Nuclear Battery which might last for 433 Years

 NASA’s most ambitious Power source, a Nuclear Battery which could last 433 Years  

What if a space probe could run for over 400 years? NASA’s new nuclear battery might make that possible. Spacecraft have used a plutonium isotope to stay afloat for decades, but another isotope could last even longer. Radioisotope power systems (RPS) keep spacecraft going with nuclear batteries. Until now, RPS operated using a plutonium isotope, but researchers have found that an isotope of americium could keep spacecraft engines going even longer. A collaborative effort between NASA and the University of Leicester is now developing batteries with this isotope for future missions. Space, at least as far as we can fathom, is infinite. Rocket fuel is finite. While we haven’t yet found a way of keeping spacecraft from sputtering to a halt light-years away from Earth, NASA has the next best thing, and it’s radioactive.

The goal of NASA and the University of Leicester are to develop a new nuclear battery powered by americium-241, a radioactive isotope capable of fuelling space probes for 433 years. The research was recently featured and it could mark a major turning point in how we think about long-duration space missions. NASA has been using radioisotope power systems (RPS) which involve nuclear batteries since the early 1960s to power missions including both Voyagers, New Horizons, Curiosity, and, most recently, Perseverance. (The Dragonfly quadcopter meant to explore the methane lakes and seas of Saturn’s moon Titan will also rely on RPS.) Radioisotopes are unstable forms of elements which can only regain stability by degrading, and it is the breakdown of radioisotopes which generates heat and keeps the battery going. While that might sound futuristic enough, NASA is intending to level it up. The space agency has used plutonium-238, or plutonium oxide, as fuel for decades. The half-life of this isotope, how long it takes for an isotope’s radioactivity to drop to half its original level, is nearly 88 years. Now, however, the isotope americium-241 is being eyed for upcoming missions. With a half-life of almost 433 years, it lasts centuries longer than plutonium-238, and could keep spacecraft venturing far further into the unknown.

Radioisotopes need to meet NASA’s strict criteria to qualify for missions. For one, whatever form they take needs to be nontoxic (or minimally toxic) to the body, and they need to be insoluble so they are not easily absorbed by the body. As such, the fuel is usually in ceramic form, so instead of vaporizing and potentially being breathed in, they break into large fragments which cannot be absorbed even if ingested. For another, spacecraft instruments also need to be kept safe, so any radioisotopes used in a battery must have a sufficiently long half-life, remain stable at high temperatures, and only need a small amount to generate a blast of heat. This allows them to keep obiters, rovers and space telescopes going for decades. Radioisotope power systems (RPS) generate electricity from the heat released by radioactive decay, and they’re a big reason missions like Voyager, New Horizons, Curiosity, and Perseverance have lasted so long. Until now, these batteries relied on plutonium-238, which breaks down steadily over time but can only power missions for a few decades at best. Americium-241 changes that. With a half-life of 433 years, it keeps producing heat for centuries. This opens the door to truly long-term missions, ones that could outlast not just the spacecraft’s designers but entire generations of scientists. And yes, NASA has strict safety standards for anything radioactive. Americium-241 passes the test. It’s “minimally toxic,” and when used in ceramic form, it won’t vaporize. If something goes wrong, it breaks into large, chunky pieces, meaning it’s a lot less likely to be inhaled or absorbed into the body. 

Until now, only plutonium-238 has been able to pass. But this past January, NASA’s Glenn Research Centre (Glenn) and the University of Leicester in the UK joined forces and agreed to test-drive americium-241. They are also looking into using an optimal method of generating electricity from this radioactive fuel, instead of a system that can only power up a spacecraft using a crankshaft, a free-piston Stirling convertor allows pistons to float within the engine in microgravity (NASA has been using them for years). In 2020, a convertor at NASA’s Glenn Research Centre which was running on RPS reached 14 years of maintenance-free operation, which just so happens to be the minimum life needed for many deep space missions. Wayne Wong, head of Glenn’s Thermal Energy Conversion Branch, described the progress as “particularly significant” for missions which have long cruise times and can’t afford any downtime. “Previous flight projects determined that the mission duration requirement for RPS is 14 years, particularly for outer planetary missions with long cruise times.” Plutonium-238 had been on a 30-year production hiatus before 2011, when NASA received government funding to support the Department of Energy’s Office of Nuclear Energy to restart production for space missions. The isotope is currently produced at Oak Ridge National Laboratory (ORNL), the Idaho National Laboratory (INL) and several other facilities. The production process for americium-241 is currently undergoing improvements for efficiency and safety at Los Alamos National Laboratory.

One of the challenges with plutonium-238 is that it’s expensive and slow to make. In contrast, americium-241 is much easier to get. It’s a common by-product of nuclear reactors, so there’s already a decent supply. Right now, Los Alamos National Laboratory is working on improving the production process, making it safer and more efficient for long-term use in space. There are some challenges. Americium-241 emits more gamma radiation than plutonium, which means better shielding will be needed. But engineers seem confident that’s a solvable problem, especially considering how much longer this fuel can last. This tech isn’t just about extending mission timelines. It’s about changing how we think about space travel entirely. A probe launched in 2050 could, in theory, still be functioning in the year 2480. That’s not science fiction anymore, it’s a real possibility. Missions like Dragonfly, a nuclear-powered drone heading to Saturn’s moon Titan, are already banking on long-lasting battery tech. If americium-241 proves viable, it could fuel the next generation of deep space explorers, ones designed to operate for hundreds of years without stopping. Meanwhile, the Voyagers keep heading further and further from the Solar System, still powered by RPS, leading the way for missions to come. And as the Voyager spacecraft powered by the fading warmth of old-school RPS, NASA’s new battery tech is getting ready to take over, lighting the path for everything that comes next in world around us.