Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_1/V10_182.TXT

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Date: Wed,  1 Nov 89 03:21:47 -0500 (EST)
Subject: SPACE Digest V10 #182

SPACE Digest                                     Volume 10 : Issue 182

Today's Topics:
              Re: Galileo Update
                Wood in space
       Re: NASA Headline News for 10/25/89 (Forwarded)
          Re: Space Shuttle SRB exhaust gas makeup.
           Re: "Terraforming", so-called...
       Re:  NASA Headline News for 10/04/89 (Forwarded)
                   Pegasus
             Magellan Temperature
         Re: Asteroids as weapons of mass de
         Re: Galileo and the proposed asteroid flybys
           Re: "Terraforming", so-called...
         Re: Asteroids as weapons of mass destruction
              Re: Final Frontier demise?
             Re: Radar astronomy
----------------------------------------------------------------------

Date: 25 Oct 89 18:06:38 GMT
From: microsoft![e-mail]  (David Levine)
Subject: Re: Galileo Update

|In article <[e-mail]> [e-mail] (Ron Baalke) writes:
|>                                     The 2nd stage IUS spinoff at a rate of
|>2.9 revolutions/second for the separation of the IUS from Galilio sooned
|>followed.
|
|Was this correctly printed ??  The IUS spun itself and the payload up to
|174 RPM prior to separation ??  That seems like an incredible controls
|problem to prevent the stack from spinning in a very wide "cone".  Also at
|actual separation, the CG will jump back some 30-40 feet maybe (don't know
|actual Galileo dimensions) - again sounds like one hell of a controls
|problem.  Was this meant to be 2.9 RPMinutes ??

I would put my vote on 2.9 rev/minute.  This is because Galileo is designed
to spin at 3 rev/minute for stabalization.  It would not make sense to spin up
to 3 rev/sec only to have to waste fuel slowing back down.

As long as the spin was applied properly, it should spin quite evenly, NOT
in a cone shaped pattern (like a top, eh?).  I worked for 3 years at JPL
doing mass properties for Galileo and if we did our job right, the CG should
be < 0.1 inches from the spin axis with a very small a product of intertia.

Of course, at some point during the flight, explosive bolts will pop open
the Spin/Despin Interface and the section containing the scan platform
instruments will be slowed to a halt to provide a non-rotating platform
for observation.

BTW - The SBA (Spin Bearing Adapter) *does* use a mechanical interface to
transmit data between sections.  They had some problems with noise there
but it's since been worked out.

GO GALILEO!!!!!

David Levine

+++++++++++++++++++++++++++++++++++++++++
+++ My employer thinks I work all day +++
+++    These are purely my comments   +++
+++++++++++++++++++++++++++++++++++++++++

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

Date:     Wed, 25 Oct 89 16:14:08 CDT
From: Will Martin <[e-mail]>
Subject:  Wood in space

This message is inspired by a reprint of an old Amazing Stories cover
that was used as an illustration in an ad for pressure transducers in an
aerospace products magazine.  They used the illustration because the
text of their ad starts out "Neil Armstrong transformed a comic book
fantasy into reality with his walk on the moon..." and the cover shows a
1920's or 1930's era visualization of moon explorers, wearing what
appear to be rigid spacesuits with hinged joints, bright red in color,
with what appears to be a communications wire linking the two interpid
space explorers' helmets. (The actual date of the magazine is unknown --
the cover shows just "May" with no year visible.)

Actually, it may well be that this cover was a reasonable scientific
estimate based on the knowledge at the time; it certainly is much more
realistic than the slavering-bug-eyed-monster with the
scantily-dressed-damsel-in-distress that was also common on sci-fi
pulps of the era.  Anyway, one of the features of the equipment hung on
the spacesuits' belts are a number of wood-handled tools: shovel,
pickaxe, & axe (I wonder just what they were planning on chopping down?
:-).  The men are carrying what look like peaveys, with wood shafts and
an interesting touch -- wooden disks on the non-hooked ends; perhaps to
keep from penetrating too deeply into moondust drifts like the disks on
ski poles work in soft snow?  Anyway, that started me thinking -- what
would happen to wood exposed to space?  Consider the effects of vacuum,
temperature, and radiation from the sun -- would wood dry up, crumble,
and disintegrate in a matter of seconds or minutes, or would it remain
strong enough to use for a reasonable length of time?

Was any wood put on the LDEF? Maybe some of the instruments there should
have had a nice Victorian-style mahogany housing... :-)

Anyone have any ideas on this subject? Maybe we can have some nice teak
space yachts at some future date...

Regards, Will

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

Date: 25 Oct 89 21:10:07 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: NASA Headline News for 10/25/89 (Forwarded)

In article <[e-mail]> [e-mail] (Peter E. Yee) writes:
> [Atlantis'] tires and brakes
>have been removed.  Normal scuffing was observed on the tires and
>no damage was reported on the brakes.

Do they replace the tires for every mission?  Or send them back up
scuffed, or repair the scuffs, or what?

--
"UNIX should be used          ::   Tom Neff <[e-mail]> or
 as an adjective." -- AT&T   ::    ...uunet!bfmny0!tneff (UUCP only)

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

Date: 26 Oct 89 02:54:42 GMT
From: agate!typhoon.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Re: Space Shuttle SRB exhaust gas makeup.

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (George William Herbert) writes:
>>    A _dash_ of aluminum???  The majority of the thrust is achived
>>by the aluminum component of the fuel !
>>    The actual materials are Ammonium Perchorate, Aluminum powder, PVC
>>binder and extra bits to stabilize.  It's about 99% those three.
>
>If we're being picky, the numbers (according to NASA) are 69.83% ammonium
>perchlorate, 16% aluminum, 12% rubber (it's not PVC, it's a polybutadiene
>acrylic acid acrylonitrile polymer), 2% curing agent, and more or less
>0.17% iron oxide catalyst.
>
>And don't sneer at the idea of doing without the aluminum, because the
>rubber is also a fuel; similar combinations without aluminum have almost
>as high a specific impulse.  (For that matter, ammonium perchlorate by
>itself is apparently non-trivial as a monopropellant, although it's not
>used that way because its physical properties aren't right.)

    Okay, Henry, you got me :)
I had a tech paper from some time back that had PVC listed as the propellant,
but i checked again and Heny appears to be right.  Maybe it got changed sometime.

    As for the 'no aluminum' bit, it really was described as making
most of the difference.  There's a whole lot more energy in Al than rubber...


****************************************
George William Herbert  UCB Naval Architecture Dpt. (my god, even on schedule!)
[e-mail]  [e-mail]
----------------------------------------

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

Date: 25 Oct 89 16:16:28 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: "Terraforming", so-called...

In article <[e-mail]> [e-mail] (Gregory N. Bond) writes:
>Can anyone explain why Venus, which is smaller and with weaker gravity
>than Earth, has an atmosphere 100x more dense?  Why didn't it just
>escape?  (Conversly, why is Earth's atmosphere so thin?)

Most of Earth's atmosphere ended up in rocks and in the ocean, as I recall.
Venus has lost its oceans, may have less tectonic turnover to expose fresh
rock, and has a less chemically-active atmosphere.
--
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry [e-mail]

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

Date: Wed, 25 Oct 89 10:27:55 PDT
From: Peter Scott <[e-mail]>
Subject: Re:  NASA Headline News for 10/04/89 (Forwarded)

dftsrv!drax![e-mail]  (Loren (Buck) Buchanan) writes:

>It would be tempting to abort the launch, have the people arrested, and
>sue them for damages.  What does it cost to abort a launch (include
>all personnel costs) and add onto that lawyers fees?

A friend and I here estimate a day's cost of launch operations for an
aborted launch at $750,000 - $1,000,000.  Naturally this would be eclipsed
by the lawyers' fees.

Peter Scott ([e-mail])

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

Date: 25 Oct 89 18:08:49 GMT
From: uflorida!beach.cis.ufl.edu![e-mail]  (Bob Slaughter)
Subject: Pegasus

Any word on when the first launch of Pegasus was/will be?  I am interested in
knowing how this project runs.  I saw quite a bit about it about a month ago
on here, but since then, it has been quiet.  Also, could someone point me to
a good overview article on Pegasus, with design illustrations and other basic
info.

Thanks in advance,

--
*     Bob Slaughter                           *  This space for rent       *
*     InterNet#1:  [e-mail] *    Call 1-800-FOR-RENT     *
*     InterNet#2:  [e-mail]      *   Model Railroading        *
*     Bitnet:      Haldane@UFPine             *          is Fun!!          *

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

Date: 25 Oct 89 20:41:29 GMT
From: rochester![e-mail]  (Cesar Quiroz)
Subject: Magellan Temperature

What happened to the temperature problem?  I seem to have missed the
resolution.

Thanks,
--
                                      Cesar Augusto Quiroz Gonzalez
                                      Department of Computer Science
                                      University of Rochester
                                      Rochester,  NY 14627

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

Date: 25 Oct 89 16:10:35 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Asteroids as weapons of mass de

In article <[e-mail]> [e-mail] writes:
>Does anyone know how large an asteroid must be (before entering the Earth's
>atmosphere) in order to not burn up (as do many (most?) meteors)?

Not very big.  The reason most meteors don't become meteorites is that they
are very small.  Something the size of a fist has an excellent chance of
reaching the ground unless it's very fragile.

>How much
>smaller would an asteroid (say a 100m one such as talked about in the previous
>postings) be when it hit the earth's surface?  ...

Unless it's fragile or volatile (e.g. a chunk of fizzled-out comet), not very.
The seriously big ones keep too much velocity and have too little surface
area for their mass; they don't lose much on the way down.
--
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry [e-mail]

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

Date: 25 Oct 89 16:13:57 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Galileo and the proposed asteroid flybys

In article <[e-mail]> [e-mail] (John Kallen) writes:
>Now that Galileo is finally on its way, I start wondering whether the
>launch delays the probe suffered affect in any way the planned
>asteroid rendezvous (sp?)...

I haven't yet seen the launch-window chart for Galileo, but if it's anything
like the one for Magellan, the situation actually gets better with small
delays.  NASA tried to hit the very beginning of the launch window not
because it was the best time, but to leave as much margin for delays as
possible.

>Or were the rendezvous cancelled totally
>as a consequence of the fuel shortage due to inefficient impulse
>thrusters? ...

This decision will not be made for a while.  JPL wants to see how Galileo
actually performs in space.  The pre-flight uncertainties about things like
attitude-control performance are enough to affect the decision.  Certainly
if things go poorly, the mission will have to be trimmed a bit.
--
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry [e-mail]

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

Date: 26 Oct 89 06:41:49 GMT
From: mailrus!jarvis.csri.toronto.edu!csri.toronto.edu![e-mail]  (Raymond Blaak)
Subject: Re: "Terraforming", so-called...

[e-mail] (Wm E Davidsen Jr) writes:
>  The stars: hell, let's just find one with some nice planets and move
>there. Leave terraforming to fiction.


It has occurred to me that the idea of restricting ourselves to just
living on planets really limits our options in terms of future expansion into
space. Good planets are probably very rare!

Humanity could exist in a lot more places if other star systems were rated in
terms of the raw materials found (hydrogen, oxygen, carbon, etc.) rather than
in terms of habitable planets. We can BUILD our own environments!

I have often come across the idea of reaching the stars by some sort of "Ark"
ship, in which generations of colonists live and die, until finally the
descendants reach the destination star system after hundreds (thousands?) of
years to colonize some planet. Well, if such environments could be built and
be lived in for that long, then maybe the planet is unnecessary.


Ray Blaak

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

Date: 25 Oct 89 22:11:00 GMT
From: visdc![e-mail]  (John E Van Deusen III)
Subject: Re: Asteroids as weapons of mass destruction

In article <[e-mail]> [e-mail]
(Henry Spencer) writes:
> ...
> [ concerning the energy required to deflect an asteroid into a long-
> delayed earth collision ]
>
> Potentially almost zero.  Potentially zero, in fact, given that there
> is a significant chance of a natural impact if you wait long enough.
> Humans do tend to be impatient, however... :-)

What an ironic doomsday weapon!  In contrast to our current implements
that can only manifest destruction as a futile act of momentary madness,
this would allow for a reasoned revenge upon an enemy by destroying his
progeny.  An analogy might be the destruction of modern Israel as a
result of a long-forgotten dispute, (some communications problem), that
arose once upon a time in Babylonia.  It is really destabilizing, much
as in the days before nuclear weapons, because the old men who start the
wars don't run much risk of dying in them.  The irony comes from the
inevitability that we humans, soon after destroying ourselves, would
surely band together in a desperate attempt to prevent the realization
of our demise.  It might become our finest hour.
--
John E Van Deusen III, PO Box 9283, Boise, ID  83707, [phone]

uunet!visdc!jiii

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

Date: Wed, 25 Oct 89 22:57:46 PST
From: Peter Scott <[e-mail]>
Subject: Re: Final Frontier demise?
X-Vms-Mail-To: EXOS%"[e-mail]"

[e-mail]  (Mike Marshall) writes:

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

Date: 26 Oct 89 01:38:36 GMT
From: [e-mail]  (Terry Hancock)
Subject: Re: Radar astronomy

In article <[e-mail]> [e-mail] (John Roberts) writes:
>
>
>As I was reading about advances in "radar astronomy" of the planets and moons
>of the solar system, an idea occurred to me, and I would like to know if
>anybody is working on it:
>
>A recent article describes radar probes of Saturn's moon Titan. The Goldstone
>antenna was used as a transmitter, and the Very Large Array was used as a
>receiver. It makes sense to use an array of receivers, so that the exact

>I'm not sure, but I think that similar control
>of the phased array can be used to transmit in a specific direction.
>
>                            John Roberts
>                            [e-mail]

    This is called radio interferometry, and it's done all the time.
I'm surprised you don't know that, since you mentioned the VLA, since it
works entirely on this principle itself.  Doing this with telescopes based
all over the world is called Very Long Baseline Interferometry (VLBI),
and has been quite successful.
    Of course, this is mostly used for looking at deep space radio
*sources*, and radar is a slightly different matter.  I'm not sure if
interferometry is being used for planetary radar, although with the
resolution that I've seen on planetary radar images, it seems likely to
me.



**********************************
Terry Hancock
[e-mail]
**********************************

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

End of SPACE Digest V10 #182
*******************