"Johnson.." writes:

I have been doing a little reading today about artificial gravity and
haven't seen magnetism mentioned at all. This may sound stupid but
couldn't the floor of a spacecraft be magnetized and the crew wear suits
that would be attracted to that floor?

Notwithstanding the issue that strong magnetic fields tend to interfere with
the proper operation of electrical equipment, there is the fundamental
issue that magnetism only affects magnetic materials, whereas the primary
characteristic of gravity and inertia is that both of them affect =ALL=
forms of matter equally.

Furthermore it is not the magnetic _FIELD_ that generates force on an
object, but the magnetic field _GRADIENT_: ferromagnetic materials are
attracted to a magnet because the field strength _INCREASES_ as one gets
closer to the magnet, so that moving them closer to the magnet increases
the magnetic field energy stored in the ferromagnetic object and the
perturbation it makes in the surrounding field. If you put a chunk of iron
in a perfectly UNIFORM magnetic field, it would feel no =NET= force at all
--- it would merely feel a torque that would align it with the field, and
even that only if it was asymmetrical.

Hence, for your proposal to work, one would have to generate a constant
magnetic field _GRADIENT_ of `X' tesla per meter throughout the volume of
the crew space, i.e., it would need to be strongest at the floor, and
linearly decrease with distance from the floor. Also, the so-called
"magnetic lines of force" will appear to be diverging outward from some
point or line source below the floor. This creates a number of problems:

1.) Maxwell's equations plus practical materials considerations impose
physical limits on how large a volume over which one can produce a uniform
magnetic field gradient.

2.) Since most healthy humans tend to be non-spherical, their magnetic
suits will tend to align their bodies along the magnetic field lines ---
which as I said, will appear to be DIVERGING from some point or line
below the floor. This will mean the floors will have to be sharply curved
unless their is a very strong uniform background field imposed along with
the uniform field gradient.

3.) Unless all their tools are non-magnetic, they will attempt to align
themselves along the magnetic field lines. Imagine trying to use a wrench
or screwdriver that is constantly trying to twist itself out of your hand
and line up perpendicular to the local magnetic field.

4.) Ferromagnetic materials are highly nonlinear; hence, if you put two
chunks of iron in a magnetic field, their induced magnetic moments will
cause them to exert complicated and difficult to predict forces on each
other if you get them close together. Likewise for two humans wearing
ferromagnetic suits.


It would be more practical in a spacestation, which runs on photovoltaic,
cause the electro magnetic floor would be a drain on electricity.

I don't think you realize just how LITTLE power the solar panels on the
space station will put out. The =TOTAL= power capability of the ISS is only
110 kilowatts, or roughly a mere 150 horsepower --- about the equivalent
of three or four automobiles running flat out. The power requirements
for your scheme would be ENORMOUS unless the magnets are superconducting ---
and even them, the cost would be large, since it costs a LOT of power to
keep a superconductor cold enough to superconduct (cryogenic refrigerators
consume tens or even HUNDREDS of watts of power for every watt of heat they
pull out of the cryostat!).

In summary, their are multiple reasons why this idea would be both
impractical and undesirable over the entire volume of a space station.
It =MIGHT= perhaps be possible in a very small "exercise room" is a space
station with MUCH more power to spare than the ISS, but I do not see that
happening any time soon.


-- Gordon D. Pusch

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