# Artifical gravity on spaceships

I wonder if magnetism has any scope for artificial gravity.

Looking at this video of using an extremely powerful magnet to levitate a frog, the frog is reaching an equilibrium point in the middle of the tube, meaning that the forces on it from the magnetic field are pushing it in one direction. If this force is largely uniform across the frog, then it could exert a force in a similar manner to gravity. So perhaps an extremely powerful magnetic field (and a spaceship & crew utterly devoid of anything magnetic!) would be a way to go.

An alternative (which wouldn't be the same as gravity as it wouldn't affect the internals of the people) would be a magnetic suit which is then accelerated by a magnetic field, allowing a person to walk as if they were in gravity, even if their internal organs weren't being subjected to it.

Janus
Staff Emeritus
Gold Member
I wonder if magnetism has any scope for artificial gravity.

Looking at this video of using an extremely powerful magnet to levitate a frog, the frog is reaching an equilibrium point in the middle of the tube, meaning that the forces on it from the magnetic field are pushing it in one direction. If this force is largely uniform across the frog, then it could exert a force in a similar manner to gravity. So perhaps an extremely powerful magnetic field (and a spaceship & crew utterly devoid of anything magnetic!) would be a way to go.

An alternative (which wouldn't be the same as gravity as it wouldn't affect the internals of the people) would be a magnetic suit which is then accelerated by a magnetic field, allowing a person to walk as if they were in gravity, even if their internal organs weren't being subjected to it.

The levitation of the frog in this video is done by diamagnetism. Basically, some material are repelled by magnetic fields. These are materials we generally consider as being non-magnetic.
The diamagnetic effect is very weak, so you need a strong magnetic field to cause a measurable effect.
Some problems:
Such a strong field would be difficult to maitain.
It would likely have negative effects on ship electronics
Diamagnetic materials are not equally diamagnetic. Different objects made from different materials will react differently. This includes parts of your body. The human body is not completely homogeneous, So different internal parts will "feel" a different diamagnetic effect. I'm not sure what the long term effects this would have.

russ_watters
The levitation of the frog in this video is done by diamagnetism. Basically, some material are repelled by magnetic fields. These are materials we generally consider as being non-magnetic.
The diamagnetic effect is very weak, so you need a strong magnetic field to cause a measurable effect.
Some problems:
Such a strong field would be difficult to maitain.
It would likely have negative effects on ship electronics
Diamagnetic materials are not equally diamagnetic. Different objects made from different materials will react differently. This includes parts of your body. The human body is not completely homogeneous, So different internal parts will "feel" a different diamagnetic effect. I'm not sure what the long term effects this would have.

Yes, I did a fair bit of reading into it a while back. I do believe it's worth considering though. It would be difficult to maintain, but that's the sort of problem which is likely to be solvable - it's not like the technology can't exist, it just hasn't needed to yet. Electronics, I suspect that they can be designed to work in a magnetic field, and if the field is known then any effects it has on data signals can be accounted for. You certainly couldn't use off the shelf electronics in there! As for different parts of the body being affected to different degrees, this is no different from different parts of your body being more or less dense than one another in a gravitational field - it just might be different parts which become "heavier"! Long term effects, well, that could only be speculation!

mfb
Mentor
Diamagnetic levitation is doing the exact opposite of what you want. It's a volume force that reduces internal stress and external forces on the body.

It's impractical, too: Scaling up the magnets would be extremely challenging, would come with a huge mass, and it's terrible if you want to move around in these strong fields.

DaveC426913
Gold Member
Diamagnetic levitation is doing the exact opposite of what you want. It's a volume force that reduces internal stress and external forces on the body.
Aside from the impracticality of using magnetism, surely the idea would be to offset the centre of the magnetic force within the ship, so that the levitative effect has a bias in the direction of the decks. Essentially "lifting" them downward.

mfb
Mentor
You can't. Diamagnetic levitation is resisting motion relative to the magnet. A magnetic field that's bound to the ship will always reduce the effective g-force. You can try to make it time-dependent but then it won't last long and will make the astronauts sick.

Staff Emeritus
2021 Award
Diamagnetic levitation is resisting motion relative to the magnet.

Is that what it is doing? Or is it providing a force in the direction of lower field? (That won't work either, of course.)

mfb
Mentor
Ah right, that's limited to high temperature superconductors, and coming from flux pinning not their ideal diamagnetism. You still have some resistance from Lenz' law.
Getting a large field gradient and large field over a large volume is really hard. Wikipedia lists 1400 T2/m for water. A 50 T average field at a gradient of 30 T/m? What cools these magnets?

Perhaps it would be better to have a larger ship with a lower acceleration?

It doesn’t have to be 1g, does it? How much below 1g would humans still be able to retain normal biological functions and musculoskeletal integrity. It would be considerably less energy to accelerate at 1/3 g than 1g, or to spin a habitat to that level. It all depends on what we need to thrive over the long haul. Living on Mars or Moon at their reduced gravities would tell us a lot.

mfb
Mentor
We don't know. 1g and 0g are the only points where we have long-term data.

russ_watters
Mentor
It doesn’t have to be 1g, does it? How much below 1g would humans still be able to retain normal biological functions and musculoskeletal integrity. It would be considerably less energy to accelerate at 1/3 g than 1g, or to spin a habitat to that level. It all depends on what we need to thrive over the long haul. Living on Mars or Moon at their reduced gravities would tell us a lot.
It's likely that physiological effects vary with g (maybe even proportionally), but there are many practical reasons why partial g might be of value. Just the part about everything not physically attached to a wall floating away is a big issue.

I think another big plus would be the accomodation of natural bodily functions. I get the impression that zero-gee toilets are not for the faint of heart.

bob012345 and GTOM
bob012345
Gold Member
It's likely that physiological effects vary with g (maybe even proportionally), but there are many practical reasons why partial g might be of value. Just the part about everything not physically attached to a wall floating away is a big issue.
Variable gee would be useful for outbound and homebound voyages from Mars where the acclimation could be done gradually and naturally each way.

russ_watters