NASA has long relied on radioisotope power systems (RPS) to power its most ambitious missions, from the Voyager probes to the Curiosity and Perseverance rovers. These nuclear batteries convert the heat generated by decaying radioactive isotopes into electricity, ensuring that spacecraft continue operating far beyond the reach of solar power. Now, NASA is testing a revolutionary new fuel source—americium-241—which could keep spacecraft running for more than four centuries.
From Plutonium to Americium: A Leap in Longevity
For decades, NASA used plutonium-238, an isotope with a half-life of nearly 88 years. While sufficient for multi-decade missions, plutonium has its limits. By contrast, americium-241 boasts a half-life of 433 years, opening possibilities for missions lasting centuries rather than decades. This longer lifespan means spacecraft could travel farther into deep space, conduct extended planetary exploration, and power scientific instruments for generations.
Safety and Engineering Challenges
Radioisotopes must meet strict NASA safety standards. They need to remain stable at high temperatures, resist toxic exposure, and avoid dissolving into the human body if accidents occur. To achieve this, fuels are often sealed in ceramics, which shatter into large, non-absorbable fragments instead of vaporizing. This makes them far safer for both launch environments and long-duration space missions. Americium-241 not only satisfies these requirements but also demands smaller quantities to generate sufficient power, increasing its efficiency.
The Stirling Converter Advantage
One of the most promising technologies being paired with americium is the free-piston Stirling converter. Unlike traditional systems that rely on moving mechanical parts like crankshafts, this converter allows pistons to “float” inside the engine in microgravity. This reduces wear, enhances durability, and ensures continuous power generation. In fact, a Stirling converter tested at NASA’s Glenn Research Center has already run for 14 years without failure, proving its long-term reliability.
International Collaboration for Space Power
Earlier this year, NASA’s Glenn Research Center partnered with the University of Leicester in the UK to refine americium-241 fuel systems. At the same time, institutions such as Oak Ridge National Laboratory (ORNL) and Los Alamos National Laboratory are working to improve the production efficiency and safety of this isotope. With these efforts, NASA is preparing for a new era where spacecraft won’t just last for decades—they could potentially remain functional for centuries.
Conclusion
The development of americium-powered nuclear batteries marks a game-changing leap for space exploration. With a lifespan of 433 years, this technology could redefine how humanity explores the solar system and beyond. From orbiters and landers to telescopes positioned at the farthest reaches of space, americium could ensure that NASA’s most daring missions never run out of power. As the space age evolves, long-lasting nuclear energy may become the backbone of interstellar exploration.
