back to article USA seeks Moon and Mars nuke power plant designs ready to fly in 2027

The US Department of Energy has published an RFI for a lunar nuclear power plant. The RFI specifies a “Fission Surface Power” unit “providing uninterrupted electricity output of not less than 10 kilowatts at the interface end of a 1-kilometer cable. The FSP system should provide 120 V (direct current) at the user interface of …

  1. DS999

    What are they going to do with the heat?

    Nuclear reactors require shedding a lot of heat, which doesn't work terribly efficiently in a vacuum. Better locate it near a big deposit of ice, that way it can use the excess heat to melt it for fresh water and maybe boil it for tea or something.

    1. Yet Another Anonymous coward Silver badge

      Re: What are they going to do with the heat?

      Space is 1, big and 2, cold so radiating heat isn't too difficult.

      And 10 kw isn't such a lot of power - about the same as a 100 people on a sofa

      1. Inventor of the Marmite Laser Silver badge

        Re: What are they going to do with the heat?

        100 people on a sofa? That's one heck of a group cuddle

        1. jake Silver badge

          Re: What are they going to do with the heat?

          Around here, good luck making space between the whippets & greyhounds ...

        2. David Lewis 2
          Coat

          Re: What are they going to do with the heat?

          No, at 2 metre Social Distancing restrictions, that is a BIG sofa!

      2. MyffyW Silver badge

        Re: What are they going to do with the heat?

        I don't disagree that space is indeed big. And it is also cold (when not bathing in radiation from a rather large fusion source 93 millions miles away). But getting rid of heat by electromagnetic radiation alone is not trivial. Good luck to potential applicants.

      3. Michael Habel Silver badge
        FAIL

        Re: What are they going to do with the heat?

        Excpept ypu forgot that Heat doesn't radiate well in the vacuum of Space. Why do you think that it takes tens of billions of years for a Red Drwarf to cool into a Black Dwarf? Because there is no effcient means of radiating all that heat away in the deep vaccum of space.

        1. spider from mars
          Boffin

          Re: What are they going to do with the heat?

          You're not wrong, but radiators in space are a pretty well-understood technology. Many satellites have them, as does the ISS. They just need to be sufficiently big, is all.

          Trivia fact: the ship from 2001 has originally designed to have realistically sized cooling radiators, but they removed them because they worried that the audience might think they were wings.

          1. Dave 126 Silver badge

            Re: What are they going to do with the heat?

            > Trivia fact: the ship from 2001 has originally designed to have realistically sized cooling radiators, but they removed them because they worried that the audience might think they were wings.

            I didn't know that, but it sounds right. Similarly, Clarke and Kubrick agreed that HAL's CPU would be the size of a shoebox, but Kubrick decided to make it room-sized so as to meet audience expectations - and HAL's CPU room providing the setting for a great scene.

        2. Cuddles Silver badge

          Re: What are they going to do with the heat?

          "Excpept ypu forgot that Heat doesn't radiate well in the vacuum of Space."

          Heat radiates very well in the vacuum of space. What it doesn't do is conduct or convect, which are generally much faster ways to remove heat. It's losing those two that causes problems for cooling, not any problem with radiation.

          1. Yet Another Anonymous coward Silver badge

            Re: What are they going to do with the heat?

            Back of the fag(*)-packet calculation

            10Kw/m^2 into space at near enough 0K implies a hot surface temperature of about 350C

            So as long as you can keep your reactor about the size and temperature of a pizza oven you are ok just sitting there. Make it any bigger or hotter and it gets easier.

            * term carefully chosen to trigger colonial commoners

            1. Charlie van Becelaere

              Re: What are they going to do with the heat?

              "Back of the fag(*)-packet calculation"

              Is there really any space to write out any calculations there? I should think they're filled with warnings and notices of enhanced flavour and whatnot.

              1. cbars Silver badge

                Re: What are they going to do with the heat?

                *inside of the back

        3. David Nash

          Re: What are they going to do with the heat?

          Radiation is radiation. There's no "inefficient" way of radiating. You might be thinking of convection.

        4. cbars Silver badge

          Re: What are they going to do with the heat?

          @Michael, others have already corrected you, but in case you're still confused on your example:

          "...Red Drwarf to cool into a Black Dwarf...?"

          Its the same reason polar bears don't look like cheetas: surface area to mass ratio. Big things lose heat slower, because they can only lose heat from their surface (by radiation in the case of stars, by convection and conduction too for fluffy animals). Stars are #massive

      4. The First Dave Silver badge

        Re: What are they going to do with the heat?

        Sorry, but the real problem is they are only asking for 120v, when we all know that you need 240v (RMS) for any real work.

        1. Martin Gregorie Silver badge

          Re: What are they going to do with the heat?

          Current is an issue too: if they're going to run 10 Kw - thats 83 amps at 120v DC - through 1km of cable, the cable will weigh about as much as the shielded nuke. If it doesn't, then they may put 10Kw in but they aren't going to get anything like that out of the other end.

          120v AC would make much more sense because the cable could be a lot thinner and the weight savings would almost certainly be much more than the weight of a DC->AC converter at the nuke and rectifiers at the far end.

          1. Wellyboot Silver badge

            Re: What are they going to do with the heat?

            More likely it'll be a couple of thousand vAC going down a thin set of wires at a low ampage, someone will be doing a very detailed all up weight calculation.

          2. Bronek Kozicki Silver badge

            Re: What are they going to do with the heat?

            Perhaps 1km long superconducting cable on Moon is easier to build than on Earth?

          3. Killing Time

            Re: What are they going to do with the heat?

            'the cable will weigh about as much as the shielded nuke'

            How did you arrive at that guesstimate? What about an aluminium conductor?

            By the way, 120v AC really wouldn't make more sense. I think you need to revisit your electrical theory studies.

        2. Saadyasree

          Re: What are they going to do with the heat?

          Heat doesn't radiate well in the vacuum of space. they are surprisingly expecting 120 V we all knew that we need 240v for any kind of work to be done.

    2. You aint sin me, roit Silver badge
      Trollface

      Re: What are they going to do with the heat?

      Build massive underground heat conductors then when you fire it up it will make the moon all nice and toasty, melt the ice, and provide an atmosphere. I recall seeing a programme all about it - admittedly it was on mars and there were some objections to firing it up, but it worked fine...

      1. MyffyW Silver badge

        Re: What are they going to do with the heat?

        Quaid, is that you?

      2. Fr. Ted Crilly

        Re: What are they going to do with the heat?

        No, no Moho, ask the Sabishii to start a dragon for you.

    3. Spherical Cow Bronze badge

      Re: What are they going to do with the heat?

      If you follow the "musings" link you'll find they are talking about enough power for eight houses on Earth which isn't much at all. I suspect the main reason enormous cooling towers aren't required is they are not producing enormous amounts (e.g. one million houses) of power like a typical Earth-based nuclear power station does.

      1. Graham Cobb

        Re: What are they going to do with the heat?

        I suspect the main reason enormous cooling towers aren't required is they are not producing enormous amounts ... of power

        I suspect the main reason enormous cooling towers aren't required is that cooling towers don't work well with no atmosphere.

        I don't think radiators would look anything like cooling towers, however much power you were generating.

    4. Anonymous Coward
      Anonymous Coward

      Re: What are they going to do with the heat?

      Radiate it into space. It's very efficient when things are hot because it scales to the 4th power of temperature. Just make sure the panel isn't facing anything else hot (like the sun) at the time.

      1. John Brown (no body) Silver badge

        Re: What are they going to do with the heat?

        You could probably just put a relatively lightweight sun shield up to protect the radiators. Something like those Mylar blankets they give to fun runners. Or drop the whole unit into a crater deep enough that it gets no sun light, which shouldn't need to be all that deep at the South Pole. The will also help with making the BlinkenLights appear more flashy and SciFi-like.

        1. phuzz Silver badge

          Re: What are they going to do with the heat?

          "Something like those Mylar blankets they give to fun runners."

          You know they call them "space blankets"? It's because they're a spin-off from the space program, most of the outside of Lunar Module was made of it (it looked gold because it was covered in a layer of Kapton).

    5. Swiss Anton

      Re: What are they going to do with the heat?

      Would that be a really hot cup of tea?

  2. Neil Barnes Silver badge

    Dear NASA, please find enclosed...

    Plans for 1 (one) space-ready fission generator. It meets your weight and serviceability requirements, and includes 1 (one) service technician and accommodation.

    Don't worry: he's part of the package. And he's not an astronaut, per se, just a technician, so he won't be hogging the glory. As an added incentive, should any other technical or maintenance tasks be required, his services will be available at very reasonable rates, to be negotiated.

    1. Michael Habel Silver badge
      Boffin

      Re: Dear NASA, please find enclosed...

      Then we will send him cheezy moveies, the wost we can find.

      1. JCitizen Bronze badge
        Devil

        Re: Dear NASA, please find enclosed...

        @Michael Habel - you beat me to it!

        In the not too distant future,

        Next Sunday A.D.

        There was a guy named Joel,

        Not too different from you or me.

        He worked at Gizmonic Institute,

        Just another face in red jump suit.

        He did a good job cleaning up the place,

        But his bosses didn't like him & they shot him into space!

        We'll send him cheesy movies,

        The worst we can find...(la! la! la!)

        He'll have to sit & watch them all,

        Then we'll monitor his mind...(la! la! la!)

        Now keep in mind Joel can't control,

        When the movies begin & end...(la! la! la!)

        Because he used those special parts,

        To make his robot friends --

        source: https://www.lyricsondemand.com/tvthemes/mysterysciencetheater3000lyrics.html

  3. Kevin McMurtrie Silver badge
    Paris Hilton

    Nukes on a moon?

    Earth's moon? Ordinary solar panels from the hardware store should do better than 10 years of 10 kw from 2000 kg. Fancier solar panels should work on Mars too if you periodically wipe the dust off.

    If I was on the moon or Mars, I'd prefer the solution that can take emergency repairs using simple tools.

    1. Hubert Cumberdale

      RTFA...

      "solar power won’t be enormously useful or reliable in the South Pole location planned for US Moon bases"

      1. Anonymous Coward
        Anonymous Coward

        Height

        There must be high terrain near the pole that is in permanent sunlight from some direction or another. The crater floor may be in permanent darkness, but not the rim

        Grabbing sunlight close to the horizon is not a problem on an airless world

        1. DS999

          Re: Height

          There has been at least one crater location identified which I believe is in perpetual or near perpetual sun. If so it will be a very popular area to set up a base.

          Even so, it probably makes sense to have some backup power, since having all your solar panels in a single location makes them vulnerable if something happens to that single location. Wouldn't take much of a meteor strike to take out solar panels located precariously on the rim of a crater - especially if it is a popular spot used by bases for multiple countries. Then there's the chance of deliberate action by a rogue actor, whether an individual 'lunatic' or another country if there's a fight over resources, or just a conflict on Earth spilling over. Or the French, wanting to jump the US claim on all the green cheese.

        2. Aleph0

          Re: Height

          There aren't very many such places I'm afraid, and even those don't get you totally uninterrupted power in all seasons (TIL the Moon has seasons).

          Moreover, if you get there and find that some other nation has already put a permanent installation in place, the Outer Space Treaty prevents you from interfering i.e. putting your own solar panels next to theirs...

        3. Wellyboot Silver badge

          Re: Height

          They'll be after nuke power for a few reasons (1) this will be requirement#1 for any non polar location on our moon (or Jovian moons later this century*) (2) The amount of sunlight hitting Mars is only about 44% of that reaching earth so solar panel arrays will need to be quite large to last ten years untouched (3) Rechargable battery technology isn't up to providing a constant 10Kw/h for 10 years at the 3,500Kg upper weight limit, never mind with the required solar plant it would need.

          Ready for lauch in '26 really means build it very soon and prove it works as advertised for 2-3 years first.

          * not Europa :)

          1. John Brown (no body) Silver badge

            Re: Height

            "solar panel arrays will need to be quite large to last ten years untouched"

            And, as demonstrated by Spirit and Opportunity, on Mars, solar panels can get dusty and you really can't rely on a helpful passing mini-tornado to clean them for you.

            1. DS999

              Re: Height

              Not on the Moon they don't.

              1. John Brown (no body) Silver badge

                Re: Height

                They're asking that the design includes being able to operate on Mars without further modifications.

                1. DS999

                  Re: Height

                  Yes, the reactor, not solar panels. The trick of locating where you could be in sun 24x7 can only work on the Moon. Even if there was a spot on Mars where that was possible, and even if you could avoid dust settling on the panels, you can't stop dust storms that block the sun.

    2. Dave 126 Silver badge

      Re: Nukes on a moon?

      Dust is a major headache on the moon, too. And we're not talking dust like you know it which is rounded due to weathering by wind and water, but very sharp, tiny particles, with jagged edges retained from their formation by meteorite impacts. Over time, objects on the moon accumulate this abrasive dust.

      You could have the solar panels vibrate periodically to shake the dust off, akin to a DSLR camera sensor, but that means moving parts which have to engineered to withstand, yep you guessed it, the abrasive dust. Blowing it off the panels would require a gas that would have to be resupplied. Wiping the dust off would scratch the panels and would again either require a moving mechanism or else be a waste of astronauts time - and any EVA on the moon carries a risk, and causes wear to their spacesuits.

      I don't know much about micrometeorites on the moon, but I know that solar panels would occupy many more square metres than a nuclear reactor of equivalent output, presenting a larger target should meteorites be a risk.

      1. DS999

        Re: Nukes on a moon?

        Why would the dust get ON the solar panels, since there is no wind/atmosphere to loft it. Sure, on the scale of millions of years and many impacts the dust gets spread around, but it doesn't seem like that is going to be a problem for solar panels with a life of 25-50 years.

        It is much more of a problem for the astronauts tracking it inside, getting it in their spacesuits, etc. so they might end up getting some accidentally on the solar panels when they are installed. But once they are installed, and the dust blown off in a one-time activity, so long as no one needs to mess with them again there is no reason new dust would accumulate on them.

        1. JCitizen Bronze badge
          Go

          Re: Nukes on a moon?

          Oh I don't know - maybe rockets coming to and from the moon base? When I saw the LEM blast off from the lander in the moon program, it looked like a helluva dust to me!

  4. Bitsminer

    Credibility

    The notion that DoE could have a new design completed, and approved for use on Earth by the U.S. Nuclear Regulatory Commission within 6 years is not credible. (Use on Earth is necessary for testing purposes.) Assuming it is an actual reactor that is.

    I wonder if HEU (near weapons-grade highly enriched uranium) is expected. They would have to check the lunar surface for little green martians: don't want to violate the non-proliferation treaties by letting LGM get their hands on that stuff, would you?

    1. ClockworkOwl
      Mushroom

      Re: Credibility

      Given the specifications, and timescale, I suspect this is going to be aimed at the current military reactor products or technology. I suspect this won't be a hard spec to reach with HEU, and would also be packagable in a ceramic "ballistic" reentry capsule...

      If the little green martians are already on the moon, a quick melt down might be called for! >

      1. Anonymous Coward
        Anonymous Coward

        Re: Credibility

        I would have thought the core would need to HEU with a neutron poison that is also burned by neutrons, like the 40 year core in the latest subs - you don't what to refuel, so you'll need to have spare reactivity margin that can be "added" as the fusion products build up during normal operation.

      2. John Brown (no body) Silver badge

        Re: Credibility

        "Given the specifications, and timescale, I suspect this is going to be aimed at the current military reactor products or technology."

        Wasn't there some talk in the last year or three about civilian truck sized nuke power plants that could be parked at the edges of towns and cities? Did that ever amount to anything?

        1. JCitizen Bronze badge
          FAIL

          Re: Credibility

          SMRs? They just barely got the concept program started in 2019, and with the super sluggish movement of DOE, it will take forever to come up with designs that can be licensed and accepted by the worthless bureaucrats. There might be one Small Modular Reactor built so far, but it was a light water design, and what we need is Generation 4 or 5 designs, which are so much safer, they are cheaper, and faster to build. However those would take even longer for DOE to even take a sniff at! Hopefully Canada's program with come up with a success.

    2. Spherical Cow Bronze badge

      Re: Credibility

      Finding a location for testing is easy: just bung a few mil at the government of a very poor country with a bit of spare wilderness, there's plenty of those. US regulations don't apply.

  5. Hubert Cumberdale

    Coudn't they have specified...

    ...a proper voltage, like 230V? The US's piddling voltage is one reason it's so hard to get a decent cup of tea there – their mains circuits don't really have enough oomph to power a good kettle.

    1. jake Silver badge

      Re: Coudn't they have specified...

      PDNFTT

    2. MyffyW Silver badge

      Re: Coudn't they have specified...

      ....and the spec says direct current only. Personally I'm an AC/DC kind of girl.

      1. Anonymous Coward
        Anonymous Coward

        Beltway Blues

        I dated a DC girl once. But I had to invert her.

        1. Hubert Cumberdale

          Re: Beltway Blues

          I tried to rectify an AC girl once – she told me not to try it again.

          1. MyffyW Silver badge

            Re: Beltway Blues

            @Hubert is that you?

            Let's just admit it was fun trying...

    3. John Robson Silver badge

      Re: Coudn't they have specified...

      120V DC as well...

      Although in fairness to the US, they do have 240V to each home as shown by

      Technology Connection (YouTube).

      1. Dave 126 Silver badge

        Re: Coudn't they have specified...

        I suspect the lack of air pressure on the moon will be a greater impediment to your brewing a cup of tea than the 120v DC kettle - the water will evaporate before reaching 100 deg C.

        1. Hubert Cumberdale

          Re: Coudn't they have specified...

          I was imagining living quarters pressurised to ~1 atmosphere. If the working pressure were closer to that inside an aeroplane cabin, then I'd say it would be worth designing a pressurised kettle. However, I think if you were attempting to make tea in the ~3 × 10−15 atm of the moon's surface, you'd have bigger problems than getting a decent cuppa.

    4. Boothy Silver badge

      Re: Coudn't they have specified...

      Fun fact....(maybe?)

      Not something a lot of people (outside the US) know, but technically you can get ~240v in US homes. It's usually used for things like air-con, electric ovens, washer dryers etc. If not hardwired in, these have a larger plug with two live connectors, one neutral, and in newer versions, an earth as well in it.

      Unlike the UK, where we have 1 neutral and 1 live wire at nominally 230v coming into the home (ignoring 3 phase, as that's not common in residential places), the US normally uses a centre tapped feed into the house/building (often from a transformer outside), the centre being neutral, and then providing two live wires that are at opposite phases. i.e. live 1 and live 2.

      Connecting between the neutral to either one of these lives, gives the standard ~120v AC.

      The fuse box then typically alternates slots by live 1 and live 2, thus sharing the load. So regular sockets in a US home would be across only one of the live 'taps' from the inbound feed.

      But you can then get double pole fuses that go over both live 1 and live 2, to feed the higher power items like the washer-dryer etc. As these lives are at opposite phases, using this gives you ~240v instead. Although you'd only usually find the heavier duty sockets for these, in utility rooms, garages, behind the electric oven etc.

      1. Stork Silver badge

        Re: Coudn't they have specified...

        In Denmark and here in Portugal it is quite normal to have 3 phases on your fuse box. You then distribute the photos to various sockets and appliances, and if you want you can get a 3 phase socket. Good for charging your electric car.

        Many cookers in DK are 3 phase (to distribute the load between phases I guess, I am no sparky), and we once had one with a phase and neutral swapped in the socket. Water got boiling in no time, and the oven light was rather blinding as long as it lasted. Sparky got the bill for fixing the oven fan.

        1. JCitizen Bronze badge
          Happy

          Re: Coudn't they have specified...

          My fuzzy old mind seems to remember that 3 phase is mostly so one will have advantages ready for three phase motors, which work much better and more efficiently that way.

    5. Dave 126 Silver badge

      Re: Coudn't they have specified...

      > their mains circuits don't really have enough oomph to power a good kettle.

      If 'good' means 'fast', then yeah. Though even a slow (1000W) kettle will still get water to boiling, it'll just take longer (well, as long as it can heat the water faster than heat is lost to the environment). Most British kettles are around 2000 - 3000W, something that was lost on a builder in the pub the other day, who had it in his head that his Honda generator was poorly because it struggled to power a kettle. We all assured him that the genny was fine, and that kettles just take a lot of power.

    6. phogan

      Re: Coudn't they have specified...

      Hot water is hot water, 120V means it just takes a little longer to get to a given temperature. Also tea isn't as popular, you're far more likely to find a coffee maker.

      I had a Zojirushi, it was insulted and made enough hot water for a day and held it at the set temp.

      1. Jimmy2Cows Silver badge

        Re: It was insulted...

        Did you say something to upset it?

        1. You aint sin me, roit Silver badge
          Trollface

          Re: It was insulted...

          Probably just letting off steam...

        2. phogan

          Re: It was insulted...

          Lol nah, I just misspelled insulated.

          1. Anonymous Coward
            Anonymous Coward

            Re: It was insulted...

            We know what you did. We also know what it looked like, which was a lot funnier.

          2. Citizen99

            Re: It was insulted...

            You could have blamed auto(-mis)-correct or predictive text. I would, it's the bane of my life. /rant

            1. JCitizen Bronze badge
              Thumb Up

              Re: It was insulted...

              Good point Citizen99 - but I'm prejudiced because I like your nom de guerre! =)

      2. KSM-AZ

        Re: Coudn't they have specified...

        What exactly does voltage have to do with temperature? That would have more to do with amps/watts. My 60 amp 110v element will heat water faster than your 220v/5a one. I could produce about 6 times the heat(calories,btu's...) Also this is for nasty DC. I don't grok that one. How much ripple do I get?

  6. Chris G Silver badge

    Launch and landing

    It needs to be able to withstand a failed launch and the subsequent hard landing.

    I imagine dropping nuclear reactors several thousands of feet after a sudden ejection from a rocket could be quite threatening to their structural integrity.

    1. Dave 126 Silver badge

      Re: Launch and landing

      I imagine the launch might be designed so that it travels over an ocean.

      1. John Brown (no body) Silver badge

        Re: Launch and landing

        "I imagine the launch might be designed so that it travels over an ocean."

        You still don't want it break open in the ocean. You might end up with mutant sharks!

        1. Intractable Potsherd Silver badge

          Re: Launch and landing

          They just have to make sure that the lasers are on a different launch.

    2. Spherical Cow Bronze badge

      Re: Launch and landing

      Launch sites are already selected for remoteness and a flight path over hundreds of kilometres of sea because hypergolic fuel is very nasty stuff and even if nicer fuels are used nobody wants a rocket landing on their house. So, launching a very small nuclear reactor isn't a problem. Many nuclear powered rovers have already been launched (yes I know the reactor type is very different but the potential contamination from a crashed and ruptured rocket is not so different).

      1. Nifty Bronze badge

        Re: Launch and landing

        Some 40 satellites are up there already with a 1.3-5kw reactor.

        There were some launch mishaps with debris landing in Canada and one burned up over the ocean.

        https://en.wikipedia.org/wiki/BES-5

      2. John Brown (no body) Silver badge

        Re: Launch and landing

        Shhhhhhh....you don't want the anti-nuke crowd hearing that!

    3. Anonymous Coward
      Anonymous Coward

      Launch failure

      A launch failure isn't so much of a problem as the core will not contain irradiated fuel (it won't have been switched on), which means that anything that does gut dumped out isn't highly radio-toxic.

      It would, however, be nice to design the core so that it stays intact (and sub-critical) if the launcher were to come to pieces.

  7. AlgernonFlowers4
  8. RyokuMas Silver badge
    Joke

    More Martian...

    "Don't dig up the box of plutonium, Mark!"

  9. Dave Pickles

    Why the 1Km cable?

    Not everyone likes living next door to a nuclear power station, but even so that's a lot of copper to take to the Moon.

    1. Dave 126 Silver badge

      Re: Why the 1Km cable?

      Yeah, I was to ask how much that cable would weigh. (Or rather, how much mass it has, lest one of you smart alecs replies: "Ooh, roughly one sixth of what it would on Earth!")

      I don't know if they would use copper or aluminium cable... Copper is a better conductor but aluminium is far lighter, making nearly twice as good a conducter per kilogramme. Still, there may be factors such as ductility in extremes of temperature that favour copper.

      If you have power and Luna regolith you could create your aluminium cable in situ, though smelting in the moon is a not yet developed technology.

      1. Spherical Cow Bronze badge
        Facepalm

        Re: Why the 1Km cable?

        Yes you can smelt metal from lunar regolith, so long as you already have a good source of power... oh.

        1. John Robson Silver badge

          Re: Why the 1Km cable?

          Yes you can smelt metal from lunar regolith, so long as you already have a good source of power... oh.

          So you start next to the reactor and smelt the cable away... Does it even need an insulator beyond the first few metres... How conductive is regolith?

          1. John Brown (no body) Silver badge

            Re: Why the 1Km cable?

            Is 10KW enough to smelt aluminium? Is there any ore nearby?

      2. My other car WAS an IAV Stryker Bronze badge
        Boffin

        Re: Why the 1Km cable?

        I was wondering about losses:

        10 kW / 120 Vdc = 83.33 Adc

        Let's go ahead with copper 4/0 AWG (aka #0000), because anything larger is certainly a custom build: 1 km * 0.1608 mOhm/m = 0.1608 Ohms, which leads to... 83.33 A * 0.1608 Ohms = 13.4 V line drop.

        Okay, not as bad as I feared. Boost the sending end to ~135 V and you're sorted; even better if there's proper high-Z sensing lines for feedback (closed-loop control).

        One caveat: Most cable applications assume that losses are going to dissipate to air, and this can be important when building bundles. How do they intend to cool said cable out there? Otherwise, instead of the reactor, the cable itself might just have a... meltdown. [/me dons shades, cranks The Who]

        1. Dave Pickles

          Re: Why the 1Km cable?

          That's about 1600Kg of copper, plus the insulation.

        2. Anonymous Coward
          Anonymous Coward

          Re: Why the 1Km cable?

          I squared R losses would be ~1117 watts, so roughly 11% of the power generated would be wasted heating up that 1km cable - 11.684 mm diameter (copper 4/0 AWG). Well no sorry, the return wire would have the exact same resistance, so it would be double that loss 22% of the power generated would be wasted heating up the 2 km loop of cable. Sounds super inefficient, why is high voltage AC off the table for the transmission line ?

          1. Killing Time

            Re: Why the 1Km cable?

            'why is high voltage AC off the table for the transmission line ?'

            The answer to your question is that the DOE know the means of generating the power is almost certainly going to be a thermopile and the output will be DC. They are not expecting anyone to reinvent the wheel. They are looking for innovation in reactor safety and design, this in turn is likely to come predominantly from materials science and less so from innovative design.

            There isn't any simpler means of generating a voltage (and therefore electrical power) than a thermocouple.

            1. Dave 126 Silver badge

              Re: Why the 1Km cable?

              The German company Nexan claims their superconducting cable carries current equivalent to a cooper cable that has a hundred times as great a cross-section. Colder end of lunar polar temperature is -150 Deg C, Nexan cable operating temp is -200 Deg C... I'm assuming the required cryogenic system system wouldn't have to work as hard. I'm envisioning the thermal insulation as shiny aluminised plastic film sausage skins, since it would primarily be concerned with radiated heat from the sun. Heat transfer by convection perhaps a near non issue in the vacuum? Heat transfer by conduction only by contact with the regolith that is itself shaded by the shiny sausage skin.

              Could it be so well insulated that the cryogenic medium (helium?) is consumed slowly enough that the the exercise is worthwhile?

              Of course the installation would more complicated (as thus likely not as reliable) than laying good old aluminium power cable.

              https://www.nexans.de/eservice/Germany-en/navigate_300014/Technical_Characteristics.html

            2. Dave 126 Silver badge

              Re: Why the 1Km cable?

              Naturally, NASA had already working with universities on superconducting cables. From a NASA piece:

              "Should we ever establish a base on the moon, superconductors would be a natural choice for ultra-efficient power generation and transmission, since ambient temperatures plummet to 100 K (-173 C, -280 F) during the long lunar night--just the right temperature for HTS to operate. And during the months-long journey to Mars, a "table top" MRI machine made possible by HTS wire would be a powerful diagnosis tool to help ensure the health of the crew."

              https://www.nasa.gov/vision/earth/technologies/05feb_superconductor.html

  10. BrazzaB

    Careful with that plutonium

    Hopefully that power plant will not go super critical, blow up and send the moon out of Earth's orbit....

    1. IGotOut Silver badge

      Re: Careful with that plutonium

      So on Earth we are entering the age of 1984 and in space 1999!

  11. LucreLout Silver badge

    Sounds cool though....

    ..... probably a very interesting project to work on.

    How big a heat sink do commentards think this puppy would need?

    What do you do for a living?

    I built a nuclear power station on the moon. You?

    Erm, accounts....

    1. disgustedoftunbridgewells Silver badge
      Holmes

      Re: Sounds cool though....

      Hardly rocket science, is it?

  12. Anonymous Coward
    Anonymous Coward

    Just make sure...

    That they don't send the moon flying out of Earth's orbit when all the waste explodes...

  13. Marketing Hack Silver badge
    Go

    As for the nuclear waste...

    You can store it in a giant, sunken lunar containment facility. I'm sure that if its designed properly, there is no risk that the waste facility might ignite and do something like rocket the moon out of Earth's orbit into outer space!

    (In space, its always 1999.)

  14. A-Yank

    1km cable requirement

    It might be that the 1km cable requirement has more to do with attempting to put as much distance as possible between the reactor and sensitive science equipment whose measurements might be affected by even the minimal radiation that escapes the reactor rather than something intrinsic to the reactor itself.

    A Yank

    P.S. Yes our homes here in the U.S. are mostly 120v except for the big appliances. People who buy electric cars usually have to have 240v service run to their garage if they want the car charged in any reasonable amount of time. On the other hand, 120v is a lot safer if you are fooling around with something and accidentally get jolted.

    1. Anonymous Coward
      Anonymous Coward

      Re: 1km cable requirement

      "On the other hand, 120v is a lot safer"

      It only kills you half as dead

      1. JCitizen Bronze badge

        Re: 1km cable requirement

        Well I know here in the US they always say, "110 kills" - that was because in the old days the voltage could waver up or down from that voltage in AC. But now, it is all pretty much 120 VAC. However I used to be a controls tech, and I can say that getting accidentally zapped by 440 VAC doesn't hurt as bad as ordinary 120 V house current.

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