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>From OTA@S1-A Tue Oct 20 03:50:32 1981

SPACE Digest                                      Volume 2 : Issue 16

Today's Topics:
			      Administrivia 
	   SPS vs. Fusion - A response to REM / counterresponse
			 Selling SPS as a weapon
			      SPS as weapon
	     Radiation pressure and and how it applies to SPS
	 Addendum to my previous message about radiation pressure
		 Drawbacks of SPS, hazards of fission use
			   Begg talk at Hahvahd
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Date: 15 Oct 1981 2255-PDT
From: Ted Anderson <OTA at S1-A>
Subject: Administrivia 
To:   space at MIT-MC  

The distribution of the SPACE Digest has changed venue.  It is now being
run from site "S1-A".  The only change you should notice is that this
system does not allow anonymous FTP so send mail to SPACE-REQUEST@MC to
request back issues or whatever.
	-Ted Anderson

P.S. Naturally, if I elect to take a vacation for a few days, you can
count on the space digest automatic distribution system screwing up as
soon as I leave.  So tonight we have four days submissions for the price
of one.
	-ota

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Date: 16 October 1981 10:31-EDT
From: Robert Elton Maas <REM at MIT-MC>
Subject: SPS vs. Fusion - A response to REM / counterresponse
To: DIETZ at USC-ECL
cc: SPACE at MIT-MC

One quibble.  As far as we know there's no single "bullet" that
can kill fusion.  But there just might be, we don't know.  Maybe like
the second law of thermodynamics (negentropy can't be increased),
there's another basic law of physics that says you can't confine
fusable fuel long enough to make it fuse continuously unless
you use a gravitational well to do it.  If so, the only way to
use fusion energy is to explode bombs (unless you have a black
hole or a star handy). -- This is just idle speculation.  Don't
take it too seriously.

Otherwise: you have some good points.  My answer, let's hurry and
get funding to start space industry.  The sooner we get started,
the sooner we'll know what is practical and what isn't.
However, I quibble a little with your problems.  You don't need
to have the factory run in a vacuum. If necessary, you can
run most of it inside a chamber containing a nitrogen atmosphere.
Gravity can be simulated by rotation.  I also have confidence
that moon materials can be electrolyzed into individual elements
if necessary, at which point you have the same elements to be found
on Earth and thus no new problems not already encountered here.

Does anybody know if anybody has actually tried processing
some of those moonrocks brought back by Apollo? Or are they
so valuable nobody wants to damage them?

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Date: 16 Oct 1981 1530-CDT
From: Jon Webb <CS.WEBB at UTEXAS-20>
Subject: Selling SPS as a weapon
To: space at MIT-MC
cc: cs.webb at UTEXAS-20

(I sent a couple related messages on this subject to ARMS-D)
Who's got the bucks?  Well, it sure ain't the Department of Energy or
NASA, who might build SPS as a energy or space system.  And the energy
industry here has way too many sure things they can do will all their
money to build a risky, expensive thing like SPS.  So we need a new
source of funding for SPS.

What does the US need?  Energy?  You've got to be crazy.  When was the
last time we had a gasoline crisis?  It's been years.  And there is very
little support for the space effort nowadays.

What the US needs is POWER.  Not energy, but political power.  SPS
provides a unique source of that power.  

With a concentrated SPS beam (say, 4-6 times regular sunlight) we can
destroy crops.  We can evaporate rain clouds.  In short, we can really
screw up a third-world country we don't like.  For example, suppose we
wanted to punish Khadaffy for his recent inflammatory statements.
Zappo!

And a lot of heat can mess up an industrialized country, too, but
consider what a microwave beam could do.  Microwaves are suspected of
causing bad things like cancer, cataracts, and heart attacks at
extremely low densities.  There would be all kinds of nasty uses for a
powerful microwave beam that could be projected from orbit.

Finally, SPS (as a weapon) provides a literally visibly symbol of US
power.  You could see it at night.  It would be up there, over our
heads.   
 
Think of a huge hand, holding a magnifying glass 22,400 miles above our
heads.  On the wrist is tattooed "U.S.A."  And think of the
command-and-control you can do from there.  I can think of no better
place for a general (or even, maybe, for our president) than in orbit.

Plus, in peacetime, the thing can be used as an energy source.

Jon

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Date: 16 October 1981 22:08-EDT
From: Gene Salamin <ES at MIT-MC>
Subject: SPS as weapon
To: SPACE at MIT-MC

     Well, if an SPS is constructed with the intent of maybe using it
as a weapon, then it will be designed so its phased array transmitter
does not require a pilot beam when in weapon mode.

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

From: FONER@MIT-AI
Date: 10/16/81 23:16:07
Subject: Radiation pressure and and how it applies to SPS

FONER@MIT-AI 10/16/81 23:16:07 Re: Radiation pressure and and how it applies to SPS
To: Space-Enthusiasts at MIT-MC
This is a subject that was covered in some depth about a year ago on
this very list.

While I do not remember exact figures, and do not want to go through
the required calculations to find out again, they exist in archives
somewhere.

The basic ideas are as follows:  you get a particular amount of
radiation pressure from the sun.  This is not much...  maybe a thrust
of a few (500?) newtons (this is the same force as applied to about a
50 kilogram weight in 1 G for nonphysics fans).  Not much.  (Note I
assume a "typical" collector area of some tens of kilometers squared.)

You also get thrust from the beam pressure as well.  An initial
calculation showed this to be on the order of maybe 5000 newtons, but
that was later changed to about 20 newtons (40?).  Something like
that.  Very little thrust, and very easy to compensate for.

Could someone with more time and a higher-speed connection to MC see
if he or she can find the relevant letters in the archives?  I'm
pretty sure they were just about a year ago.

Have fun.

						<LNF>

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

From: FONER@MIT-AI
Date: 10/16/81 23:18:04
Subject: Addendum to my previous message about radiation pressure

FONER@MIT-AI 10/16/81 23:18:04 Re: Addendum to my previous message about radiation pressure
To: Space-Enthusiasts at MIT-MC
It occurs to me that the subject may also have been germane to the
Energy@MIT-MC list.  It's quite possible that I'm confused, and that
the old messages on SPS radiation pressure were sent to that list and
not this one.

Anybody wanna search that archive, too?

Ciao.

						<LNF>

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

Date: 19 October 1981 01:48-EDT
From: Jerry E. Pournelle <POURNE at MIT-MC>
Subject: Drawbacks of SPS, hazards of fission use
To: HASTINGS at CMU-20C
cc: SPACE at MIT-MC

Re vulnerabilities: are supertankers safe from enemy action?
Even anonymous enemy action? Surely it is easier to knowck ouot
an oil field or the Alaska pipeline than to knock out an SPS.

But yes, they are somewhat vulnerable. 

Re fission and operators, I'm willing to give up fission if we
can have space power systems; what will happen, though, is that
SPS is now opposed in the name of fusion; but when fusion will
actually work and put kw into the system, they'll have lots of
reasons why it shouldn't be used either.  The anti-Amerika Krowd
isn't so much opposed to any particular technology unless it
would WORK...

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

Date: 19 Oct 1981 2220-EDT
From: J. Noel Chiappa <JNC at MIT-XX>
Subject: Begg talk at Hahvahd
To: space at MIT-MC
cc: JNC at MIT-XX, mph at MIT-XX, ludwig at MIT-XX, wayne at MIT-XX

	I just got back from a talk that he gave at Hahvahd to the
Astro society there. My general impression of the man is that he
is not a 'politician', honest to a fault, seriously interested and
committed to space, and enough of a realist to deal with running
a major government agency. In short, I am impressed.
	His talk was not too interesting, but the questions/answers
afterward were a gold mine. The only interesting thing in his talk
was that he gave prominent mention to the LEO station as a major
goal after SpaceTel, Galileo and VOIR. He was also interested in
remote operated moon mining stuff in the medium (10 year) range.
Sounds familiar!
	As to the questions: he made a strong commitment to keeping
the Deep Space network running, and to continuing with the Voyager on
to Uranus and Neptune. He feels that there is growing commitment to
space among the general population and in Washington as its role as a
technological ground breaker is appreciated more (there was an
undertone of competitive nationalism against Japan/Europe in this).
He feels that the big policy statement from the OSTP will be a long
time coming and not be very forceful when it does. His most important
operational commitments is getting the shuttle operational and
economic (he had two less important ones, the second of which was
laying long-range plans, but the other has faded from memory - it
might have been keeping appropriations from further cuts). He is
encouraging to commercial commitments, and hopes to see them grow. He
is very interested in getting new starts out of Congress in the two
year time frame. He thinks that NASA has not been hit much harder than
other agencies, and in fact thinks it has come out fairly well. He
made the point that the budget has been dropping continuously for many
years, and the relative importance of space science within the NASA
budget has stayed constant, but that the overall cuts have affected
it. He feels that the Europeans, although very mad over Solar/Polar,
are still very interested in continued cooperation.
	That's all I can dredge out of my (and several others') memories.
He seemed quite optimistic, and I guess I do too, after hearing him.
			Noel
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End of SPACE Digest
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