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NASA Power Space Hardware

New Small Fission Reactor For Deep-space Missions Demonstrated 122

cylonlover writes "Exploring the regions of deep space beyond Mars means sending probes where solar power isn't practical. Since the 1960s, NASA has equipped its Apollo missions and unmanned explorers with Radioisotope Thermal Generators (RTGs). These have worked very well, but they run on plutonium 238, which is currently in short supply. Therefore, the Los Alamos National Laboratory is developing a new small nuclear reactor for spacecraft that uses uranium instead of plutonium to power Stirling engines and generate electricity. At the Nevada National Security Site's Device Assembly Facility near Las Vegas, engineers from Los Alamos, the NASA Glenn Research Center and National Security Technologies LLC conducted a Demonstration Using Flattop Fissions (DUFF) experiment that produced 24 watts of electricity using a pair of free-piston Stirling engines."
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New Small Fission Reactor For Deep-space Missions Demonstrated

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  • I found it odd that this little blip state that Plutonium is in short supply. The reason we don't have a lot of it is because the US is actively destroying it's Plutonium reserves. There are countless patents for machines that destroy Plutonium. Here is an article about how the DOE is considering alternatives to destroying Plutonium, like using it for something constructive instead of making bombs. []
    • Re: (Score:2, Informative)

      by Anonymous Coward

      The usual plutonium bomb/reactor fuel is Pu 239, which is not exactly common (consider how hard Iran tries to get its hands on some). Pu 238 is much rarer than Pu 239, because of its short half life (87.7 years compared to 1000's of years). That higher radioactivity is also why it's usable in an RTG (thing that generates power by the heat of radioactive decay). With a fission reactor they could use Pu 239 which is (to nuclear countries like the US) plentiful, relative to small uses like this.

    • Re: (Score:2, Informative)

      by Anonymous Coward

      It is truly an irrational pursuit that only sees these materials as weapons. It is our most valuable resource. Actually that would be U-235. We could be using it a lot more efficiently in a new generation of molten salt type reactors.

      • by rubycodez ( 864176 ) on Friday November 30, 2012 @12:42AM (#42138721)

        even depleted u-238 can be used in the right type of reactor, and thorium too. we have millenia of fission fuel supply, we just need to start using smart designs rather than the primative and dangerous gen i and ii

      • It is truly an irrational pursuit that only sees these materials as weapons. It is our most valuable resource. Actually that would be U-235. We could be using it a lot more efficiently in a new generation of molten salt type reactors.

        When will all the pro-nuke dorks on this site get it through their heads that the problem with fission power is NOT TECHNICAL. And that therefore, no newfangled fission technology will accomplish anything.

        The problem with fission power is human nature. If this species were competent enough to obtain the majority of its power from nuclear fission, we wouldn't be drawing up war plans right now over Iran's nuclear "power" program.

    • > I found it odd that this little blip state that Plutonium is in short supply.

      Plutonium 239, used in weapons, isn't in short supply. Plutonium 238, used in RTGs, is.

  • by Anonymous Coward

    Am I the only one thinking of beef/simpsons when I read this?

    One of the things about RTG []s is that compared to SRG []s, it has no moving parts.
    It has been developed for some time and has been proven to be very reliable.
    They can always look at other non-Plutonium isotopes for RTGs such as Americium-241 [] which has a significantly longer life-span (Am-241's half-life is 432 years while Pu-238 is 87.7)
    It also looks like there are some organizations working on a more advanced STG []

    Too bad the article doesn't go into de

  • by Anonymous Coward

    We are moving from a heat driven passive reactor to a heat driven mechanical generator... seems like step back and a new point of failure for modern space vehicles...

    • by Genda ( 560240 )

      Nah, the younger engineers are just infatuated with steam-punk... Wait till you see the generation of satellites with the brass fittings... woohoo!,/p>

    • by funkboy ( 71672 )

      We are moving from a heat driven passive reactor to a heat driven mechanical generator... seems like step back and a new point of failure for modern space vehicles...

      Stirling Engines are actually quite reliable. They're often used on things like waste heat recovery systems to power remote oil & gas installations, where they have to run for extended periods in nasty environments.

      The main limitation to more popular use of Stirling-cycle engines vs. the ICE is that they need an external source of motion to get them going (well, ICEs do too), and they take a while to "warm up" before they reach operational efficiency. Ford messed with them for a while in the 70's when

      • Would be perfect for an advanced hybrid vehicle using all-electric drive. The combustion engine is there just to keep the battery pack charged, a 30 second warm-up (for a 3 minute warm-up for that matter) would be fine.

  • When do we get them? (Score:2, Interesting)

    by evilviper ( 135110 )

    When do we get them? Electric cars are all the rage... Imagine you had a non-stop range extender! Imagine your car just charges itself when parked anywhere. Better yet, imagine an RV powered by one of these... park out in the middle of nowhere, and still have a decent amount of power. Or in some cases where communities are isolated, how about end-of-the-block SRGs? The best thing about an EV/RV SRG is that the half-life is about 80 years, so just one will last you a couple lifetimes.

    A number of years

    • by dbIII ( 701233 )

      Better yet, imagine an RV powered by one of these

      Hmm, 24 Watts.
      Yep, I can imagine it, an RV up on blocks in a yard and not going anwhere :)

      There's a bit of an awkward gap between little Stirling engines and a honking great big reactor that can move a submarine. I'm not sure if there's anything in that gap - anyone out there with some ideas?

      • by funkboy ( 71672 )

        Hmm, 24 Watts.


        “The nuclear characteristics and thermal power level of the experiment are remarkably similar to our space reactor flight concept,” said Los Alamos engineer David Poston. “The biggest difference between DUFF and a possible flight system is that the Stirling input temperature would need to be hotter to attain the required efficiency and power output needed for space missions.”

        Though successful, the Stirling engine system used in the experiment isn't considered enough for practical purposes. For missions beyond Jupiter, much more power is needed. “The heat pipe and Stirling engine used in this test are meant to represent one module that could be used in a space system,” said Marc Gibson of NASA Glenn. “A flight system might use several modules to produce approximately one kilowatt of electricity.”

        With the right hardware I could build a nice little server farm that runs on a kilowatt... Or even better give me a flywheel that I can charge with the excess mechanical energy generated during off-peak periods and tap during peaks, and double the peak load of the system.

        • by dbIII ( 701233 )
          That's getting a bit of a way from an RV and answering a completely different question to the one asked.
    • by Hentes ( 2461350 )

      Giving radioactive materials to the general populace can be dangerous. There are bad people out there.

      • True, but there are way more stupid people out there than bad people so...

        Hmm, I guess I need to think a bit more about my counter argument. Let me get back to you.

      • Giving radioactive materials to the general populace can be dangerous.

        Outlaw smoke detectors!

        I'm sure most radioactive materials are less dangerous than, say, fertilizer or gasoline.

    • I thought about this too. You could have community based reactors but then it also occurred to me that you'd also have a ready source of catastrophe every few thousand feet. Knowing the electrical provider in my area, I know it's a disaster just waiting to happen.

      Between utility poles and manhole covers with voltages on them to theft of manhole covers it's getting interesting.

      In case you're wondering, it's National Grid.
    • When the governments of the world decide it's ok for civilians to own weapon's grade uranium.

      TFA mentions that the reactor uses a 50 lb, which is about half the critical mass of uranium 235. In order for the core to maintain a fission reaction, even with the neutron shield in place, it's probably going to use weapons grade uranium.

      There's been a pretty big effort to cut down on civilian usage of weapon's grade uranium(IE research reactors) and other fun fissile substances for fear of people making b

    • I'm sure that in 1985, plutonium is available in every corner drugstore, but in 2011, it's a little hard to come by.

    • Yeah, so that way when you get a 100-car pileup on a Texas freeway, instead of just having the chemical danger of automotive fluids and lubricants, you also get a nice Nuclear Emergency Response Team showing up and scrubbing everyone down!

      • NASA's RTGs are damn near indestructible! They fall from orbit without breaking open.

        • Yeah, but we're not talking about RTGs. RTGs are a lump of Pu-238 with a thermocouple and really couldn't be simpler. TFA is talking about a miniaturized reactor, with a criticality inside, and a mechanical control system that can bend / break / wear out.

  • It's small (Score:4, Informative)

    by Animats ( 122034 ) on Friday November 30, 2012 @04:26AM (#42139431) Homepage

    Nuclear reactors have been used in space since the 1960s, by both the US and USSR. They've generally powered thermocouple-type electrical generators, which are inefficient but very reliable. The one US reactor launched massed 290Kg and produced 500 watts. Soviet reactors were bigger and produced more power.

    The innovation here is a small unit around 65Kg that produces only 24 watts. Electronics has become so low-power that a 24 watt power plant is useful.

    Note that all these reactors are unshielded.

    • Are you conflating RTGs and reactors? I associate thermocouples with RTGs, not reactors, and a cursory wikipedia search didn't find any reactors using thermocouples.

      RTGs rely on the natural decay of the radioactive fuel, whereas reactors use a chain reaction to accelerate the decay of the fuel. Voyager etc. use RTGs with thermocouples. The device here is an actual reactor, with a control rod and neutron reflector. I'm aware that the U.S.S.R. built reactors for space. Wikipedia lists a few NASA reactor proje

      • by Animats ( 122034 )

        Are you conflating RTGs and reactors? I associate thermocouples with RTGs, not reactors, and a cursory wikipedia search didn't find any reactors using thermocouples.

        No, I'm not The US launched one reactor [], and it used a thermocouple-type generator. The USSR launched many radar satellites with reactors in the 1KW to 5KW electrical output range. One crashed into Canada.

  • by Anonymous Coward

    Why contaminate the rest of the Universe? We have ruined our own planet and now we're going to ruin someone else's.

    They should only allow green energy in space - solar, or hydro, or wind turbines. Wind turbines would work fine on Mars...

    • by stiggle ( 649614 )

      Quick - shut down that large unshielded nuclear furnace in the sky!
      Oh yeah, thats the sun.

      Properly used - nuclear is a very green energy and no greenhouse gasses or climate change to worry about.
      You need something to provide a constant baseload for the times when the sun don't shine and the wind don't blow.

  • by argStyopa ( 232550 ) on Friday November 30, 2012 @07:46AM (#42140229) Journal

    IANARS, but it seems to me that while this is a great idea, there's a weak point in the mechanical linkages and the stirling engine.

    RTGs use thermocouples which, while never very efficient, have the advantage of being solid state - a huge reliability benefit.

    If you have this sort of system powering deep-space probes (or hell, near-space systems) I'd think that aside from all the normal wear-and-tear issues of any linkage (lubrication, debris, even erosion over time) would be exacerbated by the thermal extremes in space. Further, the vibration created through the rest of the craft couldn't be helpful for the lifespan of the other components. Finally, for the sorts of precision needed for space operations (pointing a space telescope comes to mind) the constant oscillation of mass within the craft probably would make other things significantly more difficult.

    Again, not a rocket scientist, but from my point of view as 'cool' as this is, and as useful as it may be, it doesn't seem like something very applicable to space operations.

    Tinfoil hat bit:
    Now...if one needed a long-term power source for something much less precise like earthly drone operations... (I don't know the mass/power here at all)...

    • by hpa ( 7948 )
      The use of Stirling engines has already been planned for future RTG missions, this is just a change of heat source.
  • Put one of these in my backyard and let me plug in. There, now you have it, I'm willing to go green (nuclear green) for my electricity.
  • One thing that is not really covered is that launching a reactor (unlike *operating* a reactor in *low-earth orbit* like the Soviets did) is that it is substantially safer than launching an RTG. An RTG is at its maximum activity at the point of launch, and in the case of a low altitude launch failure could spread measurable radiation over an area. In contrast, the reactor isn't (shouldn't be) activated until already on an earth escape trajectory. "Virgin" (never irradiated) U-235 is not very radioactive:
  • ...the Pu-238 contained within USA's existing U-233 stockpile is being destroyed along with it. []

    Also, the U-233 could serve as a "nuclear catalyst" in Molten Salt Reactors fed Thorium as fuel. Such reactors could produce Pu-238 in an easily partition-able form since they would be in a liquid state, and there would be no unwanted isotopes to contaminate the plutonium. (Isotopes being harder to separate than other elements.)

    If you live in the USA please conside
  • The difference between this approach and, for instance, the radioisotope thermoelectric generator that is *still* powering two Voyager spacecraft after 35 years, is the inclusion of parts that must move repeatedly to generate electricity. Is this really a good idea?

    • Yes. The thermocouples powering voyager (the T part of RTG) are degrading, and currently only producing about half their original output. A stirling engine can be made very reliable, more so than a thermocouble.
      • Right, but there's different kinds of reliable. For instance, there is mean time between failure, and expected lifespan. A mechanism can be less likely to fail at any given moment, but still have a shorter useful lifespan. Motion implies friction, and requires something to reduce same, whether it be a coating or an actual lubricant (which is unlikely in this case considering the environment). Bearings do wear out over time.

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