As the race to explore the far reaches of our solar system intensifies, NASA is venturing into a new frontier not just in space, but in how we power our journeys there. The agency’s latest breakthrough revolves around an alternative nuclear fuel, americium-241, which could replace the long-relied-on plutonium-238. The promise? A power source that’s cheaper, longer-lasting, and capable of withstanding the harsh realities of deep space, revolutionizing both robotic and human missions to destinations where sunlight is weak or non-existent.
Earlier this year, NASA’s Glenn Research Center in Cleveland teamed up with the University of Leicester in the UK to put this idea into practice. Their joint effort focused on testing a Stirling generator powered by simulators that replicate the heat output of americium-241. These tests are designed to mimic real-world performance without exposing researchers to radioactive materials.
Unlike traditional heat engines, the Stirling convertor has no crankshaft or rotating bearings. Instead, it uses floating pistons, allowing for continuous operation with minimal mechanical wear over decades. The system is built with redundancy in mind, continuing to produce power even if one unit fails — a non-negotiable feature for missions that travel far beyond Earth’s reach.
Salvatore Oriti, a mechanical engineer at NASA Glenn, emphasized how quickly the project moved from concept to functional prototype. That rapid progress, he said, was made possible by the strong collaboration with international experts. Early efficiency and performance results were so promising that the team is now developing a next-generation prototype, designed to be lighter, more efficient, and able to endure environmental stress testing including vibration, extreme temperatures, and vacuum conditions, all critical for space travel.
Why americium-241? Aside from its extraordinary 432-year half-life, making it ideal for long missions, it’s more readily available and cost-effective than plutonium-238. These advantages are key as demand grows for power systems that can support not just interplanetary probes, but future crewed missions and lunar surface operations especially in areas like the Moon’s shadowed craters or the distant, icy moons orbiting Jupiter and Saturn, where solar energy is insufficient.
NASA’s interest in americium builds on years of research led by the European Space Agency, which also explored the isotope’s space applications. Now, with new momentum from NASA, the concept is gaining tangible form, a generator that could one day power landers, surface habitats, and science instruments for decades with minimal maintenance.