🚀 go-pugleaf

Thank you for the considered and considerate reply.  I would like to follow
up on a few of the points you made.

In article <1993Jan7.205156.13655@cs.rochester.edu>, dietz@cs.rochester.edu
(Paul Dietz) wrote:
> 

> There are a number of problems with this argument...
> 
>   "We live on a planet with finite resources"
> 
> Finite does not mean limited.  First, the amount present may be so
> large as to be effectively unlimited.  Fertile nuclear materials
> (U-238 and Th-232) fall into this class.  Second, aside from
> nuclear uses, elements are not consumed in use, they merely become
> less concentrated.  The free energy required to extract materials
> goes as the log of the dilution (higher in practice, but practice
> changes).

I see societal problems even bigger than those facing the space program in
siting breeder reactors and the attendent fuel reprocessing facilities and
waste disposal sites.  The Japanese government is already beginning to face
severe pressure to slow or halt their breeder program. A further problem I
see is that all the energy conversion to useable form (electricity) occurs
within the biosphere.  I do not have a feel for how much thermal energy can
be released into the biosphere before it contributes a significant amount
directly to global warming (as opposed to CO2's indirect contribution
through increased solar absorbtion).  Maybe you have some information on
this. I would love to see it (seriously, no flame). Conversion in orbit
with an efficient microwave downlink reduces the amount of thermal energy
released into the biosphere for an equal amount of useable energy. 
Assuming that a nuke plant is 40% efficient and the microwave link is 95%,
the reduction is substantial.

I agree that elements are not consumed, only distributed.  However, it will
in the future require more time, money and effort to collect a given amount
of a material than it does now.  More raw material will have to be mined to
extract what we need, with attendent damage to the environment.  In general
it will become an increasing strain to gather the raw materials that are
need to keep us going.  Space originating materials will never come close
to supplying all that raw goods and energy that we need. I'm not that
naive.  But it might fill the gap not covered by recycling.

> 
>   "Resources are being used up faster than they are being replaced"
> 
> That a resource is limited and not renewable matters only if its
> is very hard to replace with some substitute.  Fossil fuels are
> an example -- there is no reason why we should not be able
> to survive indefinitely without them, if some other source of
> energy is available.

And no matter what we will have to learn to do without them.  And will
probably be cursed by future generations for burning such a useful
commodity simply to heat our homes.

But the source that replaces it must be socially as well as technically and
economically feasable.  Unless the world politic has a very great change of
heart, I don't see nuclear energy being a fundimental part of the
replacement strategy
> 
>   [paraphrased] "Growth is necessary to avoid social calamity"
> 
> Then we are in big trouble, since growth in resource use cannot
> continue forever.  For example, if energy use grows 1%/year,
> then in 10,000 years we are consuming the entire power output
> of the observable universe.

We are in big trouble.  And there is no technical cure.  The societies of
the world including the western industrial ones, must undergo radical
change.  But it won't happen overnight.  In the interum, some effort must
be made to supply world economies that are continuing to grow.  This is
independent, though, of how we do it. I make no claim that this is
justification for a space program, just that something must be done to
supply a growing demand.

> 
> In the short term, however, there is no reason why resource use
> on earth cannot be increased.  There is no reason why we could
> not supply several times the current population with several times
> the current US per capita energy consumption indefinitely.

Yes, but at what cost to the environment?

> 
>    "No inexhaustible energy source on earth"
> 
> At least two are already in the engineering stages (solar and fission
> breeder).
> 
> "Too Expensive!" you may say.  Well, now, yes, but manufacturing
> productivity increases about 3%/year.  It gets cheaper to make things.
> Moreover, if we had to make a lot of solar collectors or nuclear
> reactors, economies of scale would drive costs down still further.
> And it's a lot easier to start down a learning curve when you can
> build smallish things on the ground rather than enormous things in space.
> Realize that the current world output of PV modules would take
> more than a century to make enough to cover one 10 GW powersat.
> Space colonization schemes are implicitly assuming big productivity
> increases.

No, to unreliable.  Terrestrial solar energy has a problem because of
intermittent illumination.  Either a large storage capacity must be
included in the system, or another source must come on-line at night and
during periods of cloud cover.  The large required land area makes solar
problematic for large portion of the world.  Plus places like Cleveland
goes days or weeks with hardly a glimpse of the sun.

It might be a misconception on my part based on media coverage, but it
seems that nuclear plants have frequent shut downs for one reason or
another, often times for days or weeks.  A system that relied on a majority
of its energy from nuclear power would have to have a significant extra
capacity included, or a more reliable source ready to come on line at a
moments notice.

Without a track record, though, nothing can be said for powersats, so this
again probably isn't a compeling argument.  It at least doesn't share the
intermittent illumination problem of land based solar, plus the power
source never goes off-line :-).

I don't think that powersats of any size or number could be built using
terrestrial solar cells.  Launch costs and energy investment alone would
eat your lunch.  On orbit manufacture using in-situ non-terrestrial
materials would seem the only feesible method.  That brings its own set of
problems, but hey, TANSTAAFL.

> 
>    "If we don't go now, resources will be too expensive"
> 
> This "window of opportunity" argument falls apart under close
> examination.  Resource prices have typically fallen over time, even as
> richer deposits have been exhausted.  Moreover, a space program uses
> relatively little in the way of natural resources.  What it does use a
> lot of is labor, talent and knowledge.
> 
> Look at the price of a shuttle orbiter.  It costs more than its own
> weight in gold.  The cost of the elements and energy that do go into
> its manufacture is a piddling small fraction of its total cost.  The
> same is true of an airliner.  The raw aluminum in a 747, for example,
> would cost perhaps a quarter of a million dollars.
> 
> Increased raw material prices would only make a space program *more*
> feasible, by increasing the potential profit.

The price of raw materials in the space program is trivial, but that isn't
my point.  It is the price of raw materials and energy to the entire
economy that is the problem. I think that an increasing drag on the ecomomy
will be felt as these prices go up.  Either the prices of finished goods
must escalate, or the compensation for human effort must decrease.  Both
will result in a reduced standard of living, no facts just gut feel.  In
addition, we will have to expend more and more of our total effort in
simply producing the raw materials.  I don't think it will be very long
before the public has enough trouble keeping their heads above water that
they will not spend any money on something as speculative as the space
program.  That is the window of opportunity I was speaking about.

All this would of couse be obviated if we could just fundimentally alter
human behavior.  Persuade the world's population that the world has enough
people, so please don't have anymore, or at most only a few of you. And
that they must learn to recycle EVERTHING, not just soda bottles and
newspapers.  This must occur at some point in time, but it won't be easy
and it won't happen soon, IMHO.  But in the mean time, do we let a social
window of opportunity to expand beyond the surface of our world slip by.  

I hope I am wrong about the window of opportunity to have a significant
space program, and that we can find ways to live within the means of this
planet to provide. But for what we spend on it, the space program seems
like cheap insurance to me. I say lets continue to learn how to live in
work in space. Lets explore our solar system to see if their are things out
there that we could feasibly use (both on the surface and in orbit). Lets
at least get ready to be able to live and work in space.  Then take another
look and see if we really do need to, or even can, build powersats,
colonies, moon bases and all the rest.

Hey, what is this soap box doing here!  Sorry, let me just climb down off
of here and I'll be on my way :-}.


James L. Felder            (216)891-4019         -My opinions are MINE-
Sverdrup Technology, Inc.  jfelder@lerc.nasa.gov  I think that should
NASA Lewis Research Center Cleveland 44135        cover all bases, 
                                                  don't you.

"Some people drink from the fountain of knowledge -
    other people gargle"