3
$\begingroup$

I have been to the Wikipedia pages on alternatives to gravity, and found the usual alternative forces, with the potential for magnets and the specious Russian claims, but I'm wondering why not just use some kind of magnetic system that, say, if a person wore a special suit or boots, etc., they could walk around and feel the same weight or attraction?

With the energy produced from a fusion reactor, surely enough energy could be produced for diamagnets, no? Or, if this concept is simply totally flawed, then do you know of some other way that so convenient a force as magnetism could be used?

If diamagnetism can levitate and therefore cancel out Earth's gravity for small objects or even a mouse, maybe it could also produce gravity like effects for ships that won't be designed to travel far, but to have excellent attitude control and articulation?

$\endgroup$
  • $\begingroup$ Can you really consider magnetic boots to be a useful surrogate for artificial gravity (such as rotating a habitat to produce centripetal acceleration)? They may be an aid to locomotion within a habitat, but artificial gravity offers other benefits, like making things "fall" to the floor rather than float away into places they don't belong. Apart from the health benefits of having an apparent weight, handling materials like liquids (e.g. wastes) would be much easier if they simply drained "downward". $\endgroup$ – Anthony X Jun 27 '15 at 17:09
  • $\begingroup$ I agree, Anthony, except the problem is that for a ship to have that kind of force it needs to spin, and therefore the passangers need to constantly move in any particular direction, like in Kubrick's classic. If you remember, a good lot of the time, they were all floating around, and only on occasion "jogging" for the physiological effects. Magnets do seem like a convenient alternative if to benefit from acceleration the ship also has to be designed in a very particular way and of course has to accelerate or spin, otherwise we have to float. I don't see it as "one or the other." $\endgroup$ – Private Name Jun 27 '15 at 19:34
  • $\begingroup$ I think it may be more practical to instead have a suit that compresses the body on the length side and makes articulations offer more resistance. Think of how a full body rubber suit two sizes too small would feel. It would force the body to put more energy in each movement. Combine that with magnetic tiles on the floor and iron-lined soles to anchor your body to the ground, and while you won't actually feel gravity it should prevent muscle degeneration and spine decompression enough to make it livable long term. $\endgroup$ – Drunken Code Monkey Jun 29 at 17:08
7
$\begingroup$

The strength of a magnetic field is proportional to $1/r^3$, so if you build magnets into the floor, there's a huge difference in field strength between your head and feet. So using a suit to provide an evenly distributed force on your body is almost impossible. Even if you only use boots with a metal plate in them, you get strange effects. When you lift your boots off the floor, it'll be difficult at first, but will rapidly get easier as the distance increases. This makes it difficult to walk naturally.

Putting the magnet in the boots is a better proposition, you can build an active system to compensate for the changes in field strength: measure the distance between the boot and the floor, adjust the electromagnetic field strength so that the force attracting the boot to the floor remains constant.

You need a really strong EM field for diamagnetism to have any effect. This would cause problems: any ferromagnetic materials in the field would be hugely affected by the field.

$\endgroup$
  • $\begingroup$ Could you elaborate on putting the magnets in the boots? How could such an "active system," whatever such would be, help to compensate for the changes in field strength? Also, why would putting magnets in the boots be better? I suppose in short, magnets seem like too good an opportunity to pass up, certainly something would have to work. Couldn't diamagneticism be used somehow to impose evenly a force necessary for our bones and muscles? Thanks. $\endgroup$ – Private Name Jun 24 '15 at 20:27
  • $\begingroup$ Also, maybe the ship could be designed to accomodate acceleration forces as well as centripetal forces, such that when not moving, people could use such magnetic fields in any particular compartment of the ship to help them. I could understand using spin on a space station, or using acceleration on a ship that has interplanetary objective of several years, but what about a ship that has to travel and stop and travel and stop and so on? Magnets would never benefit us? It seems like too good of an opportunity to pass up in say a mining ship that navigates the asteroid belt. $\endgroup$ – Private Name Jun 27 '15 at 19:37
6
$\begingroup$

Diamagnetic gravity would require absurdly strong magnetic fields. The field strength required is proportional to the product of the field strength and the rate of field strength change; in order to get a reasonably uniform force across a two-meter-tall human, the rate of change needs to be small. A back-of-the-envelope calculation says you're looking for a field on the order of 100-1000 Teslas to provide simulated Earth gravity, stronger than that produced by the largest laboratory magnets -- and you need to provide that field throughout the entire habitable volume, rather than just the few thousand cubic millimeters at the core of a laboratory magnet.

Additionally, such a strong field means the entire spacecraft needs to be made of non-ferromagnetic materials; even strongly diamagnetic materials (such as graphite) are questionable.

(Note that because diamagnetism is a repulsive force, the magnets providing the gravity would need to be in the ceiling, not the floor.)

$\endgroup$
  • $\begingroup$ Hi, Mark. Thank you for your answer. I wonder, could that kind of elecricity be generated with a fusion reactor? Also, perhaps some diamagnetic materials produce stronger forces than others? Or, for example, maybe paramagnetic materials could produce the same sort of opposite force in the floor, which could thereby help the diamagnetic force from the ceiling, such that they neither would need to be as strong and both could assist in evening out the force, versus its being really strong toward either the floor or ceiling but not so much the further away one gets? Thanks $\endgroup$ – Private Name Jun 25 '15 at 15:42
  • 1
    $\begingroup$ It isn't the source of the magnetism that determines "diamagnetic" vs "paramagnetic", but the substance being acted on. Water is somewhat diamagnetic, so it always gets repelled. Levitation depends on the change in field strength as well as the overall strength, so the more uniform the field is, the stronger it needs to be; a completely uniform field cannot levitate anything. $\endgroup$ – Mark Jun 25 '15 at 19:31
  • $\begingroup$ Okay, so, if some highly reactive suit could be worn, a gravity like field could be produced, provided that the field were some specific way, versus being uniform, as you said? Could you give some example of a field wherein such materials could determine a pull or a push? Thanks. $\endgroup$ – Private Name Jun 26 '15 at 21:13
  • $\begingroup$ Mark, if you could please, do you know if a fusion reactor would be enough to power such magnets? Also, for example, couldn't the magnetic field in those parts of the ship where most important be redirected through really (say, futuristically strong) metglas materials such that at least in parts of the ship a consistent force could be installed? Even if it were just under 1g of gravity? I ask about it's being just under 1g knowing of course that for humans such would in all likelihood be detrimental to us in the long-run. $\endgroup$ – Private Name Jul 7 '15 at 10:52
  • $\begingroup$ Current fusion reactors? Not a chance -- nobody's yet managed to build a reactor that produces more energy than it takes to run it. Future reactors might, but speculating on their technical capabilities is the realm of science fiction, not science. $\endgroup$ – Mark Jul 7 '15 at 19:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.