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What would be a viable means to simulate and maintain Earth's gravitational acceleration in a future colony built on another planet?

I am mainly focusing on terrestrial planets, where a colony could be built on the surface, such as on Mercury, Venus, Luna, Mars, gas and ice giant moons, minor and dwarf planets where the gravitational constant is less than on Earth.

Or would it instead be a case of a specific physiological adaptation occurring over time to the lower gravitational effects on these planets?

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  • $\begingroup$ I answered, mainly because my answers can also be applied to space craft. But i think focusing on the planets themselves and creating artificial gravity might be more of a physics question, without so much exploration. $\endgroup$
    – user106
    Jul 19, 2013 at 8:25
  • $\begingroup$ @RhysW well, colonies would be a further stepping stone in exploration as they would provide a distant base, once self sufficient. $\endgroup$
    – user92
    Jul 19, 2013 at 8:29
  • $\begingroup$ Yes i suppose that the potential terraforming aspect would also fall under ontopic. $\endgroup$
    – user106
    Jul 19, 2013 at 8:33
  • $\begingroup$ What would the motivation be? What is the point of moving to low gravity planet if they are just going to raise the gravity? $\endgroup$
    – James Jenkins
    Jul 19, 2013 at 15:35
  • $\begingroup$ "What would the motivation be?" Real estate is measured in area. Although planets have more mass and volume, most of it is not accessible. The small bodies have far more accessible surface area than the planets and large moons of our solar system. For an asteroid, the entire volume can be reached. If our goal is to increase living area and resource base, we should ditch planetary chauvinism, smaller bodies offer much more of both. $\endgroup$
    – HopDavid
    Mar 28, 2014 at 13:35

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There are a few potential ways to go about this.

1. Increase the mass of the planet

Obviously, if the mass of the planet is equal to that of earth's then you have the same gravitational attraction (provided the spin is the same, I'll get to that).

For planets with more mass than earth, you would need to decrease the mass to achieve this effect.

That's not easy though so an alternative is

So what if rather than create a gravity field of the same strength we just make it feel like a gravity field of the same strength?

2. Apply a downwards force

This technology doesn't really exist, that I know of, but if one could apply a 'repulsing' effect from the ceilings on each person in the room then the added downwards force would feel like a stronger gravity.

Conversely, if you wanted to decrease it you would want to apply an attractive force towards the ceiling. But once again, these technologies don't exist yet, nor do I have any thoughts on how would create them.

3. Magnetic Boots

To me, this seems like the most viable of the options. Have metallic flooring and boots that are magnetic using electromagnetic induction. This allows you to 'turn on and off' the magnetism. If you are being attracted to the floor by the magnets then you get the advantage of it feeling like a stronger gravity on your legs and holds you to the ground, but your body will still experience less weight and there will still have less weight on those objects that aren't being magnetized.

The best thing about this technology is that it could also be used in a spacecraft for long exploration flights

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    $\begingroup$ @ernestopheles on second thoughts i think i was mistaken, re reading my sources sort of proves the opposite. Thanks for the nudge towards providing evidence $\endgroup$
    – user106
    Jul 19, 2013 at 15:08
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    $\begingroup$ I don't think that magnetic boots simulate gravity in any useful way. I don't see how it puts pressure on the skeleton to prevent bone loss. $\endgroup$
    – LocalFluff
    Mar 24, 2014 at 10:19
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    $\begingroup$ @user39: The Earth's spin does slightly reduce your effective weight if you're standing at the equator. To completely counteract it, it would have to rotate roughly every 84 minutes rather than every 24 hours -- which would cause the planet to fly apart. $\endgroup$
    – Keith Thompson
    Mar 24, 2014 at 22:48
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    $\begingroup$ I agree with Local Fluff, magnetic boots wouldn't put pressure on the long bones and thus do little to prevent atrophy. Applying a downwards force is doable but this can be done without repulsing ceilings. Someone on the moon could simulate earth weight by carrying a backpack 5 times his mass. Increasing a planet's mass isn't practical. I am down voting this answer and up voting Local Fluff's answer. Centrifuges are a practical way to increase gravity. $\endgroup$
    – HopDavid
    Mar 27, 2014 at 20:43
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    $\begingroup$ @HopDavid: the practical downside to carrying a backpack 5 times your mass on the moon is that although the weight is the same as your body on Earth, the inertia is 6 times as much. You can presumably haul it around but once it's moving you really do not want to get your thumb trapped between that thing and a door frame, or have to come to a quick halt once you're up to speed. The practical solution, as you say, is working out in centrifuges for however many hours a day turns out to be necessary. $\endgroup$
    – Steve Jessop
    Apr 14, 2016 at 23:42
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Centrifuges with long tethers (or airbeams) could be used also on the ground. Below is an illustration where the crewed part of the carousel is below ground for protection against radiation. According to the source the centrifugal radius would be 33 meter long to achieve 0.5 g (with 0.17 g given naturally on the Moon).

enter image description here enter image description here

From www.cislunarone.com by Dr. Doug Plata.

Firm ground with useful gravity is indeed a rare resource in the Solar system. Mars and Mercury with 0.38 g might be enough for human health. If Lunar gravity is enough then we have half a dozen other bodies. But then there's Ceres with 0.03 g which certainly is useless.

A more phantastic idea is to build a tunnel inside an asteroid and spin it up so that you'd walk with your feet outwards on the inside of the surface. Future space exploration could be a funny thing!

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I talk about this at What's the minimum spin hab?

We have two data points: 0 g and 1 g. We don't know the effects of partial g. Maybe Mars or Lunar gravity can keep us healthy. Or maybe not.

Valeri Polyakov spent 438 days in orbit yet suffered only minor bone loss. However he had a lot of self discipline and maintained a challenging exercise regimen.

Besides muscle and bone atrophy, drainage is also a problem. We rely on gravity to drain our sinuses, for example. I don't think a full g is needed for liquid to flow down hill. Besides helping with the body's housekeeping chores, partial g could also enable flush toilets, conventional showers, etc. Less troublesome hygiene would be a huge morale booster and improve health (in my opinion).

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    $\begingroup$ Where is the answer to the question asked up top? $\endgroup$
    – TildalWave
    Mar 28, 2014 at 9:43
  • $\begingroup$ "spin habs" -- Spin habs are a viable way to simulate and maintain earth's gravity. In the link I provided is a description of a carousel on a planetary surface. $\endgroup$
    – HopDavid
    Mar 28, 2014 at 13:17
  • $\begingroup$ A latter part of the question is "a case of a specific physiological adaptation occurring over time to the lower gravitational effects...?" Which I believe my answer partially addresses. Effects of partial g aren't known. It's possible we can adapt to Mars or even lunar g. Or not. But at this point the asumption we need a full g is unwarranted. If a martian g is adequate, that could greatly reduce the expense of building spin habs on dwarf planets like Ceres. $\endgroup$
    – HopDavid
    Mar 28, 2014 at 13:27
  • $\begingroup$ OK, so the answer is on your blog? The answer to the question presented at the top should be here, where you submitted it as such. Linking to your blog is fine, if you reckon that's then still needed, otherwise there's no harm in linking to it also on your personal profile. $\endgroup$
    – TildalWave
    Mar 28, 2014 at 17:21
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    $\begingroup$ We're not a forum, this is a Q&A site, so even going by its name alone, the answer is required to be here where the question is. More is explained in our About and Help center, in particular How to Answer. This is not nitpicking, we probably all write our own blogs (or equivalent), bot none have so far just linked to them as an answer (tho perhaps as a comment). In this case, since it's your own writing, you can obviously skip attributions, otherwise we also require any excerpts extracted from external sources to be both marked in blockquote and authors properly attributed, with a link where possible. $\endgroup$
    – TildalWave
    Mar 28, 2014 at 23:27
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Looks like LocalFluff also talked about centrifuges. Here's my take, which is on similar lines.

It would be limiting for individuals to allow their physiology to weaken from lack of gravity (as long as a return trip to a higher gravity at a later date was possible or desired). It may be ok to let the plants and animals adapt, however, which reduces the scope of the problem to maintaining the health of human beings.

Carnival rides on Earth can create higher than earth gravity effects. NASA is already looking into applications of this.

One possible solution for a colony on a lower mass planet like Mars, where there is some gravity but it is still weaker than earth, is to provide centrifuge style exercise areas as big as ferris wheels that spin constantly (except for planned maintenance or no-use time periods).

A pod (that traces an identical circular path) could be spun up to speed to match the centrifuge and docked magnetically. The people inside the pod could be spun up to speed, dock, jog for an hour or lift weights or do squats, then get back in the pod and go home. All this, of course, would need to be refined a fair amount for safety and convenience. However, as long as the centrifuge had a ceiling that was no higher than, say, 12 feet, a person could safely fall to the "ceiling" in the event that the centrifuge lost power (due to the lighter gravity making a fall like this safer than it would be on Earth).

I would imagine that the exercise chamber, if designed like a ferris wheel, would have highest gs when a person standing still has their feet pointed at the Martian ground and the least gs when their feet point toward the Martian sky. So it would require an adjustment period so that people don't injure themselves by miscalculating the amount of gravity at any one moment (i.e. landing too hard). This assumes the exercise chamber doesn't have smart enough motor programming to speed up and slow down to manage the changing gravity.

That would help solve the problem of the whole-body effects of gravity, unlike wearing ankle weights. You could even choose your amount of gravity to be a little higher than earth if that would reduce the time needed for a person to stay strong.

Another NASA article on their explorations with centrifuges.

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    $\begingroup$ Take a look at the centrifuges used to experiment with high G-loads. They spin in the horizontal plane, and contain a bucket that swings out so the "gravity" vector always points at the floor. Much easier than a vertical Ferris wheel. $\endgroup$
    – Hobbes
    May 22, 2016 at 19:46
  • $\begingroup$ @Hobbes That does sound easier and more practical, but I still like the idea of a ferris wheel simply because it doesn't leave you stuck in a cubicle. Instead you could have a whole circular track to run on or otherwise move around. However, that is a psychological concern, not a technical one. $\endgroup$
    – oxalis
    May 22, 2016 at 20:51
  • $\begingroup$ I rode on a carnival ride a couple of times that was called a 'Round-Up'. It started spinning in a horizontal position, the began to tilt until the riders were spinning nearly vertically. At the bottom end of the spin, the centrifugal force was probably around 2 Gs and at the top of the spin, I could lift my entire body off the back mat with one finger on each hand. $\endgroup$
    – Howard Miller
    May 22, 2016 at 23:01
  • $\begingroup$ A horizontal centrifuge can be built with a string of connected buckets all along its perimeter. A Ferris wheel has large variations in gravity (almost 0 to 2G in your example), that's like riding a rollercoaster, not a good environment to work in. $\endgroup$
    – Hobbes
    May 23, 2016 at 10:47
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Creating artificial gravity on another planet or moon could be accomplished the same way it would be done in space, by moving a vehicle in a circle. It would be difficult to move a very large vehicle in a circle such as spinning it, but a smaller vehicle could travel in a circle on a banked track. The system might be similar to cars moving on a banked-track at a motor speedway. Maglev systems would probably work better because of less wear on wheels. The track would need to be about one mile in diameter so that occupants would not feel the Coriolis-effect of moving in a circle as in a small diameter systems. The slope of the track could be varied depending on the velocity required to produced a specific required gravity.

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