Re: Mining the Sky

On Fri, 29 Aug 2008 11:31:05 -0700 (PDT), CharlesRCaplan@xxxxxxxxx wrote:

Okay, so it's pretty obvious that nickel-iron asteroids would be good
for building things. Methane and other Volatiles found on the stuff
out beyond the frost line are good for reaction mass and the various
things that a colony would need. (air, water, fertilizer, etc...)

But, I'm having trouble figuring out what useful stuff we would get
from Basaltic, Silicaceous, or Carbonaceous asteroids. Silicates would
be used to produce glass and all the stuff we normally use silicon
for, but what about the Oxides? Bulk soil could be made from just
about any crushed/powdered rock, but bulk soil isn't really useful
unless you have building materials to go with it.

Well, for starters, that's probably where you'd actually go for your
nickel-iron alloy. Typical ordinary chondrite asteroids, what I think
you are calling "slilcaceous", are about 10-20% nickel-iron by weight,
and it's a much more convenient *form* of nickel iron. Talk to your
average mining engineer about whether he'd rather inherit a plot of
land with a hundred-foot-thick layer of solid Acme triple-strength
battleship steel armor plate(tm), or a hundred-foot-deep sandpit with
10-20% fine granulated nickel-iron alloy. Neither is worth anything
to anybody until you get it out of there...

Other than that, the stony chondrites are a pretty good source of
quartz/silica, which is also useful for building stuff if your stuff
is going to have windows, and of elemental silicon which is pretty
good for building solar arrays. And if you've got people who want to
eat, you're going to need an awful lot of windows and/or solar arrays.


Would a mining operation on a Silicaceous asteroid be pulling Titanium
out of Titanium Oxides?

Probably not. There's much more magnesium than titanium, and it's much
easier to work with. It's not as good for building hypersonic aircraft,
but you really only need those on Earth and there's plenty of titanium
on Earth. For spacecraft, magnesium is a perfectly good basis for your
light-alloy metals industry.


Iron out of Iron Oxides?

Not likely when you can get your nickel-iron straight, I think.


What useful stuff do you find on Carbonaceous asteroids?

Well, that would be your carbon. Carbon is really, really useful stuff,
again especially so if you've got people who want to eat.

They're also probably your best source of other volatiles this side of
Jupiter, unless you like lifting them up from planetary surfaces. Too
early to tell whether e.g. Martian water will be cost-competitive with
asteroidal water.


(Since they seem to be lacking in hydrated compounds.)

Actually, the most common sort of carbonaceous chondrite (C2M), is
5-10% water and ~2% organic volatiles by weight. And if you're not
willing to deal with "mere" 5-10% ore concentrations, best leave the
mining to someone else. Especially if that's a 5-10% concentration
of something as easy to seperate as water.


Would a asteroid mining company just go straight for the core, or
would they process the entire thing, or would they be looking for rich
ore veins like we do on Earth? Actually since most asteroids just seem
to be rubble piles with really low density, is there even a core to go
after, or ore veins for that matter?

You've hit upon one of the major issues of asteroid mining. Asteroids
are basically just lumps of steel, coal, and/or magnesium-rich silicate
rock. There's stuff you can do with that. The stuff you *can't* do with
just that, you're pretty much SOL.


I suspect in the short term that mining companies would just cherry-
pick the metallic ones, but how about the long term?

I'm guessing they'll cherrypick the stony ones with a modest metal content
and a nicely pre-crushed regolith. Possibly they'll be going after the
platinum-group elements, but those are mostly dissolved in the iron so
the analysis doesn't change much.

Mining carbonaceous asteroids for volatiles will likely be a supporting
industry; even if it's the metals you want, the miners will need to eat
and drink and breathe, there's plenty of need for reactants and working
fluids in the mining and refining process, and their spaceships will need
fuel for the trip home.


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