The old "hollow asteroid" idea

This old idea keeps cropping up. It has a good history, being
proposed by Cole and others, and used in S.F. by just about everybody.
I think it's just easier to envision, than is taking the asteroid
apart down to dust & vapors, and using the materials to build the
hull.

A good image of an asteroid mine (which is perplexing, because it
doesn't show buldozers, open pits, mine shafts, or anything like a
"mine")
http://www.permanent.com/a-mining-cone.gif
>From PERMANENT 1.6: Mining and processing an asteroid
http://www.permanent.com/a-mining.htm

Mike C.
> this perception comes from the notion that the most difficult part
of making a space colony will be building the metal shell.
> one would only have to go to slightly less trouble ensuring the
inside of the asteroid wouldn't leak than in building a hermetic
metal pressure shell.

A quibble:
After reading up on concrete space colonies, I point out that this
also seems like a preconceived notion, that doesn't stand up to
serious study. (The "metal shell". Shepard says that people see space
colonies as aerospace technology, and that means metal skins & such.)
The points made by Shepard are good: you need slightly less metals
to make a concrete shell (over 90% of a colony is just dumb rock
shielding), and the metals are used better this way. The rock
structure is easier to make & service, and is more 'user friendly'.
Shepard wrote that a metal pressure vessel tends to go "Pop!" when
punctured, as any cracks naturally tend to grow & propogate.

JohnWheeler
> The main point of having a hollowed out asteroids is giving a
greater diversity of habitats than every colony being an O'Neill
clone.

I find this hard to believe; look at the amazing diversity of
colonies which might loosely be termed "O'Neill derived". Besides,
if one concept turns out to work best, why would anybody diversify
-except to avoid trademarked/patented designs... The first one will
probably establish many patents, so there might be a bewildering
variety until the "best" shows itself.

Somebody will make a transparent bubble around a hollow asteroid,
just because the picture of such a "hollowed asteroid" in "The
Millennial Project" is so cool. I just doubt that it'll be more than
a curiosity or resort (You can't live in zeroG). Then again, why not
fuse regolith into a concrete mock-asteroid exterior, instead of the
extra difficulty of actually hollowing an asteroid.
I like Niven's "Kobold" (from "Protector") or the asteroid sized
worldlet with atmosphere -granted, we'd need a transparent membrane
for shielding & containment, since we won't have gravity generators
to keep the atmosphere (from Clarke's early drafts of "2001").

Another thing to remember when this idea comes up is that it
specifies a metallic asteroid, and many of these seem to be 90% pure
nickel iron. You obviously wouldn't use a CC or stony asteroid, much
less an old comet core.
Even with a pure metal mass you're probably better off just building
the hull from the mined materials, instead of digging through,
leaving an empty shell. Worse still is blowing the rock itself like a
balloon. (I never understood why you would bother with the extra
dificulty of the quality control of using the water tank-steam
expansion technique to blow the colony.)
If you want a pure metal shell, vapor deposition around a balloon
form would be much more effective. The question remains, why use
metals for this bulk shell, instead of the rock which is waste slag
after you've extracted the metals.

Josh Kane, message #1487
Subject: Re: Planetary Chauvanism, and Zubrin-ites
> mine the asteroids and, after they have been hollowed out, make
space colonies.

Ron Menich
> What is it that makes you believe that it would be easier to tunnel
through an asteroid versus skimming off and processing surface
regolith?

From: "Dr. Omni"
> the matter extracted from a single asteroid of, say, a kilometer
long, could be used to produce dozens of Island One-sized O'Neilian
colonies.

> Besides, while some asteroids are metallic and may have mechanical
strength to allow spinning for artificial gravity, most of them are
crumby carbonaceous potatoes that would disintegrate if spun a little
faster.