Space Nuclear Power for Moon and Deep-Space Missions: Americium-241 Pellets, RHUs, and Perpetual Atomics

Overview

Nature investigates a novel approach to space power that turns nuclear waste byproducts into high-density fuel pellets for spacecraft. The UK spin-out Perpetual Atomics is developing americium-241 based technology to generate heat and electricity in space where solar power is limited, such as shadowed lunar craters and deep-space missions.

• proprietary pellet recipe aims for stability and scalability
• surrogates used to test non-radioactive versions of the chemistry
• first solid americium-241 pellets for spaceflight demonstrated
• RHU and thermoelectric modules connect heat to usable power

Introduction

Nature profiles a space power program that seeks to reuse nuclear byproducts from Earth to power future missions. The focus is americium-241, a decay heat source that could complement solar panels, especially where light is scarce or unavailable. The UK spin-out Perpetual Atomics is advancing a scalable fuel pellet recipe and aims to deliver compact, reliable heat and electricity for space environments.

Background

Americium-241 accumulates as plutonium-241 decays, and its steady heat output makes it an attractive energy source for space. The challenge has been turning this waste byproduct into a stable, solid fuel form suitable for spacecraft. The team has worked to overcome crystal-structure changes that typically cause cracking, introducing additives and a testing workflow that uses non-radioactive surrogates to iterate recipes without handling radioactive material.

Technical Approach

The core effort has produced a stable, scalable fuel form and begun translating the recipe into a genuine nuclear environment with U.S. partners. Containment is multi-layered: a welded platinum rhodium clad enclosure protects the fuel from accidental release and mechanical shocks, while a carbon-carbon composite structure forms the thermal protection system. The system is encapsulated as a radioisotope heater unit, RHU, capable of surviving launch hazards and re-entry heating loads via ablation of the carbon-based shield.

Missions and Applications

One of the first missions to leverage this heater is on the Rosalind Franklin Mars rover, where the RHU on the landing platform helps keep systems warm and extend battery life during pre-deployment checks. The technology is also positioned for terrestrial uses such as deep ocean power where continuous energy is needed without long cables. The team envisions space power becoming a utility in orbit and on planetary surfaces, enabling more routine exploration and science.

Power Conversion and Future Systems

Heat can be converted to electricity with thermoelectric modules that achieve roughly 5 percent efficiency, producing about 10 watts of electricity from hundreds of watts of heat for a larger assembly, while the majority of heat can be managed or dumped as waste heat. A more advanced engine-based generator is in development to turn heat into motion and electricity, a design aimed at robustness since losing a single engine would not collapse overall power output.

Outlook

Beyond Mars and the Moon, space power systems based on americium-241 could underpin deeper exploration and long-term habitats, reducing reliance on solar power and enabling operations through long lunar nights and shadowed regions. The broader goal is to build space infrastructure in a manner analogous to a utility company powering life-supporting activities across space, linking science, exploration, and technology in a scalable, trusted framework.