Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_5/V13_577.TXT

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Subject: SPACE Digest V13 #577

SPACE Digest                                     Volume 13 : Issue 577

Today's Topics:
    Status of JPL/LMSC 55m dia. Wrap-Rib Antenna Project?
         Powersat R&D (was Re: SPACE Digest V13 #516)
          Re: SPACE STATION FREEDOM WOUNDED
          Re: SPACE STATION FREEDOM WOUNDED

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----------------------------------------------------------------------

Date: 13 May 91 13:57:44 GMT
From: eru!hagbard!sunic!mcsun!ukc!cam-eng![e-mail]  (D.S.C. Yap)
Subject: Status of JPL/LMSC 55m dia. Wrap-Rib Antenna Project?

About ten years ago there was a proposal put forth by JPL and LMSC to
build a large space based antenna.  The reflector was of a wrap-rib design
(structural ribs wrapped around a central hub, then unwrapped at
deployment) and roughly 55m in diameter.  The thing was to go up in a
space shuttle around 86-87, but, of course, the Challenger episode may
have done in those plans.  I need to know the status of that project.
If you know anything about it, could you please email me (our newsfeed
has been flakey).

Thanks a lot.

Cheers,

Davin
--
          .oO tuohtiw esoht fo noitanigami eht ot gnihton evael Oo.
      Davin Yap, University Engineering Department, Cambridge, England
                       -->  [e-mail]  <--

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Date: 16 May 91 08:59:10 GMT
From: snorkelwacker.mit.edu!think.com!spool.mu.edu!munnari.oz.au!mel.dit.csiro.au!latcs1![e-mail]  (Jonathan Burns)
Subject: Powersat R&D (was Re: SPACE Digest V13 #516)

In article <[e-mail]>  [e-mail] (Gary Coffman) writes:

> I'm sorry, but I don't see the big $$ for private industry in returning
> asteroidal heavy metals, or even diamonds, to Earth. The total program
> costs for fetching the materials don't seem at all competitive with local
> sources of the material.

{ E.g. gold, diamonds cheaper to produce on Earth, and launch. }

> Iron, lead, etc are so plentiful on Earth that they aren't even in
> the running.

> What could be profitable would be returning iron, aluminum, oxygen,
> hydrogen, and the like to Earth orbit for use there. Getting rid of
> the launch costs for these *bulk* materials makes sense. However, there
> is presently no market for such materials in LEO, nor is there much
> of a prospect of one in the next twenty to fifty years.

I agree; but that's assuming we're thinking in terms of 1990 demand
for materials and power, expressed monetarily.

Assume 50% per capita USA consumption * 2010 world population, and
some utopian financial regime permitting that population to bid for
same, and it's another story.

Extremes of policy are: keep hi-tech goods unaffordable to half the
world, or develop world resources to the limits.

At some point we have to compare fission breeders on ~1000 GW scale
(counting in all transport & safety costs) with powersats. Maybe
not in 20 years. But I'm very uncomfortable with the idea of living
in 2010, looking ahead to 2040, and powersats still in dreamland.

> The smelters,
> the rolling mills, the fuel refining plants don't exist to use the
> materials. The construction companies that would use the processed materials
> don't exist. The projects those construction companies would build don't
> exist. There is no paying demand for such projects.

Again, I agree. A chicken-and-egg problem which might well keep space
industrialization out of reach for another 50 years. The hope that we
can break out is a slim one. It seems to rest on the prospect of an
industrial revolution happening on paper, identifying the high-profit
areas much more by planning than experiment.

O'Neill changed things by postulating the supply and demand sides
both at once. The colonies need the raw materials, moonbase needs
biomass, Earth needs the power. Too optimistic, fell over. But a
real scenario has to work this way.

> People on this list even want to kill Fred, the first stepping stone
> to building an infrastucture that would generate demand for bulk
> materials in orbit.

We'd all look silly if we had only proposals for generating demand
which squeezed out proposals for generating supply, and vice-versa.

The Nick Szabo line is that there are relatively cheap measures
with high leverage on verifying supply. That is, supply of carbon,
silica, alumina, ore-grade metals: bulk basics. On this, he persuades me.

He also thinks that processing can be demonstrated similarly using
unmanned facilities, taking teleoperation into account. And that
a platform should not be so expensive as to squeeze out these
demonstrations, over the next 10-20 years.

I think the argument whether a manned platform or teleoperation would
better enable the demonstrations still has a way to run. I want to
see a lot more paper work on proposals for processing, before I'm
sure what kind of platform to put up.

> Mining the asteroids for materials to_be_used_in_space makes sense over
> the long term. There is no hurry in the next twenty to fifty years,
> however.

Speaking for space, what we have to sell is sunlight and volume*vacuum.
If we don't have customers for those, we don't have customers.

I want proposals for:

* Very large mirrors
* Large-scale application of carbon-vapour-deposition to custom diamond
manufacture
* Research on non-imaging concentrators, including first-stage smelting,
and monatomic hydrogen production
* Very large scale vacuum-tube technology, including element separation
* Low-gravity magnetic bearing systems in vacuum
* High-intensity-light-pumped lasers
* Tunable free-electron lasers
* Very large radiators

And I want them all to look good enough on paper, that they will justify
either a manned platform or a teleop kit to support the large-scale
versions soon.

I want these things, because in twenty years, I want to _cost_ a terawatt
beamed to Earth. Badly.

I can't prove that powersats will be The demand that kicks space industry
off. That's world politics. However, if the powersats are not at least
costable by 2010, the alternatives in 2030 are: (a) a terawatt of burning
coal (b) a terawatt of fission (c) world-wide industrial deprivation
for lack of power.

How many times have we told friends, "If you're serious about sustainable
growth, you must become a serious supporter of space industry." It is
fairly scary to hear the informed space community saying, "No hurry
for twenty to fifty years."

I don't want to misrepresent you on that, Gary. I know you were replying
to [e-mail], who said:

  >If NASA, a gov agency, could get guys on the moon, in ten years, with
  >National Prestige/Fear the motivation, think what PI could do, with
  >Big $$ as the motivation.  Especially with the experince we have now.

to the effect that the $$ could not be promised. I'm in the awkward
position of having to mark up powersat value against questionable
costs such as greenhouse, large isotope inventories, and/or agrarian
poverty.

But I am certain that powersat demand can be anticipated in the 20-50
year timeframe, as the _first_ benefit of major space industrialization.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jonathan Burns        |  They finally discovered that the ONE thing
[e-mail]|  they just could not _STAND_ was a smartass
Computer Science Dept |  commenting decompiler ...
La Trobe University   |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

------------------------------

Date: 16 May 91 15:49:50 GMT
From: usc!rpi!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: SPACE STATION FREEDOM WOUNDED

In article <[e-mail]> [e-mail] writes:
>>...  They're dreaming if they think it will have
>>more than a momentary effect on their own financial problems.
>
>Even a _momentary_ effect is enough to pay for [various things]
>That's right, _all_ of that, spread over several years, costs just
>one year of peak Fred funding (c. $10 billion by GAO estimates).

Ah, I see.  One year of the mythical peak Fred funding would pay for a
bunch of worthwhile projects.  Has it not occurred to you that no space
projects will ever see that funding if Fred dies?  (Probably not if it
lives, for that matter.)  You're fantasizing here, Nick; my comment
still stands.
--
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  [e-mail]  utzoo!henry

------------------------------

Date: 17 May 91 03:11:09 GMT
From: ogicse!sequent!muncher.sequent.com![e-mail]
Subject: Re: SPACE STATION FREEDOM WOUNDED

In article <[e-mail]> [e-mail] (Doug McDonald) writes:

>>What do you expect? In all government-dominated fields everything
>>seems to degenerate into a zero-sum game.
>
>That is MOST EMPHATICALLY not true: the pie is getting bigger every day.

No wonder my paycheck is getting smaller every day...   :-(


--
Nick Szabo                [e-mail]
"If you understand something the first time you see it, you probably
knew it already.  The more bewildered you are, the more successful
the mission was." -- Ed Stone, Voyager space explorer

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End of SPACE Digest V13 #577
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