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NASA is considering a proposal to build a levitating train system on the Moon.

The Moon's surface is often flat and smooth. Maybe building a mobile train colony similar to the movie Snowpiercer on the Moon is possible by creating a complete loop of Maglev track around it.

Moon’s gravity of 1/5 G is uncomfortable for colonization. Would it work to create artificial gravity on the train during acceleration and deceleration? This could be automated to the point of very gentle transitions (similar to how hybrid cars turn on and off).

Also, this could be used to lower radiation risks. As you could permanently live on the train, stopping occasionally to resupply. You then may be able to visit remote areas, thus having higher productivity potential. You may be staying on the peripheral between moon sunset/sunrise, solar grazing while keeping one part of the train exposed to light for vegetation growth and keeping people in the shaded part to limit radiation exposure.

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    $\begingroup$ "The Moon surface is often flat and smooth" - citation needed. $\endgroup$
    – Jon Custer
    Commented May 29 at 17:13
  • $\begingroup$ Welcome user, you may misunderstand how "artificial gravity" works. There is no mechanism, whatsoever, in any way, by which a train could create artificial gravity pointing downwards. You are confusing speed and acceleration. $\endgroup$
    – Fattie
    Commented May 30 at 10:43
  • $\begingroup$ Regarding "radiation", moon houses/bases need to be buried beneath about 30 feet of water to make them habitable permanently, or a couple of feet for occasional use. (Here's an article science.org/content/article/… ) It's incredibly hard to guard against radiation. Being "in a vehicle" has no bearing on this issue. (Indeed if, astonishingly, there were large "cities" on the moon and a train was needed between them, it would have to be fully underground.) $\endgroup$
    – Fattie
    Commented May 30 at 10:54
  • $\begingroup$ @Fattie. Thanks, may be for radiation it’s possible to create Faraday cage around the train carts, by use of static electricity, that would also act as a magnetic field shield, since small sparks can travel in vacuum short distances I believe. It could also repel dust of the tracks. I would prefer train living than underground or lava tubes. I guess this is more of a sci-fi vision. It’s interesting to see where this NASA’s prototype/proposal ends up and if it could be scaled up one day. $\endgroup$
    – estinamir
    Commented May 30 at 12:17
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    $\begingroup$ @estinamir cheers also i direct you to the outstanding worldbuilding.stackexchange site $\endgroup$
    – Fattie
    Commented May 30 at 14:27

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Using linear acceleration to produce “gravity” is impractical. The duration of normal “gravity” would be brief before linear velocity exceeded the design limits of the train.

However, a train on a canted circular track would act as a centrifuge. By choosing a large enough radius for the track, the “rotation rate of the centrifuge” could be below that which causes vertigo on small diameter centrifuges. enter image description here

The principle is a similar idea to this "circle of death" running circuit designed for exercise in Lunar habitats

enter image description here https://www.economist.com/science-and-technology/2024/05/08/to-stay-fit-future-moon-dwellers-will-need-special-workouts

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    $\begingroup$ Thanks. The Moon is probably not as flat of a surface as I initially thought, with periodic hilly areas present, may be that should be enough of an angle for non linear acceleration. $\endgroup$
    – estinamir
    Commented May 29 at 17:35
  • $\begingroup$ @estinamir , the moon is not in the slightest "flat", it is extremely bumpy and rough $\endgroup$
    – Fattie
    Commented May 30 at 10:36
  • $\begingroup$ "hilly areas, maybe that should be enough of an angle for non linear acceleration" I'm afraid that doesn't make much sense. $\endgroup$
    – Fattie
    Commented May 30 at 10:55
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@Woody presents a good case discussing acceleration and artificial gravity aspects of the question.

Other points to consider include, the construction and operation of such a maglev train would be hideously expensive. Developing a energy system to operate the train would be an interesting challenge, but also an expensive one.

The other practical consideration concerning a maglev train, or any aspect of a lunar colony, is how will lunar dust affect things. The Apollo lunar missions indicated some of the difficulties involved.

Concerning exposure to radiation, as with Earth, not all the radiation that both receive originate from the Sun. The cosmos is abounds with radiation from other cosmic entities. Keeping out of sunlight will reduce radiation exposure, but not eliminate it.

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  • $\begingroup$ Thanks. In the past any trans something railways were build with extensive man power. But may be we will have new automated robotic builders with 3d printing approaches. In terms of cosmic radiation exposure, I wonder if Maglev’s magnetic field could be used in some way to further reduce it by extending it over the rail track and along its perimeter. $\endgroup$
    – estinamir
    Commented May 29 at 20:37
  • $\begingroup$ Also in vacuum you have no resistance and superconductivity at low temps. In NASA proposal they plan to use solar panel powered track. In our case if we do the same, since the track is global you should have constant solar power, since it’s sunny somewhere, which gets transmitted everywhere instantly. $\endgroup$
    – estinamir
    Commented May 29 at 22:42
  • $\begingroup$ Purely FWIW, in the NASA note, nasa.gov/directorates/stmd/niac/niac-studies/…, they mention adding solar film to this "track". This would have absolutely no connection to the power needed to run the tiny robots (a couple of feet square) which they propose floating over the track. The amount of "solar power" produced by this track would be utterly tiny, a novelty, enough to run a couple of light bulbs. Solar power is uselessly low powered. Imagine trying to run even a small train using solar panels. $\endgroup$
    – Fattie
    Commented May 30 at 11:02
  • $\begingroup$ I remember the first tiny light bulb by Edison and the disproportionate excitement in the room at the time, we got to start somewhere. A mere 150 years later, look what we are discussing now :-) Side note, curios if a Tesla coil would work on the Moon youtu.be/x7uCAvEhP1E?si=w2BdxU-VmZgtCA9h $\endgroup$
    – estinamir
    Commented May 30 at 13:38
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Well, we don't know if lunar gravity is enough for avoiding the effects of microgravity, humans have never stayed on the Moon long enough to find out (each of the Apollo crews only spent 2 or 3 days on the surface of the Moon), thus artificial gravity may not be necessary if the colony is to be a research station or vacation resort. However, if people are to birth and raise children on the Moon, artificial gravity could better be provided using a spinning bowl shaped habitat with the floor sloped slightly. Alternatively, smaller centrifuges could be used, at least during neonatal care. Whatever habitat design is chosen, it'll either have to be subselenian (the Moon's version of subterranean) or be covered in a layer or two of some radiation blocking material, possibly with some way to efficiently create an artificial magnetic field. Contrary to what @Fattie says, the radiation blocking material could be less than 9 metres thick and still be safe for long term habitation.

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