🚀 go-pugleaf

I recently sent this to the AltInst email list (altinst@cco.caltech.edu).
Comments are welcome, as long as they're constructive.  :-)
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One of the problems facing astronauts who stay in space for extended periods
of time is that of weightlessness.  Astronauts suffer from a form of acceler-
ated osteoporosis, making their return to a 1-g environment increasingly
difficult over time.  Exercise regimens have only been partially successful
in slowing bone loss & muscle atrophy.

In a space station, one can simulate gravity with centripetal force.  This
idea is nothing new; sci-fi movies from the 60's & earlier depict giant
rotating wheels & cylinders orbiting Earth, their inhabitants residing on
the inside of the rim.  However, if one were to start a colony on the moon
or Mars, it would seem that you'd have to be content with living in the
reduced-gravity environment.

What I propose is an alternate, hybrid colony which incorporates the arti-
ficial gravity of a rotating space station.  The basic concept would be to
build the full-gravity section of the colony atop a giant superconducting
flywheel, levitating it above the surface.  It would then be free to spin
so as to compensate for the reduced gravity.

I've done a few minor calculations, and there are a lot of equations and
numbers left for others more knowledgeable than myself to fill in.

For a lunar colony with a capacity for 1,000 people, let's allow a full-
gravity environment of about 314,160 m^2.  (I picked that number because
it works out nicely in the equations.)  This would be for residences, some
businesses, parks, limited roads, etc. and works out to be about 314 m^2
per person.  (I figure about 100 m^2 each for residence, business, & other
miscellaneous areas per person.  Yeah, I know that makes things a bit
Spartan....)  For a colony wheel 20 m wide from inner radius to outer radius,
that's a radius of 2,500 m +/-10 m, or about 5 km across.  The moon's gravity
is 1.67 m/s^2.  Thus you'd need a rotation of 155.4 m/s (rotation period =
101.08 s) in order to generate a 9.66 m/s^2 centripetal acceleration which,
when coupled with the lunar gravity, yields an artificial gravity of 9.804
m/s^2, or about 1-g.

To generate a 1-g environment on Mars, you'd need a centripetal acceleration
of 9.12 m/s^2.  I couldn't find Mars' gravity, so I calculated it to be 3.60
m/s^2.  The Mars colony would have v = 151.0 m/s and a period of 104.03 s.
Note that in both cases most of the "gravity" comes from the centripetal,
meaning that in full gravity you'd almost be standing on your side.

In both these instances you wouldn't want to have the _entire_ colony under
full rotation.  Farming, mining, and other large-scale or labor-nonintensive
activities could be situated apart.

There are a few difficulties which would need to be overcome in order to
have a funtional colony.  First, we'll need to develop a superconductor
suitable for the task.  It would need a sufficiently high Tc (critical
temperature) for the lunar/Martian surface.  (It could be insulated, tho
that would add considerable weight to it.)  I imagine it would also need a
high critical current Jc, given the weight it'll be carrying.  And of course
we'll need to be able to manufacture it in sufficient quantities.  I don't
think mechanical stress will be an unconquerable problem, tho the flywheel
will probably need some internal structural support.  The energy required
to get the whole thing rotating up to par would not be trivial, tho once at
speed it should continue to rotate with minimal energy input.  On Mars you'd
lose some to air friction (unless you were to encase everything), and I'm
not sure how people moving about inside would affect its rotation.  There
might also be a problem with degredation of the superconductor over a long
period of time due to radiation, tho this would depend on what it's made of
& how it's protected.

Aside from the flywheel problem, there's the problem of power generation.
Simple solar should be enough to maintain the flywheel at a constant rate.
The rest of the colony would probably be nuclear-powered.  (I recall a story
in "Amazing Stories" about a year ago where lunar colonists mined the rego-
lith for helium-3.)  In the event of a main power failure, reserve power could
be drawn from the flywheel itself--after all, that's what they were originally
designed for.  I'm not sure just how much power it could give before the
colony came grinding to a rotational halt, but something that size carries a
lot of inertia!  Hopefully it should be enough to maintain life support until
the main power source can be brought back on-line.  (And you'll probably want
other redundant power sources as well.)

I hope that others can come up with the specific numbers missing from the
previous two paragraphs so that the feasability of this idea could be fur-
ther understood.  But at this time it looks like an excellent alternative
to present colony designs, which force the human body to adapt to a lesser
gravity and in effect imprison colonists in those conditions.  After all,
who wants to be stuck living on just one planet?
--
Andrew Trapp                                                       ignition;
dreamer@uiuc.edu                                O-                 full thrust
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P.S.  I wonder if there's some tricky way of adapting this for use on a planet
with > 1-g....