In a strong indication of the Pentagon’s growing ambitions for a lasting foothold beyond Earth, the Defense Advanced Research Projects Agency (DARPA) recently unveiled early plans for a groundbreaking technology program. The initiative aims to develop compact, long-duration nuclear power systems that could one day energize permanent off-world outposts or support long-range missions deep into space.
The program, “Rads to Watts,” was recently outlined in a Special Notice and Future Program Announcement issued by DARPA’s Defense Sciences Office. While the announcement is framed as an exploratory call for research, carefully reading between the lines reveals a far more ambitious vision.
Central to the initiative is transforming how nuclear energy is converted into electricity by moving beyond conventional heat engines and into the realm of “radiovoltaics,” or solid-state devices that directly convert radiation into power.
If successful, the technology could provide a constant stream of power in harsh, power-starved conditions, such as permanent off-world installations or deep space surveillance platforms.
“Enabling the operation of radiovoltaics at higher radiation fluences will enable long-lived, unattended high-power sources for new operating domains that are power-starved and/or for which a logistics supply chain to replenish power sources does not exist,” the notice reads.
That deceptively technical phrase points to a more intriguing operating domain: space.
Rads to Watts is a direct evolution of a Request for Information (RFI) DARPA issued in August 2024. The RFI posed an ambitious question: Could direct energy conversion from nuclear sources achieve the high-power, long-duration outputs required for next-generation missions?
Less than a year later, DARPA’s answer is a resounding yes.
From Theory to Action: “Rads to Watts” A High-Risk, High-Reward Bet on Radiovoltaics
Nuclear power has long been touted as the only viable option for sustaining operations in remote or extreme environments, whether on Earth, in orbiting spacecraft, or in future Moon and Mars habitats.
Systems, such as radioisotope thermoelectric generators (RTGs), have powered NASA missions for decades, including the Mars rovers and deep-space probes like Voyager. These devices rely on thermal conversion processes, in which energy from decaying isotopes or fission reactions heats a material, which powers turbines or thermoelectric systems.
However, these legacy methods are bulky and ill-suited for compact, remote applications. Moreover, they typically produce only a few hundred watts of power and degrade over time.
DARPA is now proposing to leapfrog that plateau by enabling “kilowatts” of electrical output through compact, solid-state devices that directly harvest energy from nuclear radiation.
“The ultimate vision of Rads to Watts is to enable radiovoltaics that convert high-power nuclear radiation into kilowatts of electrical energy,” the program notice states.
The goal is to create compact, high-output energy systems that require no moving parts, no fuel resupply, and minimal shielding—essential for operating in locations where “a logistics supply chain…does not exist.”
That last phrase, lifted straight from the program notice, is loaded with implications. It suggests DARPA is preparing for missions in environments like the Moon, Mars, or deep space—domains where resupply is not just expensive but physically impossible.
DARPA’s Growing Nuclear-Powered Ambitions
The Rads to Watts program didn’t emerge in a vacuum. In August 2024, DARPA issued a Request for Information (RFI) expressing the agency’s frustration with the glacial pace of innovation in nuclear power systems.
“Methods to convert the energy of nuclear fission reactions and the decay of radioisotopes into electricity have not evolved since the invention of radioisotope power systems (RPS) and fission reactors over 70 years ago and remain unoptimized,” the RFI reads.
DARPA specifically challenged researchers to rethink the problem at a fundamental level. Could the energy from nuclear emissions—alpha, beta, gamma, or neutron radiation—be captured and converted directly into electricity using solid-state materials? Could such systems generate tens or hundreds of kilowatts, operate for decades, and remain compact and efficient enough for operating in the “space domain.”
The August 2024 document called for responses that explored novel materials like radiation-hardened self-healing perovskites, bi-layer graphene, and doped semiconductors that generate power even from secondary radiation created within the device itself.
These questions are the foundation for DARPA’s new “Rads to Watts” program and the vision of developing high-power radiovoltaics that can endure extreme radiation environments without breaking down.
The Core Challenge: High Power, High Efficiency, Long Life
Radiovoltaics, or “atomic batteries,” are not new. They’ve powered microelectronics and niche applications for years—albeit at extremely low levels, often just nanowatts to milliwatts. The problem has never been the concept but the scalability.
Materials quickly degrade in high-fluence environments—where particles strike a device with incredible frequency and energy. Lattice defects accumulate in semiconductors, trap electrical charges, and degrade the bandgap needed to produce current. Efficiency plummets and the device dies long before its radioactive source is spent.
DARPA’s initial call for information directly addressed this, stating: “The lifespans of candidate semiconductor materials at high power are mostly limited by the ability to withstand excess radiation energy over time and maintain performance.“ The agency called for solutions that could operate for decades—on par with the half-lives of the nuclear materials themselves.
The August 2024 RFI cast a wide net, seeking academic, industrial, and governmental insight into whether such technologies were feasible and how they could be developed.
The notice encouraged speculative thinking around new materials, bandgap engineering, multijunction approaches, and smart shielding that could generate and manage radiation energy.
By contrast, with the announcement of Rads to Watts, DARPA is pivoting from exploration to execution. Program participants are called to abandon “typical low-power radiovoltaic architectures“ and develop entirely new classes of materials and device structures.
The emphasis is not just on initial efficiency but durability over time and exposure—technological qualities that, if achieved, could fundamentally change how humanity powers devices in space and other extreme domains.
Strategic Implications: “Rads to Watts” Powering the Moon, Mars, and Beyond
While the language in DARPA’s Rads to Watts program announcement remains measured and technical, the strategic potential is clear.
In space, power is not just essential—it’s existential. For instance, the two-week lunar night renders solar panels ineffective on the Moon. Battery storage becomes impractical at scale, and the cost of sending fuel from Earth is astronomical.
However, a compact nuclear radiovoltaic system that quietly produces kilowatts of electricity for years without intervention would revolutionize lunar operations. It could power autonomous construction bots, habitat life-support systems, or communications relays. On Mars, where sunlight is weaker, and dust storms can obscure solar panels for weeks, the advantages only multiply.
Additionally, permanent or semi-permanent orbital and lunar facilities powered by autonomous nuclear systems could grant the U.S. military and intelligence community unprecedented reach and resilience in space.
Moreover, space is increasingly becoming a contested domain, with China and Russia investing in lunar ambitions and space-based defense infrastructure. As terrestrial conflict threats evolve to include satellite disruption and orbital espionage, having persistent, untethered power in space becomes more than a technical challenge—it becomes a strategic necessity.
Radiovoltaics could also enable uncrewed probes to travel deeper into the solar system—or loiter in orbit for years—without needing solar or thermal systems that require maintenance or fail in extreme cold.
While NASA has ramped up its focus on nuclear thermal propulsion and fission-based surface power in recent years, Rads to Watts suggests a parallel push from the defense sector toward autonomous, long-endurance space infrastructure. This direction echoes earlier Department of Defense efforts—such as 2023 contracts issued by the U.S. Air Force Research Laboratory to develop nuclear-powered reactors for next-generation spacecraft.
By investing in radiovoltaics capable of kilowatt-scale output under extreme conditions, DARPA is laying the groundwork for energy independence in environments where national security and scientific exploration may increasingly converge.
The Path Ahead: From Lab to Launchpad
DARPA’s move from a request for information to a formal program announcement suggests the agency received promising responses to its 2024 call. Though the notice makes clear that “Rads to Watts“ is not yet a formal solicitation—and may never become one—the language is unmistakably forward-looking and suggests confidence in the technical path forward.
The notice invites research that challenges current assumptions, expands material science boundaries, and opens the door to entirely new categories of power systems.
It also signals DARPA’s increasing willingness to invest in enabling technologies that, while not explicitly military, have deep dual-use potential across space exploration, planetary science, and national defense.
The following steps will likely involve broad agency announcements (BAAs), proposers’ days, and the selection of research teams. DARPAConnect, the agency’s onboarding platform, is already encouraging new researchers to participate, hinting that DARPA wants to cast a wide net across academia, industry, and government labs.
Ultimately, what began as a theoretical inquiry into overcoming the limitations of legacy nuclear technology has become a tangible program to power the next frontier of human and robotic exploration.
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com