Re: alternative to terraforming

From: Michael S. Lorrey (
Date: Tue Jun 06 2000 - 19:54:09 MDT

Doug Jones wrote:
> "Michael S. Lorrey" wrote:
> >
> > Anders Sandberg wrote:
> > >
> > >
> > > Still, I think the hollowed out asteroid idea might be tricky to
> > > implement due to the unknown quality of the rock. After all, most
> > > asteroids have been subjected to meteoride bombardment, which suggests
> > > that there may be cracks - definitely not something you want in your
> > > walls in space.
> >
> > SImply landing and doing acoustic measurements and capacitance measurements
> > should provide very good data on structural integrity. Pentrating radar should
> > work well as well...
> On the gripping hand, rock has lousy tensile strength. Try making a
> beer keg sized 1-bar pressure vessel out of a good piece of granite-
> fairly difficult, and you'll have to select your stone carefully. Now
> try to make one house sized, without piling so much gravel on top that
> the overburden provides more than a bar of pressure- and without
> cracking the load bearing walls. You're gonna *live* in that thing?
> Without a pressure suit? Scares me and I'm fearless.
> Space habitats are inherently tension structures unless they are buried
> beneath about 100 kPa worth of material- which on an asteroid could be
> kilometers in depth.
> For various gee fields, to get one bar with 2500 kg/m3 regolith
> requires:
> Body Gee Depth (m)
> Mars .38 10
> Luna .16 23
> Ceres .05 73
> Eros .001 3700
> Bite the bullet and make steel and fiberglass out of the regolith.
> Hollow rocks are merely caves.

Well, most asteroids really are not anywhere near granite. Ferrous
asteroids are 80% iron, and the rest other metals with only a small
percentage of silica and other stuff.. Any tunnels would likely be lined
with a good think layer of puncture resistant high strength polymer. I
doubt we'd want to use a chrondite or siliceous (sp?) category asteroid
as habitats, but even then, I doubt you'd be depending on the rock
structurally, more as a nice thick shield against impacts from smaller
rocks and radiation. Now, Ceres, as I recall, is suspected of having its
own gravity almost at the same amount as the moon specifically because
it is such a dense metallic rock. If so, I don't think you'd want to
spin Ceres, and its way to big anyways, it would take too much energy to
get it going. My own idea of what to do with Ceres is to move it into
either Venus or Mars orbit to use its tidal influence to get some
tectonic action and an EM radiation field going again.

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