Americium batteries use americium-241—a byproduct of nuclear fuel reprocessing—as a radioisotope thermoelectric generator (RTG) fuel. Americium has a half-life of 432 years, far longer than plutonium-238, potentially enabling multi-decade missions. The UK Space Agency and European Space Agency are developing americium-based RTGs for deep-space and lunar missions. Working prototypes are estimated 5–10 years from deployment (as of 2019). Applications include spacecraft power for missions beyond solar panel viability and long-duration landers or rovers.
Deep-space missions require power where solar is inadequate. Plutonium-238 RTGs have powered Voyager, Curiosity, and Perseverance; plutonium supply is constrained. Americium offers an alternative fuel with longer half-life and UK/European production capability. Challenges include thermoelectric conversion efficiency, safety and licensing, and cost. Americium batteries represent a long-term option for space power; commercialization is limited to space applications.