From: 18084TM@msu.edu (Tom)
Newsgroups: sci.space
Subject: SPS feasibility
Date: 13 Aug 92 22:15:17 GMT
Article-I.D.: cs.Bsy0K5.MEF.1
Distribution: sci
Organization: [via International Space University]
X-Added: Forwarded by Space Digest
Original-Sender: isu@VACATION.VENARI.CS.CMU.EDU


>|> I've never seen 'multiple-orders-of-magnitude' projected improvements
>|) in my (limited) studies.

>Many things have to be done many orders of magnitude more cheaply
>than can be done at present.  For terrestrial-launched systems,
>launch costs have to come down about by a factor of nearly 1000.

1000 times?  That seems rather large.  If we consider the cost for
Shuttle launches ($7000/lb, if I remember right), then your'e saying
SPS will only become feasible when launch costs ar $7/lb?  And the
shuttle is on the high end for launch costs, right?   I think that about
any scheme would be possible at $7/lb; point being that costs don't
have to drop that much.  How about $70?  $700?  Even at $700.oo, we'd see
remarkable increases in space activity, including, among other
things, attempts to answer those questions at the heart of the SPS
debate on this thread.

>The cost
>of processing lunar materials has to come down enormously, if you

I wasn't aware that we were processing anything on the moon ;-)

Obviously, you are using projected costs, but, allowing those, since much
of the cost of lunar processing will be launches for supplies, etc., then
any drop in launch costs will be refelected almost immediately in
lunar-processing savings, too.  It seems that these points are not
independent, as you imply above.

>go that route (what's the cost per man hour of a lunar base using
>existing technology?  More than the cost on Freedom).  In general,
>space activities have to be scaled up by multiple orders of magnitude.

Well, current cost for lunar processing is infinite.  If we ever do any
processing of lunar material, there's your many-orders-of-magnitude, as
promised (infinite/any-number-you-can-imagine = many orders of mag. :-)

Serously, wouldn't a drop in launch costs by only a factor of ten imply,
maybe even necessitate, a corresponding increase in space activity?
How about a factor of 2?

>One microwave SPS has more mass than everything ever put into orbit combined.

Despite my doubts about the truth of that statement, I'll agree, but so what?
At one time, Skylab was the biggest space station, Saturn was the
bigggest rocket, etc.  Just 'cause it's big doesn't mean it's impossible.
Especially if we see launch costs drop by even one order of magnitude.
And, natuarally, I'd be remiss if I didn't point out that many SPS schemes
do not launch all the mass, so the mass of a SPS does not necessarily
imply having paid to launch it.

>|> Didn't I once read that solar-power-cells (to pick a competitor off the
>|> top of my head) were never expected to be more than ~40% efficient?
>|> And didn't I see Dennis post a bit about current developments in solar
>|> cells, with the best efficiency listed as 37%, and lots down in the 20%+
>|> range?  This seems to suggest to me that at least one, if not many,
>|> competing technologies have, indeed, reached the upper part of their
>|> 'learning' curves.

>You are in error: "efficiency" is not the correct figure of merit
>for terrestrial PV cells, "cost per peak watt installed" is.  The
>cost per watt of PV cells has over time declined quite rapidly,
>and is not near any fundamental limit.

But, cost of the material, and cost for the land (sun-intercepting-space)
are different things.  That cost/peak watt does not include land prices.
Or does it?   If it does not, then efficiency is a concern.  If land prices
dominate PV cell prices, it is THE concern.  If PV cell prices continue
to drop, then it is only a matter of time (if it isn't true already) before
they will have reached their fundamental limit, as far as massive power-
generation projects are concerned, because of land prices.

>|> Consider oil, for example, where the reserves in many places are
>|> well into the second, and working on the third level of extraction.
>|> (For oil, level 1 is when it comes out the ground for you.  Level 2
>|> is when you must pump it.  Level 3 is when you have to force water or
>|> mud down, to get any oil up.)

>But, in fact, it is getting cheaper to produce oil, because
>of improved reservoir modeling, horizontal drilling, and so on.
>In any case, the cost of oil is dominated by how much OPEC thinks
>it can charge without stimulating alternatives.  The cost of
>production in the Saudi Arabia is less than $3/barrel.

So the price of oil depends not just on the ease of getting it, but also
the market, labor schemes, etc.  Imagine how cheap shuttle launches would
be if the workers were paid comparably to Arabian oil workers.  And $3.00
per barrel still doesn't include x-port, refining, pollution (or pollution
control), etc.  Sure, we'll continue designing and modelling, and finding
cheaper ways to do it.  But oil is fundamentally limited.  It will become
permanantly more expensive, possibly in our life-times.

I can see a pretty good argument against SPS, along the lines of "We are
not yet at the point where SPS would pay high, and, therefore, we'll never
be able to finance the start-up project".  But I get the feeling that
this approach is not what I've seen here.  It seems more along the lines
of "SPS will never be worth it."  Maybe I'm mis-interpreting, but that's
what I see.

Let's try a different tack, just for grins:

I've seem many references to 'space infrastructure' on this net, almost
always along the lines of "I'd like to see, and help build, a self-sustaining
space infrastructure, too, but you seem to think...[flame deleted]."

Setting aside the question of whehter it's good, or whether it can ever be
done, since I agree with both, I'd like to ask:

HOW will it be done without SPS?  Will we be using oil, coal, et.al., to
fabricate all the fuel we use, until the day we can start harvesting
hydrocarbons from space?  Maybe we'll get launch costs down low enough
to make large-scale tourism possible?   We'll harvest heavy metals from
asteroids?  Fusion fuel from the moon?  Or what?

The big question for SPS, regardless of how we get from here to there,
is; Can it pay for itself, fully running?"  If yes, then we work on how.
But if SPS can't pay for itself, fully operational, can anything?
SPS is no bigger a project than any grand space resource scheme, with
the exception that the resource in question is free and (practically) infinite.
If we can't make it with those advantages, how can we make it without?

-Tommy Mac                     .  "                  +
.------------------------  +                      *       +
|   Tom McWilliams; scrub       ,     .                        "        +
|  astronomy undergrad, at     *       +;.     .  '             There is
| Michigan State University   '                      .    "   no Gosh!
|   18084tm@ibm.cl.msu.edu                        '      ,   *
|       (517) 355-2178       ;  +  '                                 *
'-----------------------