"Pat Flannery" wrote in message
...

Still a significant amount of energy required per kilogram of material
ending up in HEO.
At some point it makes more sense just to shoot it up from Earth, or at
least from the Moon.

The energy per kilogram is exactly the point. One figure I know off the top
of my head is that such energy costs from the moon to HEO are 1/20 the cost
as from the Earth. And there are some NEAs where the delta-V is even lower
than for the moon. The moon might compete with asteroids if the market is
in HEO, and if the desired material is oxygen, silicon, iron, or aluminum.
The Earth probably won't be able to compete for anything other than stuff
like computer systems or certain kinds of precision (and low-mass) parts.

The other problem is mining the asteroids per-say... solar flux at that
distance is a lot lower than here on Earth, so a major source of free
energy is not as effective.

Making concentrating mirrors bigger ought to be easy in free fall. Having
to double or triple your mirror area might not add that much to your total
material costs since the mirror can be very flimsy.

If you are going to try and colonize them, then it makes more sense just
to leave the material right in the orbit it's in, and build your colonies
out in the asteroid belt itself, rather than using all the energy to move
it inwards toward Earth.

Long-term, I'm sure you're right. But short-term the goal will not be
colonization, it will be making a profit by serving an existing market.
(The colonization will more or less happen as a consequence, not as the
original goal.) So I think asteroidal material will be moved into Earth
orbits because I think the initial enterprises will want to be close to the
markets they serve, and at the onset that's going to be Earth.

But then later on down the road, when commerce with Earth becomes the
smaller part of the space economy, yeah, it makes lots of sense to build
habitats in the Belt. Long-term, more may be built there than anywhere
else.

The Moon is a lot closer at hand for mining, you can walk and drive around
on it, it has a lot more sunlight falling on it, and you have a reasonable
transit time to and from Earth.

The last argument is the strongest.

One of the big problems of this scenario though is that it presumes that
humanity will continue growing in numbers like yeast colonies and
eventually run out of room on Earth to live.

I would agree that, contrary to the expectations of some early 70's-era
supporters, space habitats will not get built to relieve overcrowding on
Earth. They will get built when we become serious about pursuing a destiny
beyond the Earth. But that said, space habitats will permit the formation
of a space-based civilization which may outgrow our planetary one by several
orders of magnitude.

or, in a different timeline, turn the bipedal apes into servants, with
hilarious results somewhere down the line when they learn to speak, and
begin to plot against us. :-)

Heh. I was starting to flash on the current network TV sitcom "Cavemen"
(Neanderthals coexist with modern Homo Sapiens, with hilarious results)
before I saw where you were going with that.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn