A new americium-based power source could fuel the future of interplanetary exploration. Japan is developing a nuclear battery capable of lasting over a century in a groundbreaking move that could redefine how we power deep-space missions. Led by the Japan Atomic Energy Agency (JAEA), this compact energy source converts decay heat from americium, a byproduct of spent nuclear fuel, into electricity, offering a long-term alternative to solar panels for space probes traveling far from the Sun.
No Sun? No Problem.
While solar power has long been the standard for satellites and space probes, it quickly becomes ineffective in the shadows, whether on the dark side of the Moon, beneath thick planetary clouds, or beyond the reach of sunlight in the outer solar system. That’s where this new nuclear battery steps in.
Developed in collaboration with the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Advanced Industrial Science and Technology (AIST), this next-generation power source is expected to make its debut as a prototype by 2029. If successful, it could support long-duration missions to distant asteroids, icy moons, or other hard-to-reach frontiers where traditional power systems fall short.
A Radioactive Innovation
Instead of plutonium—the go-to isotope used in NASA’s radioisotope thermoelectric generators (RTGs) since the 1960s—Japan’s team has turned to americium, which forms when plutonium decays inside spent nuclear fuel.
Why americium? Japan has strict legal restrictions on the handling and transport of plutonium. Despite generating slightly less decay heat, americium sidesteps these constraints and still offers enough thermal energy to support essential spacecraft systems like communications and sensors.
Masahide Takano, senior researcher at JAEA’s Nuclear Transformation and Radiation (NXR) Development Center, says the battery could “provide almost permanent power for space probes,” unlocking long-term functionality in some of the most remote locations in our solar system.
Safety and Supply
Americium isn’t just theoretically feasible—Japan has already figured out how to harvest and safely package it. By isolating the element from uranium-plutonium mixed oxide (MOX) fuel, the JAEA can form americium into stable pellets encased in metal pins. This encapsulation method prevents leakage or contamination, even in the event of a rocket explosion during launch.
This focus on safety and sustainability is key to building trust in radioactive-powered systems, especially for missions that may fly over populated areas during launch or reentry.
Proof of Concept Already Glows
The JAEA has already demonstrated that americium can reliably generate electricity. In early lab tests, the team powered LED lights using a semiconductor system driven by americium’s decay heat. This is a small but crucial proof-of-concept showing that this technology is not only viable but already working.
Looking Ahead
With the prototype expected by 2029, Japan is laying the groundwork for a future where deep space missions are no longer limited by sunlight. The battery is being engineered to withstand the extreme vacuum, temperature swings, and radiation of space—an essential feature for any off-world mission.
As international interest in lunar bases, asteroid mining, and Mars colonization grows, long-lasting, compact power sources like these could become the cornerstone of next-gen space infrastructure.
