Beta particles are relatively easy to manage around people, and that safety profile made them the default choice for pacemaker batteries and deep space probes alike.
The device is an alphavoltaic cell, and a portable fusion startup just secured a federal defense contract worth just over five million dollars to prove it can work at kilowatt scale.
So how, exactly, does a semiconductor chip turn the most hazardous decay particle into usable power?
Why alpha particles carry so much energy and why nobody tried this before
Radioactive batteries have existed for decades, but almost every one runs on beta particles, electrons fired from a decaying nucleus at high speed. Beta particles are relatively easy to manage around people, and that safety profile made them the default choice for pacemaker batteries and deep space probes alike.
Alpha particles are a different matter. Each one is a dense cluster of two protons and two neutrons, roughly 7,000 times heavier than an electron, carrying far more kinetic energy per particle than a beta emission does. That energy density advantage is the whole point of the Rads to Watts program, which aims to turn high-power nuclear radiation into kilowatts of usable electricity.
The barrier was never energy. It was stopping distance. An alpha particle travels only an inch or two in air before losing all momentum and becoming inert. That short range turns out to be exactly what an alphavoltaic cell needs: the particle deposits nearly all its energy inside a thin layer of solid material, where a semiconductor junction captures it as usable current.
A chip built for the harshest address in the solar system
The cells under development are solid state and microfabricated, with no moving parts, no liquid and no heat exchanger. The result, if it works at scale, would be a power source sitting somewhere between a conventional nuclear battery and a miniature reactor, smaller than either and potentially far more power dense than both.
Space is the natural home for this technology. Alpha particles are easily blocked by thin shielding, and a few millimeters of spacecraft wall provide more than enough containment. What space cannot tolerate is weight, volume and mechanical complexity, and an alphavoltaic chip has none of those problems.
Remote planetary sensors, deep space probes and hardware that must operate for years without maintenance are all obvious candidates. Solar panels lose effectiveness past Jupiter; chemical batteries drain; alphavoltaic cells keep converting decay into current regardless of distance from the sun.
From portable fusion to nuclear decay, and what the pivot reveals
The company differentiates itself by building portable fusion reactors, machines meant to move rather than anchor to a fixed grid connection. That focus on compactness makes the alphavoltaic contract a logical extension: the underlying challenge is identical in both cases, extracting nuclear energy from a very small volume and delivering it as reliable electricity without conventional infrastructure.
Conventional radioisotope power systems, like the ones that have driven Mars rovers and deep space probes for half a century, produce watts to tens of watts. Current nuclear batteries used on Mars rovers provide only about 2.5 watts per kilogram. The kilowatt scale target embedded in the defense program represents an order of magnitude leap, making these devices relevant not just to scientific instruments but to propulsion, communications and active thermal management in space.
Whether the alphavoltaic approach can reach that target at acceptable mass and cost remains an open question. According to the company’s release, the solid state design eliminates several failure modes, but alpha emitters intense enough to generate kilowatts present handling challenges that bench scale demonstrations have not yet had to face.
The staggering energy density hidden in a particle you cannot see
A single alpha particle carries roughly 5 to 9 million electron volts of kinetic energy, compared with a few hundred thousand for a typical beta emission. A gram of a strong alpha emitter can release more energy in an hour than most chemical reactions manage in a day. That flux, packed into a microfabricated junction, produces a power density no battery chemistry and no solar cell can approach in the same volume.
The program’s target makes the ambition concrete. The system aims to deliver more than 10 watts per kilogram, enough to continuously power a laptop-class system for months from a device weighing only a few kilograms, while holding up in the radiation environment of space. The short stopping distance also means almost no radiation escapes the device. Alpha particles are absorbed by the very semiconductor layer that converts them, leaving almost nothing for external containment to handle, a fundamentally different safety profile from a gamma or neutron source.
For more on experimental approaches to extracting energy from unexpected nuclear phenomena, see our piece on single atom engine research.
What comes next, and where the gaps are still real
The Rads to Watts award is a development contract, not a production order, and the gap between a research program of this size and a flight ready power module is long and expensive. Materials that hold up to sustained alpha bombardment without degrading their semiconductor junction are a known challenge; the same particle flux that deposits energy can damage the crystal structure of the converter over time, gradually reducing output.
That degradation curve will need to be characterized through material selection and device architecture choices still being worked out. The work connects to a broader federal push to develop novel extraction methods well outside conventional engineering pathways.
Even so, the direction of travel is clear. As demand grows for long duration, maintenance free power in extreme environments, driven by commercial space ambitions and remote grid edges alike, the pressure to find something better than chemical batteries will only intensify. An alphavoltaic chip that delivers kilowatts without fuel lines, without moving parts and without a sun to point at would answer a question the energy industry has been asking, quietly, for decades.
Hugo is an engineer with strong technical expertise. Multilingual from an early age, his writing combines technical clarity with a strong interest in science and energy.
