Re: Humans doomed without space colonies, says Hawking

From: Robert J. Bradbury (
Date: Sat Oct 20 2001 - 14:17:31 MDT

Adrian Tymes wrote:

> Construction of which was paid for how?

The construction cost for a single self-replicating nanorobot
based on in-place manufacturing methods is essentially $0.
The design cost may or may not be significant. It depends
on how similar the designs for space based nanorobots are
to say medical nanorobots (or how effectively the CAD tools
for nanorobot designs for medical applications lower the cost
of designing those for other applications).

Space development *can* piggyback very easily on developments
for other applications. Note that "nanorobots" are not strictly
necessary, MEMSbots would likely be as effective.

> Designers of said space paid for how?

It doesn't matter. You could simply have them construct a spherical
room. If you use most of the material available is utilized to
manufacture self-replicating construction bots (e.g. utility fog)
then they can form whatever structure you want relatively rapidly.

> Which will be years, probably at least a century or two, later for most
> such rocks. Humans usually aren't that patient. This may change in
> a century or two, assuming greatly extended lifespans come into play,
> but I'm talking about strategy to get space colonized *within* a single
> century.

You have to be assuming that nanotech development fails completely
to believe that we will not be in space in a robust way within the
next 50 years. I myself would place bets on the expansion occuring
in the 2020-2030 time frame.

> Right now? $0, or close enough to make no difference. I'm not
> kidding: NASA might well, say, boost its discarded shuttle fuel tanks
> into orbit if someone where to pay it enough; design studies have even
> been done on it.

That simply isn't true. It looks to me like habitat space is worth
something in the vicinity of $10-20 million per week (once the
development costs are "sunk").

> Asteroid mining, *if one delivers the minerals to Earth to sell them*,
> is one such activity.

I don't think so. To get them to Earth reliably, without vaporizing most
of your payload, you have to have controlled deceleration -- or sufficient
manufacturing capability in space that the heat shield that you vaporize
is made out of relatively worthless material. So you have to lift into
orbit (a) fuel for deceleration; or (b) heat shield manufacturing capacity.
I've never seen anything (and I've read a fair amount of literature on
the topic) that suggests that the calculations for this have been done
and can in fact produce a net profit.

I've said it before and I'll say it again. The proper course of space
development is autonomous *small* partially self-replicating evolving
into fully self-replicating probes that are designed to land on NEOs,
and arrange for transport back into HEO (high Earth orbit) "safe"
packages (those that would burn up should orbital calculations or
something else go wrong) containing useful metals (e.g. Al, Si)
or fuel (H2O). Once the raw materials are available for essentially
"free" one has an incentive to produce designs and develop in-space
manufacturing capacity to produce habitats for tourists, interplanetary
transport ships, etc.


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