The European Space Agency (ESA) has announced that its upcoming Mars mission will feature a new nuclear-powered device that uses the radioactive decay of americium. This marks the first time such a device will be used in a spacecraft, signifying a significant step towards ESA’s goal of reducing its dependence on other space agencies for power systems in future missions to other planets.
Europe’s first Mars rover, Rosalind Franklin, has faced numerous delays due to technical issues, the COVID-19 pandemic, and the cancellation of ESA’s partnership with the Russian space agency Roscosmos following Russia’s invasion of Ukraine. To proceed without Roscosmos, ESA has developed new capabilities and partnered with NASA to fill the remaining gaps in the mission plan.
The EuropeaN Devices Using Radioisotope Energy (ENDURE) project, aims to provide ESA with its own Radioisotope Power System (RPS) capability. This will enable the agency to power future missions to other planets without relying on external partners. Another deliverable of ENDURE is a device that harnesses the heat produced by the decay of radioactive elements. While a Radioisotope Heater Units (RHU) uses the heat naturally produced by radioactive decay, a nuclear battery — known as a radioisotope thermoelectric generator — converts that heat into electrical power.
RHUs have been used in previous missions, but ESA’s RHU is not only a first for Europe but also the first to use americium-241, a by-product of plutonium decay. Although americium-241 has a lower power output per gram compared to plutonium-238, it is more abundant and cost-effective, potentially making the americium RHUs less expensive overall.
As the power source contain radioactive materials, they require certification before launch to ensure planetary protection and adhere to launch-safety requirements. ESA has submitted a paper on Implementation of the guidelines from the international safety framework for nuclear power source applications in outer space to the Committee on the Peaceful Uses of Outer Space (COPUOS). The team at the University of Leicester, leading the development, is working diligently to fulfill these requirements in time for the planned 2028 launch.