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>From OTA@SU-AI Sun Oct 11 04:34:19 1981

SPACE Digest                                      Volume 2 : Issue 11

Today's Topics:
			 Re: SPACE Digest V2 #10
		      A hot time at L-5 tonight??  
	    Bussard Ramjet designs that exceed the speed limit
			    A number of points
		       Long flame on SPS and fusion
			      Budget cutting
			SPS capital intensiveness
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Date: 10 Oct 1981 1304-EDT
From: Bob Kristoff <KRISTOFF at CMU-20C>
Subject: Re: SPACE Digest V2 #10
To: Space-Enthusiasts at MIT-MC
In-Reply-To: Your message of 10-Oct-81 0702-EDT


What is SPS (please)

Bob Kristoff

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Date: 10 Oct 1981 1502-PDT
From: Tom Wadlow <TAW at S1-A>
Subject: A hot time at L-5 tonight??  
To:   space at MIT-MC  

I read somewhere of a scheme to lose waste heat in space without
dumping massive quantities of material (hot oxygen, for example).
The idea was to use the heat to warm up a reserve of powder, obtained
from the Moon.  You then pump this powder in a stream across a strech
of open space, catching it on the other side and recovering the material
but not the heat.  Since the individual particles can radiate fairly
quickly, if you design the stream and catcher properly, you should
be able to lose quite a bit of heat, but not too much powder.

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Date: 10 Oct 1981 1352-EDT
From: KING at RUTGERS
Subject: Bussard Ramjet designs that exceed the speed limit
To: space at MIT-MC
cc: king at RUTGERS

	The limits on the speed of a Bussard ramjet assume that the
kinetic energy (in the ship's reference frame) of the Hydrogen cannot
be recovered.  This might be accomplished, as was mentioned before, by
extracting energy from the stream electromagnetically.  The obvious
way of doing this is to give the ship a strong positive charge.

	Another way of solving this problem is to not slow the plasma
down so much.  It seems to me that it might be possible to have a
long, thin reaction volume.  The plasma would enter the leading end of
this volume, compressed by the ship's fields and slowed only modestly;
it would then react within a long, thin cylinder surrounding the ship
(the reaction volume would be a magnetic field in any reasonably
ramship, anyway; having the reaction take place outside the ship does
not introduce any additional constraint) and the heated, expanding gas
would push against the trailing portion of the ship's field and would
(in the ship's frame) gain its initial velocity and more.  This is
satisfactory for a Bussard ramscoop and (possibly) not for an
Earth-atmosphere ramjet because the reaction "vessel" in the former
case would be non-material and there would be no viscous energy loss.
Besides, I seem to remember that Nasa wanted to build a hypersonic
ramjet once, without slowing the air much, and they expected it to
work.

	The main reason the reaction has to happen fast is that


(1) reaction time <= reaction "chaimber" capacity * plasma encounter rate


	If the chaimber is larger than the ship and can be made even
larger as the ship speeds up, perhaps the reaction could happen at a
more modest rate.

	While any given ship's coils (or supply of monopoles or
whatever) would give THAT ship a fixed speed limit, given any speed
limit we could provide a design for a ship that could meet that limit.

	Another point that should be noted is that, even if we stop
the fuel in the ship's reference frame, and convert the fuel's kinetic
energy into "useless" heat, this heat would be far from useless.
Exhaust velocities of .17c are based on the temperature that can be
reached by a fusion reaction assuming that the fuel starts at "room
temperature" (e. g. 10e8 Kelvin).  If the fusion reaction is thought
of as adding a certain amount of energy to each particle, then it
would set the particles going at .17c for room temperature hydrogen.
If the hydrogen enters the reaction with the particles moving at .17c,
they would come to be moving at .23c (.17*sqrt(2)), which yields an
exhaust velocity of .23c.  This results in net thrust, although less
than a ramship just starting out (.001c) would get.  Eventually a
temperature would be reached at which the fusion reaction doesn't
proceed, but I imagine that that's a high temperature indeed.  (Any
reaction's equilibrium point shifts tords the endothermic direction as
the temperature rises.)
	To put it differently, the thermal efficiency of the rocket
would be nearly perfect because of the high hot temperature, so most
of the kinetic energy that gets converted to heat will be recovered.

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Date: 10 Oct 1981 1443-PDT
Sender: BILLW at SRI-KL
Subject: A number of points
From:  William "Chops" Westfield <BillW@SRI-KL>
To: space-enthusiast at MC
Cc: billw
Message-ID: <[SRI-KL]10-Oct-81 14:43:14.BILLW>
Redistributed-To: space-enthusiasts at MC
Redistributed-By: BILLW at SRI-KL
Redistributed-Date: 10 Oct 1981

Excuse my possibly igorant rambling, but:

1) Budget cuts
The budget has to be cut.  I may not agree with exactyl what and where
Reagen is cutting the budget, but at least he is doing SOMETHING.
Why isnt NASA receiving funding from private industry, if space is
going to be so profitable ?

2) Capital intensivity.
I suspect that if we don't, it is the Japenese that will, as they have
show in the past that they are willing to make big investments in things
that arent likely to pay off for a LONG time.  Russia, et al, is probably
as bad as we are in that respect.

3) Sun shriking ?
I heard on the radio that the sun is currently shrinking at a rate of
about 5 miles per year.  This ties in with a comment someone made a
LONG time ago about neutrino experiments indicating that the sun was
"off" at the moment.  Any comments ?

BillW

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Date: 10 Oct 1981 19:04:07-PDT
From: E.jeffc at Berkeley
To: v:space@mit-mc
Subject: Long flame on SPS and fusion

     I would like to apologize in advance for what has
turned out to be a long flame on SPS, with more than a lit-
tle philosophy mixed in.  Why philosophy?  Because there
lies my principle objections against the SPS.  REM correctly
pointed out that I had forgotten how the SPS worked, but my
mistaken notion of how the SPS worked was not the sole rea-
son why I'm against it.  I shall offer a two-pronged attack
on the SPS - one material and the other philosophical.

     Before I start with the flame proper, I feel a need to
justify attacking the SPS on philosophical grounds.  It
seems absurd to me that I must do so, but such is the world
today.  The world has come to believe that the machine, and
more recently the computer, is a valid metaphor for describ-
ing how people work.  This is pure nonsense, as man created
the machine, and surely the creator is something more than
the created!  And yet the world today goes ahead and makes
its most important decisions as if it were nothing more than
a giant machine or computer.  The seemingly inescapable des-
truction the world is heading towards is the price we are
paying for such beliefs, for machine logic is capable only
of reacting to its entropy-plagued environment, instead of
rectifying the situation through creative thought, as a
human being would do.

     Space represents more to me than military superiority,
profits beyond end, or a chance to move heavy industry off
this planet and into space.  These are reasons that a com-
puter might use, to justify the expense of going into space.
To a human being they can be but secondary concerns.  The
reason why we must go into space is the same reason why this
country of ours grew from sea to shining sea: it is the des-
tiny of man to rule over nature.  If that seems no longer
possible, it is only because we have abdicated that which
made it possible, in favor of cold machine logic.  No doubt
this sounds corny, and that is why the world is in such a
mess; it most certainly would \not/ have been corny a cen-
tury ago, when manifest destiny ruled the hearts and minds
of this land.

     Now on to the philosophical attack against the SPS:
the philosophy behind the SPS is morally bankrupt.  The SPS
would have us live off the table scraps of the Universe,
like some parasite, instead of feasting on the meal itself -
fusion power.  The SPS is in accord with the philosophy of
living in harmony with nature, as the SPS would have us take
only that which nature, of her own free will, provides.
Whether you run to the hills to commune with nature, or go
into space with the latest technology to commune with her,
the philosophy is the same.  A snail darter may have to live
in harmony in nature - it does not have a choice - but man
does not have to, as he can \control/ nature.  No one has
ever reached his full potential by living off that which is
freely provided him, and it is for this reason man must con-
trol nature, and not to live in "harmony" with it.

     Unfortunately, many readers would not consider a philo-
sophical attack a valid one, either out of principle, or
because they hold opposing philosophical views.  And so I
will come back down to Earth, or at least low Earth orbit,
and try once again to give practical reasons as to why the
SPS is not feasible in the near future.

     We do not have the resources to build a SPS.  It's that
simple.  Someone remarked that if all the money spent on
booze in one year were to be spent on a SPS, we could afford
to build one.  That's misleading.  The fallacy of that
remark is that it assumes that the \amount/ of money spent
is more important than \what/ it is spent on.  If the
President were to go on television, and beg that all
citizens donate their booze money for one year to the cause
of building an SPS, and if by some miracle the people actu-
ally did it, and if the money were to be spent on the con-
struction of a SPS, what would the result be?  Aside from a
devastated booze industry, the result would be massive
hyperinflation and no SPS.  Why?  Because there isn't enough
industrial capacity in this country to handle both the nor-
mal demands of the economy (which it can't handle even now)
AND the demands of building a SPS.  The SPS is too capital
intensive!  Before one can be built, our economy has to be
revitalized and greatly expanded - but to do so will require
the removal of some of the bottlenecks restraining it, such
as high interest rates and expensive energy.  Fusion power
can be developed and put into commercial use long before the
first SPS could possibly be built, assuming that it can be
built without straining the economy past its breaking point.
Fusion is not that far away.  Congress last year passed the
Magnetic Fusion Energy Act of 1980, 100 to 0 in the Senate,
and only 7 Nay's in the House.  It mandates a commercial
fusion power plant before the year 2000, and an experimental
one before 1990.  It authorizes half a billion dollars a
year to be spent on fusion research, to be adjusted anually
to account for inflation.  David Stockman has not been able
to seriously cut funding, although he has tried to remove
all funding, undoubtably because Congress approved it so
strongly.  With fusion power as an integral part of our
economy, we would have the resources to build a SPS, but
by then, we wouldn't need to!

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Date: 10 October 1981 22:37-EDT
From: Robert Elton Maas <REM at MIT-MC>
Subject: Budget cutting
To: TAW at SU-AI
cc: SPACE at MIT-MC

Turning off the Voyager before it completes its misson would be CRETINOUS!!!!!!!!!!!!!!!!!!
Everybody who hasn't done so yet, write to V.P. Bush, as mentionned previously.
<Personal request>

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Date: 10 Oct 1981 23:07:59-PDT
From: ihnss!mhtsa!harpo!chico!esquire!ima!yale-co!galloway at Berkeley
To: ima!esquire!chico!harpo!mhtsa!ihnss!ucbvax!space@Berkeley
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Subject:  SPS capital intensiveness

Say WHAT?!  Hate to tell you this, but oil is not a renewable resource, at 
least not in the foreseeable future.  There are problems with SPS, but i don't
think bringing interest rates down is going to help the energy crisis.  Getting
renewable sources of energy will

Tom Galloway @ Yale






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End of SPACE Digest
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