Avalanche Energy Builds Desk-Sized Fusion Reactors for Defense and Remote Power
Instead of chasing giant reactors, this Seattle startup is building microwave-sized fusion systems—faster, cheaper, and military-ready
Fusion energy has long been seen as the crown jewel of clean power, offering virtually limitless, carbon-free electricity without the radioactive waste of traditional nuclear fission. But progress has been sluggish for decades. The typical fusion experiment takes years and billions of dollars to build, often in the form of colossal tokamaks or laser-based systems.
Avalanche Energy is betting that smaller is smarter. The Seattle-based startup is pursuing micro-fusion reactors compact enough to sit on a desk, driven by a conviction that fast iteration and modular design will deliver results faster than conventional approaches ever could.
Their strategy hinges on building, testing, and revising quickly, much like how early space startups approached rocket development. That nimbleness allows them to bypass the paralyzing cycles of over-analysis that often bog down large fusion projects.
"You simplify your models, and then when you put them in, we find you may sputter off ions and they deposit somewhere else," said Brian Riordan, co-founder and Chief Operating Officer at Avalanche Energy. "Or they build up charge on ceramics and change how your beam or confinement works… But we can turn it around and fix it. We move forward with 50% to 70% of the information, test it, and validate the model."
That flexibility means the team isn't afraid to break things. During one test, their ion injector malfunctioned spectacularly.
“It looked like a lightsaber stuck into the diagnostics,” Riordan said. But because their machinists could rebuild the part in a day, the disruption didn’t derail progress.
The Orbitron and the DTF Core
Avalanche’s fusion reactors are based on a proprietary design called the Orbitron. This system's heart is a high-vacuum chamber surrounded by a magnetic bottle. Inside, electrostatically confined ions race in elliptical orbits, crashing into each other at incredible speeds in the hope of fusing.
The company focuses on deuterium–tritium fusion (DTF)—a reaction in which a deuteron (a nucleus of heavy hydrogen) fuses with a triton (a nucleus of radioactive tritium), creating a helium-4 nucleus, a free neutron, and releasing 17.6 mega-electron volts (MeV) of energy. This is the most efficient and best-studied fusion reaction, widely used in fusion research and thermonuclear weapons.
Because tritium is radioactive and scarce, future reactors must produce it on-site. Fusion systems like Avalanche’s are expected to use breeding blankets—layers of lithium-containing materials that, when struck by fusion-generated neutrons, will yield fresh tritium.
Recently, Avalanche achieved a milestone by sustaining 300,000 volts in their device for five hours with negligible power leakage. “It was in the error of measurement of our power supply,” Riordan said, estimating energy losses below 20 microamps. “That voltage gets us the energy in the ions for a good cross section—it’s the peak cross section, well beyond it, for deuterium-tritium.”
In lay terms, they reached the energetic sweet spot where DTF has its highest chance of occurring.
Avalanche Energy: A Startup with Serious Backing
Founded in 2019, Avalanche quickly became a standout in the growing fusion startup space. Based in Seattle, the company is developing modular fusion micro-reactors that can be grouped to deliver scalable power from kilowatts to megawatts.
In April 2023, Avalanche raised $40 million in Series A funding from investors including Toyota Ventures, Founders Fund, Lowercarbon Capital, and Autodesk. Their technical milestones are equally compelling: They operated a prototype at 200 kilovolts, which is believed to be the highest known operating voltage for any fusion device since a 2006 experiment at the University of Wisconsin.
Their reactor, the Orbitron, isn’t just a concept—it’s actual hardware that has undergone several iterations. The company claims a test-fail-fix cycle that allows for physical changes in days, not months. “We’ve developed and operated two high-voltage reactor prototypes, achieving significant performance steps over the last 18 months,” said CEO Robin Langtry in an earlier statement.
The team has grown to around 50 engineers and physicists. Their expanded Seattle test lab now churns out working prototypes like “Marty” (from Back to the Future), “Neo” (from The Matrix), and “Camina” (from The Expanse)—each named after science fiction icons that reflect the company’s futuristic ambitions.
A Reactor on a DeLorean
Avalanche’s sci-fi inspirations aren’t just internal. They made technical and regulatory headlines when they mounted a mock-up reactor on the back of a Back to the Future-style DeLorean during a deep tech showcase in San Francisco.
The car was displayed at an event aboard the USS Hornet, an aircraft carrier turned tech venue. The replica time machine not only turned heads but also caught the attention of the U.S. Nuclear Regulatory Commission.
“My radiation safety officer came and told me that the Nuclear Regulatory Commission wanted to meet with us because they heard about a reactor on a car,” Riordan recounted. “That was alarming, and I didn’t know what was happening.”
The NRC’s concern eased after they learned it was only a demo, not a functioning device.
“We laughed, and they didn’t know why we were laughing,” Riordan said. The confusion was eventually cleared up, but it highlighted how seriously Avalanche is taken, even when showing off a pop culture homage.
The Case for Military First
Avalanche isn’t aiming at the power grid just yet—and that’s by design. Riordan argued that early fusion applications should mirror how technologies like GPS, MRIs, and even the Internet evolved, starting with defense.
“You start at low production, high cost… fusion is not going to be any different,” he said. He cited ARPANET (Advanced Research Projects Agency Network), the Defense Department’s original computer network and the precursor to the internet, as an example of how technologies mature in specialized, government-funded environments before becoming ubiquitous.
“The scary thing about the grid is—it’s a commodity,” Riordan said. “Most people like fusion. But look, I just want the light to go on. I can’t tell if it’s fusion electrons that showed up.”
Instead, Avalanche targets remote and defense uses where compact reactors offer unique advantages. Riordan pointed to autonomous underwater vehicles as an early use case.
“They don’t have another good way to get power or space,” he said. “So those remote applications are the first ones.”
Before even those, he added, "neutrons for imaging and remote sensing" could provide the earliest revenue streams.
Next: Scale, Speed, and Space
Avalanche Energy’s ambitions don’t stop at record voltages or pop culture cameos. With backing from the Defense Innovation Unit, the company is exploring applications for spacecraft propulsion and long-duration missions—places where traditional batteries or solar power can’t go.
To achieve this, they’ll continue building and testing next-generation Orbitron prototypes. This means miniaturizing key components, refining their power conversion systems, and scaling up production for small-scale commercial and defense deployment.
It’s a long road ahead. But by embracing rapid iteration and the belief that small is beautiful, Avalanche is carving a new path that might lead to practical fusion power, not in decades, but in years.