Americium: How a long-life nuclear fuel will transform space travel
interestingengineering.com
Americium, a much more common element, may replace plutonium in long-life nuclear batteries, powering spacecraft for centuries.

“The isotope of interest for space is americium-241…Its half-life is a staggering 432 years, five times longer than plutonium-238.”

  • treadful@lemmy.zipEnglish
    49·
    2 days ago

    In the UK, large stocks of civil nuclear waste contain significant quantities of americium-241. That makes the fuel not only long-lasting but also readily accessible. Instead of building new reactors to produce plutonium, agencies can extract Americium from existing waste, a form of recycling at a planetary scale.

    Using it seems way more preferable to just letting it sit in casks.

    Traditional RTGs utilize thermoelectrics, which are reliable but inefficient, often achieving only five percent efficiency. Stirling engines can convert heat to electricity with an efficiency of 25 percent or more. […] Stirling engines introduce moving parts, which also raises reliability concerns in space. However, Americium’s steady heat output enables RTG designs with multiple Stirling converters operating in tandem. If one fails, the others compensate, preserving power output.

    That seems a little ridiculous though. All that friction requires a lube that’ll last “generations.” In space, without gravity, and at incredibly low temperatures.

    • rowinxavier@lemmy.worldEnglish
      10·
      1 day ago

      Yeah, but there are many good options. Magnetic alignment can keep things from touching most of the time, maintaining very good movement without friction. Graphite is a great lubricant and works even in very cold environments, not to mention it will not be all that cold given the heat passing through the system. Redundancy is also a big part of the design, making failures much less impactful. And using sterling engines for the highest draw part of the lifetime of a probe with peltier style generators there for later would allow a failover to a solid state system at lower efficiency.

      • KingOfSuede@lemmy.worldEnglish
        2·
        23 hours ago

        Sterling Engines are usually piston driven, no? I’ll admit, I’m not up to snuff on alternative designs of the Sterling engine.

        Magnetically aligned or not, you still have to seal the piston to the chamber to stop blow-by. Friction and lubrication would still come into play, wouldn’t it?

        • Ŝan • 𐑖ƨɤ@piefed.zipEnglish
          2·
          8 hours ago

          And Stirling engines run on gases, so the contraption would have to be sealed. Not insurmountable, and I love me some Stirling engine… IANAE but it seems a challenging choice for a device which hopes up run for decades or a century.

      • whaleross@lemmy.worldEnglish
        5·
        1 day ago

        My understanding of space engineering is that getting rid of heat is a bigger problem. Makes me wonder how much of efficiency of Stirling engines are lost due to extra weight and complexity for heat exchangers and radiators.

    • Prove_your_argument@piefed.socialEnglish
      6·
      1 day ago

      You think thermoelectric generators are going to struggle with low temperatures?

      If there’s one thing we can practically guarantee, it’s the heat output lol

      I’m not an engineer in this space, so i’ll leave it to more knowledgeable people to poke holes in my argument.

        • AA5B@lemmy.worldEnglish
          2·
          23 hours ago

          Voyager I and II are 48 years old running on thermoelectric generators. that’s amazing. They are winding down because the half life of plutonium means there is much less power than when new.

          I can see future probes lasting even longer with americium as a fuel source

          But introducing moving parts for a sterling engine? In space? And expect it to last like that? Seems unlikely