Message-ID: <4ZRVsHu00VcJM0n04M@andrew.cmu.edu>
Reply-To: space+@Andrew.CMU.EDU
From: space-request+@Andrew.CMU.EDU
To: space+@Andrew.CMU.EDU
Date: Fri,  1 Dec 89 01:45:42 -0500 (EST)
Subject: SPACE Digest V10 #292

SPACE Digest                                     Volume 10 : Issue 292

Today's Topics:
		   Re: Why NASA wants to go to Mars
			 Re: shuttle question
	   Re: What's an 'aerospike' booster configuration?
			   RE: Looking down
		   Re: Why NASA wants to go to Mars
	       Payload Status for 11/30/89 (Forwarded)
	      What happens when a satellite comes down?
----------------------------------------------------------------------

Date: 30 Nov 89 01:08:55 GMT
From: visdc!jiii@uunet.uu.net  (John E Van Deusen III)
Subject: Re: Why NASA wants to go to Mars

In article <1989Nov29.013742.11895@cs.rochester.edu>
dietz@cs.rochester.edu (Paul Dietz) writes:
>
> I am amazed that people are supporting a $400 B project that will
> send four people briefly to Mars.  Even if you ignore science,
> what could possibly be the justification for this?

The $400 billion figure is a best-effort estimate of the MINIMUM cost
to avert a MAJOR depression in the military-industrial complex, not
considering any contractors outside of important population states.
Even now there is much consideration being given to reducing the number
a small but significant amount by eliminating certain expenses, for
instance those that are associated with actually GOING to Mars.  This is
especially true in light of how successful this method of cost cutting
has been in the space station program.

The real problem in providing a hard number is related to unforeseen
technical problems.  As an example, although this estimate was made
AFTER it became apparent that the U.S. had won the cold war, time
constraints did not allow the true extent of the S&L problem to be
considered.  Of course the 250 billion stolen from the S&Ls does not
affect the amount required by the defense contractors, but who could
have predicted that California Senator Cranston would be up-to-his-ears
in it?  Now they might have to DO Mars or whatever on a little less.
Of course Senator Glenn is a great friend of the space program; that
might help.
--
John E Van Deusen III, PO Box 9283, Boise, ID  83707, (208) 343-1865

uunet!visdc!jiii

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

Date: 30 Nov 89 17:44:22 GMT
From: samsung!cs.utexas.edu!jarvis.csri.toronto.edu!ists!yunexus!utzoo!henry@think.com  (Henry Spencer)
Subject: Re: shuttle question

In article <27460002@hpcvia.CV.HP.COM> kas@hpcvia.CV.HP.COM (ken_scofield) writes:
>  ...I've repeatedly heard that the shuttle main engines
>  cannot be restarted once shut down.  The presence of a spark plug implies
>  that it should be possible to restart.  So, other than the obvious problem
>  of having no fuel once the tank is dropped, is there some other fundamental
>  reason why the SSME's can't restart?

There is no *fundamental* reason why most any liquid engine can't be
restarted.  The problems come in the details.  It's not necessarily
true that spark igniters can be fired multiple times.  It's not uncommon
to build pumps with "startup seals", which seal the pump beforehand but 
erode away when the pump starts.  Sections of plumbing may have similar
one-shot seals to ensure that flow starts in the right places at the
right times -- it's cheaper and lighter than valves everywhere.  Valves
may be actuated with pyrotechnics, which gives a small light valve that
can only be opened once.  Precooling of components may be needed before
cryogenic fuels start to flow, and the precooling equipment may be on
the ground.  And so on.  There are enough of these complications that
it is generally safe to assume that an engine which isn't advertised to
be restartable is not restartable; it makes it simpler and lighter.
-- 
Mars can wait:  we've barely   |     Henry Spencer at U of Toronto Zoology
started exploring the Moon.    | uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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

Date: 30 Nov 89 17:59:44 GMT
From: zaphod.mps.ohio-state.edu!gem.mps.ohio-state.edu!usc!cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu  (Henry Spencer)
Subject: Re: What's an 'aerospike' booster configuration?

In article <5105@tekig5.PEN.TEK.COM> philj@tekig5.PEN.TEK.COM (Phil Jansen) writes:
>Hi.  I heard that an 'aerospike' rocket configuration would work out to be
>fairly efficient, and eliminate the need for rocket nozzles.
>
>What is an 'aerospike' anyway, and how does it work?

Take a conventional rocket nozzle, roughly bell-shaped.  Turn it inside
out, with gases flowing down around the outside of a tapering spike from
combustion chambers in a ring around the base of the spike.  Odd though
it sounds, this works.  Furthermore, it's an "altitude-compensating"
nozzle.  Normal nozzles have the problem of picking what pressure the
exhaust emerges at (done mostly by picking the length of the nozzle):
exit pressure much higher than local atmospheric pressure wastes energy,
while exit pressure much lower than local atmospheric pressure can
cause turbulence within the nozzle.  Any normal nozzle on a booster is
a compromise, since it has to work over a range of outside pressures.
With the spike nozzle, the flow clings close to the spike when outside
pressure is high, and expands widely when it's low, automatically
adapting to the current pressure.  This improves efficiency.

The spike nozzle has structural and cooling problems with that long
spike sticking down.  It turns out that you can get much the same
effect if you chop the spike off short and provide a small flow of
relatively low-velocity gas (pump exhaust is often chosen) into the
middle.  The main exhaust gas flows down around the central region
of low-velocity gas much as if it were a solid spike.  This is an
"aerospike" or "plug nozzle".  It's light and efficient.  Moreover,
the blunt truncated spike is a reasonable shape for use as a heatshield
on reentry.

The main problem with the aerospike is that nobody's ever flown one.
One hears rumors -- fairly convincing ones, I'm afraid -- that the only
reason the shuttle doesn't have one is procurement politics.
-- 
Mars can wait:  we've barely   |     Henry Spencer at U of Toronto Zoology
started exploring the Moon.    | uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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

Date: Thu, 30 Nov 89 16:26:31 CST
From: pyron@skvax1.csc.ti.com (When in fear, or in doubt, run around, scream and shout)
Subject: RE: Looking down

More than several years ago, while working at a different company, someone in
our group came up with a great gag picture.  We made sign out of a 4x8 piece of
plywood that said:

	  MCD Lab/Crypto says hi
	to the *censored* satellite

Then, everyone stood around it outside while someone went to the top of an 11
story building and took a picture (zoom, f11, asa 64 Tri-X).  It looked great!!
Anyways, we left the sign out until that evening.

About a year later, our customer (who used the bird) came by.  Someone saw the
poster (blown up) and casually commented, "Oh, that's what it was about!"

'nuff said

Dillon Pyron                         | The opinions are mine, the facts 
TI/DSEG VAX Systems Support          | probably belong to the company.
pyron@skvax1.ti.com                  |
(214)575-3087                        | Never let go of what you have until
                                     | you have hold of what you want.
                                     |        - Wing Walker's Creed

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

Date: 30 Nov 89 14:38:22 GMT
From: rochester!dietz@louie.udel.edu  (Paul Dietz)
Subject: Re: Why NASA wants to go to Mars

In article <671@visdc.UUCP> jiii@visdc.UUCP (John E Van Deusen III) writes:

>> I am amazed that people are supporting a $400 B project that will
>> send four people briefly to Mars.  Even if you ignore science,
>> what could possibly be the justification for this?
>
>The $400 billion figure is a best-effort estimate of the MINIMUM cost
>to avert a MAJOR depression in the military-industrial complex, not
>considering any contractors outside of important population states.

I hope you're not repeating the old canard about government spending
necessarily creating wealth.  That $400 B would have to come out of
someone's pockets; this technowelfare program would only spread the
cost of economic restructuring, not remove it (and the taxes would
be a disincentive to real wealth creation elsewhere in the economy).

Also, if we do spend $400 B, can't we at least get something tangible
out of it?  Science, at least, has proved to have tangible value.

>  Of course the 250 billion stolen from the S&Ls does not
>affect the amount required by the defense contractors, but who could
>have predicted that California Senator Cranston would be up-to-his-ears
>in it?  Now they might have to DO Mars or whatever on a little less.
>Of course Senator Glenn is a great friend of the space program; that
>might help.

Senator Glenn is being investigated also because of his involvement
with the Lincoln S&L fiasco.

	Paul F. Dietz
	dietz@cs.rochester.edu

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

Date: 30 Nov 89 22:53:17 GMT
From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov  (Peter E. Yee)
Subject: Payload Status for 11/30/89 (Forwarded)

Daily Status/KSC Payload Management and Operations 11-30-89
       
         
- STS-31R HST (at VPF) -
      
The GST-8 test is running with no reported problems.  ECS 
support, facility monitoring, and environmental monitoring
support is on going.  Cite MUE validation will begin on Friday.
        
- STS-32R SYNCOM (at Pad A) -
       
SYNCOM monitoring continues.  Orbiter payload bay doors were    
opened last night and preps are in work for payload installation
which is planned for tomorrow.  Final inspection of SYNCOM before
installation is scheduled today. 
       
- STS-35 ASTRO-1/BBXRT (at O&C) -
        
Unconnected power harness check, PGSM gimbal support mechanism  
checkout, gimbal latch mechanism, and CCP retest were 
successfully completed yesterday.  IPS retest to continue today.
       
- STS-40 SLS-1 (at O&C) -
        
Rack structural mods on rack 3 and 5 continued yesterday.  
Condensate water servicing GSE prep and validations are on going.
Pyrell foam replacement picked back up again yesterday.  Gas 
component test stand prep and validation began yesterday.
       
- STS-42 IML (at O&C) -
      
No activity.

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

Date: 1 Dec 89 06:03:34 GMT
From: tramp!loughry@boulder.colorado.edu  (J. Loughry)
Subject: What happens when a satellite comes down?


	Solar Max is coming down.  According to the papers, today
"Engineers blew off the solar panels" in preparation for re-entry.

	Why is this done?  To keep the panels from planing in the
atmosphere, thus making it more difficult to predict the point of
impact?  I would have thought they would be very delicate and quickly
stripped away.

	Also, just what *are* "explosive bolts"?  Do they actually
explode?  How can NASA use something like that in close proximity
to delicate liquid-fueled rockets and the shuttle ET?  Just how
violent an explosion are we talking about?

-----------------------------------------
Joe Loughry
loughry@tramp.colorado.edu

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

End of SPACE Digest V10 #292
*******************