Re: Humans doomed without space colonies, says Hawking

From: Adrian Tymes (
Date: Sat Oct 20 2001 - 18:24:20 MDT

"Robert J. Bradbury" wrote:
> 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).

True...once we have self-replicating nanorobots. If we had them, it
would be a perfectly valid strategy to send one or a few to an
asteroid, then construct the means to slow it down out of the
asteroid's non-valuable mass. Only problem is: we don't have them yet.

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

True. But we don't have self-replicating MEMSbots either, yet.

> > 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.

Mmm hmm. And I'm outlining a way to realize that, without having to
gamble on technology not yet developed. (Self-replicating nanotech
easily leads to space, but there's ways to space even if SRN fails.)

> > 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").

So, who pays the development costs? They'll easily outstrip $10-20
million per week amortized over anything short of a decade, and there
aren't any commercial places willing to put up that much money for
non-proven markets. (Governments might be able to, but their funding
is subject to political whims: rely on government funding, and you roll
the dice each year to see if your project still exists. The result is
something about as effective as post-Challenger NASA...)

> > 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.

Crude positioning can put the reject slag into heat shield position, so
(b) doesn't seem too difficult. Alternately, for (a), fuel for
deceleration could be mined from the asteroid itself (for some
asteroids). And there may be a third way: beamed energy launches have
been demonstrated, at least in prototype, but in reverse, they can
decelerate a payload that's dropping towards them.

This archive was generated by hypermail 2b30 : Sat May 11 2002 - 17:44:14 MDT