WASHINGTON — Zeno Power Systems was awarded a $30 million contract to build a radioisotope-powered satellite for the U.S. Air Force by 2025.

The four-year contract is a “strategic funding increase” agreement that provides $15 million in government funds, matched by $15 million from private investors, the company’s co-founder and chief executive Tyler Bernstein told SpaceNews.

Zeno, a startup founded in 2018, develops radioisotope power systems (RPS), a type of nuclear energy technology that converts the heat from decaying nuclear materials directly into electricity. 

Bernstein said the company designed an RPS concept for small satellites with the goal of making the technology more accessible. NASA for decades has used RPS to power deep-space probes but the technology has not been commercialized due to cost and high regulatory hurdles.

Zeno’s RPS is smaller and uses lower-materials. Bernstein expects the system to clear regulatory hurdles and be approved for launch in 2025, taking advantage of a more streamlined U.S. government review process for nuclear-powered space missions. 

The company pitched the RPS idea to the Air Force Research Laboratory in 2019 and won several small business innovation research contracts. The STRATFI agreement was signed in August 2022.

Bernstein called the STRATFI deal a “key validation” of RPS as a viable technology to power military spacecraft. To fund its share of the project, the company will draw from its $20 million in Series A venture capital raised last year. 

The military wants satellites that can maneuver without having to worry about running out of fuel, Bernstein said. RPS would support that goal.

Lt. Col. Thomas Nix, U.S. Space Force project manager at AFRL, said the technology would “enable constant maneuverability between different orbits, unlocking new capabilities for the Department of Defense.”

Satellites would have “always on” power for years at a time, Nix said. 

How RPS works

Bernstein cautioned that RPS should not be confused with nuclear electric propulsion that relies on fission reactors. 

“We are not a fission reactor. We’re a radioisotope source,” he said.

RPS is more akin to a nuclear battery that uses the heat generated by the decay of a radioactive isotope to produce electricity.

“It’s really hot rocks in a box,” said Bernstein. 

Radioisotopes decay over decades and produce heat. Zeno developed a method to capture that heat and convert it to electricity using a solid state device called thermoelectric generator. The difference in temperature between the hot interior and the cold vacuum in space creates electricity. 

A small device the size of a shoebox generates electricity for decades, Bernstein said. 

A key feature of Zeno’s system is that it does not rely on plutonium.

NASA’s planetary missions use RPS fueled by plutonium 238 isotope, which is in short supply and not commercially available. The Department of Energy produces only enough plutonium 238 to support key NASA missions.

The Air Force in the past has used the isotope strontium-90 as a power source but its applications were limited due to its large mass and low efficiency.

Zeno’s RPS uses strontium isotope with a novel design that results in a lighter weight heat source. Bernstein said the company is exploring the use of other isotopes in the future.

The first demonstration of Zeno’s RPS heat source will take place this summer at a Department of Energy lab. 

RPS illustration. Credit: Zeno Power Systems

Regulatory hurdles 

The deployment of a satellite powered by small nuclear batteries typically would face enormous regulatory obstacles but the approval process was made easier by a 2019 executive order from the Trump administration that overhauled the launch approval process for space nuclear systems.

Before that policy change, there had been only one process to approve launches of any spacecraft with nuclear power systems, regardless of its makeup and size. 

The 2019 order established a three-tier system for reviewing payloads carrying nuclear power systems based on the amount of radioactive material on board and the probability of certain radiation exposure levels in the event of an accident. The approval process also looks at de-orbiting procedures at the end of the mission life. 

Spacecraft that fall in the first two tiers can be approved by their sponsoring agency and an interagency panel, and only the highest-risk third tier missions require presidential authorization. 

Bernstein said the lower-tier missions can now work through the Federal Aviation Administration, “for the first time allowing a commercial entity to launch a nuclear power system spacecraft into space.” Zeno is pursuing launch approval as a tier-one mission.

Earlier this year, Zeno’s payload review application was accepted for review by the FAA, said Bernstein, and a launch approval could come as early as 2025. 

The company’s focus is to qualify RPS for small satellites that the Space Force would deploy, but commercial applications also are envisioned. 

“We see opportunities in the lunar space economy,” Bernstein said. “Right now all the landers that are going to the lunar surface are going to operate for 14 days during the lunar day and freeze during the lunar night.”

“We are at the dawn of the commercial space nuclear era,” he said. RPS would provide enough heat and power so landers can operate for years and “enable a sustainable lunar economy in the future.”

How it started

Zeno Power today has 25 employees based in Seattle and in the Washington, D.C. area. 

The other co-founders are Jonathan Segal, who is chief operating officer; and Jacob Matthews, chief technology officer. 

The three met at Vanderbilt University where Bernstein and Segal were undergraduates. Matthews was a graduate of the U.S. Military Academy at West Point working on a master’s degree in mechanical engineering focused on RPS technology for space. 

“We got together and started pursuing this back in 2018,” Bernstein said. 

Zeno’s vice president of strategic partnerships, Tim Frazier, previously ran the Department of Energy’s RPS program and helped build NASA’s Cassini and New Horizons missions. 

Another executive at the company, Lindsey Boles, is a former director of engineering at TerraPower, a nuclear reactor design and development company founded by tech billionaire Bill Gates. 

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...