Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_0/V10_035.TXT

Internet Message Format | 1991-07-08 | 17KB

Return-path: <[e-mail]>
X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson
Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr1/ota/space/[e-mail] (->+dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl) (->ota+space.digests)
          ID </afs/andrew.cmu.edu/usr1/ota/Mailbox/QZ3lt1600jaS81pE5=>;
          Wed, 13 Sep 89 23:42:59 -0400 (EDT)
Message-ID: <[e-mail]>
Reply-To: [e-mail]
From: [e-mail]
To: [e-mail]
Date: Wed, 13 Sep 89 23:42:21 -0400 (EDT)
Subject: SPACE Digest V10 #35

SPACE Digest                                      Volume 10 : Issue 35

Today's Topics:
    Re: NASA designates 17 space grant colleges/consortia
             Re: Magnum snoopsat
            Re: Selling moon rocks
               Re: Pluto fly-by
             Stellifying Jupiter.
    Re: Exotic Thrusters (was Re: Where the hell are electric...)
      Re: Was Voyager another damaging Apollo one-shot?
               Re: Stellifying Jupiter.
             Re: Exotic Thrusters
         Re: Voyager's Interstellar Itinerary
          Mars Map [was: Re: Mars "face" image data]
     Re: Galileo Jovian atmospheric probe -- is it sterilized???
----------------------------------------------------------------------

Date: 1 Sep 89 17:07:17 GMT
From: frooz![e-mail]  (Steve Willner)
Subject: Re: NASA designates 17 space grant colleges/consortia

In NASA press release, article <[e-mail]>, posted
by [e-mail] (Peter E. Yee):
[Thanks, Peter, for posting these.]

>      These Designated Space Grant Colleges/Consortia will receive
> funding for 5 years.  In fiscal year 1989 each designee will
> receive $75,000.  In subsequent years, the institutions will
> receive up to $225,000 per year ...

It sure says something about the state of educational funding that
administrators are willing to put together consortia of up to 17 (!)
institutions and submit (presumably lengthy) proposals for this amount
of money.
-------------------------------------------------------------------------
Steve Willner            Phone [phone]         Bitnet:   willner@cfa
60 Garden St.            FTS:      830-7123           UUCP:   willner@cfa
Cambridge, MA 02138 USA                 Internet: [e-mail]

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

Date: 1 Sep 89 15:29:06 GMT
From: sei![e-mail]  (Robert Firth)
Subject: Re: Magnum snoopsat

In article <[e-mail]> [e-mail] (Stacey Campbell) writes:

>A satellite in geosynchronous orbit over the European part of
>the Soviet Union...

... would be a real neat trick!  The southernmost point of the
European part of the USSR, the city of Batum on the East coast
of the Black Sea, is at 42 degrees North latitude.

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

Date: Fri, 1 Sep 89 09:22:05 PDT
From: [e-mail]
X-Vmsmail-To: SPAN::AMES::"[e-mail]"
Subject: Re: Selling moon rocks

    In a recent article, I said that Americans spent $17G on
entertainment last year.  I've since found that in fact, this figure (which
I heard on the radio) is good for movies and prerecorded music alone!
According to the US Commerce department, Americans spent $223G on all
leisure activities in 1987, not including expenditures on recreational
drugs (nor expenditures on counteracting their side effects).  This amounts
to an average of $185 per month per family.
    NASA's 1987 budget was about $10G in 1987, which comes to $8 per
month per family, or about $3 per person.  So next time somebody says we
should spend money on <insert worthy cause here> instead of space, give
them $3 and tell them to live it up.

----
"Drive Friendly or Die"            |         Dale M. Greer
  Proposed Texas License Plate Motto    |   Center for Space Sciences
              -- Anonymous    | University of Texas at Dallas
                    | UTSPAN::UTADNX::UTDSSA::GREER
The opinions are my own, and may or may not reflect those of my employer.

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

Date: 1 Sep 89 18:53:46 GMT
From: frooz![e-mail]  (Doug Mink, OIR)
Subject: Re: Pluto fly-by

On Monday, August 28, R.T. Mitchell of JPL gave a talk, "Interplanetary
Trajectory Design," at a conference I was attending in Pasadena.  He
described an assortment of interesting gravity assist maneuvers for getting
to a variety of places in the solar system ranging from solar impact to
a Pluto flyby.  While the trajectory the Pluto community has been talking
about takes 17 years, JPL has come up with Earth- and Jupiter-assisted
routes that take as little as 10 years.  The problem with fast trips is
that you zip through the system too fast to study anything for very long.
Some of my friends on the Voyager team expressed the feeling that it would
be OK to leave one planet unprobed for future generations to discover.  For
now, Triton will serve as a good analog for Pluto, being of similar size,
similar distance from the sun, and possessing a similar atmosphere with a
haze layer.

Doug Mink
Harvard-Smithsonian Center for Astrophysics
Cambridge, Massachusetts

Internet:  [e-mail]
BITNET:    mink@cfa
SPAN:      cfa::mink
Phone:     [phone]
FTS:       830-7408

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

Date: 2 Sep 89 00:31:16 GMT
From: wrksys.dec.com![e-mail]  (CUP/ASG, MLO5-2/G1 6A, 223-3283 01-Sep-1989 1428)
Subject: Stellifying Jupiter.


        In the October 1989 issue of ANALOG magazine, there is an article
    by Martyn J. Fogg entitled "Stellifying Jupiter" about speculation
    on turning the planet Jupiter into a star to aid in terraforming the
    the Jovian world's Galilean moons (Io, Europa, Ganymede, Callisto) -
    much as what occurred in author Arthur C. Clarke's book and film 2010 -
    only this project is to be done by our very distant descendants with
    highly advanced technologies rather than some superior alien force
    (though who knows who will be doing what in the far future).

        The basic plan calls for transporting a primordial collapsar
    (black hole) to Jupiter to be used in the process of "stellifying"
    the giant gas planet.  The project would last hundreds of millions
    of years, and one would have to take care not to either let Jupiter
    fizzle out or turn into a miniature supernova in the heart of our
    solar system.

        The article does make for an interesting thought experiment.

        Larry Klaes  [e-mail]
             or - ...!decwrl!wrksys.dec.com!klaes
                 or - [e-mail]

        EJASA Editor, Astronomical Society of the Atlantic

             N = R*fgfpneflfifaL

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

Date: 1 Sep 89 15:28:08 GMT
From: [e-mail]  (Terry Hancock)
Subject: Re: Exotic Thrusters (was Re: Where the hell are electric...)

In article <[e-mail]> [e-mail] (Neal Woodall) writes:
>
>Well, as someone has suggested already, maybe we can use the Soviet's Topaz
>reactor for the power....we have the thrusters, they have the reactor. and
>this might make a "winning combination".
>
    I doubt we'll get it anytime soon.  But I'm for it if we do.

>The Power Processing Unit.....don't know what this is, but it sounds as if
>it is the device that generates the electricity and then converts it to the
>correct volt/amp combination that keeps the thruster happy....is this right?
>
    The PPU is roughly what you say -- it generates a variety of
different voltages, varying from 15 V to 1000 V.  Different parts of the
thruster have to sit at different potentials, you see.  The PPU for the
30-cm is between 80% and 90% efficient -- but that still means that
300 W to 600 W has to be dissipated as heat.  Systems for dissipating
this heat are not strictly part of the PPU, but they make up a lot of
it.  I don't know if that accounts for the weight or not.

>>By the way, the source, (ION Propulsion for Spacecraft,
>>Publication of NASA Lewis Research Center 1977)
>
>
>Neal

    Hope this is helpful.



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

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

Date: 2 Sep 89 05:11:14 GMT
From: van-bc!ubc-cs!cheddar.cc.ubc.ca![e-mail]  (Laura Halliday)
Subject: Re: Was Voyager another damaging Apollo one-shot?


Don't forget that before Voyager, Triton had only been, at best, a point
of light in somebody's telescope. We had only vague notions about Titan.
And so on. Now they're places. Worlds. All different.

People who yawn with Apollo16itis sadden me. Have they no imagination? No
sense of wonder at the amazing things that Voyager and JPL have accomplished?
Or are they like the 1890's patent official who quit his job because
everything had already been invented?

The exploration of outer space hasn't even begun yet. Voyager was just a
teaser: a hint of things to come.

...laura

Addendum: THANK YOU JPL for the pictures you folks have made available on
the net. I snagged some of the GIF versions and they've gone down a storm
here...

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

Date: 2 Sep 89 05:00:12 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Stellifying Jupiter.

In article <[e-mail]> [e-mail] (CUP/ASG, MLO5-2/G1 6A, 223-3283  01-Sep-1989 1428) writes:
>        In the October 1989 issue of ANALOG magazine,

good old ANALOG with its unending string of accurate predictions :-)

>                                                     there is an article
>    by Martyn J. Fogg entitled "Stellifying Jupiter" about speculation
>    on turning the planet Jupiter into a star ...

>                           The project would last hundreds of millions
>    of years, and one would have to take care not to either let Jupiter
>    fizzle out or turn into a miniature supernova in the heart of our
>    solar system.

I assert that if we're still around in hundreds of millions of years,
we will not need to "terraform" four crummy Galilean moons.  Even if
we desperately did want to render them habitable, there have got to
be ways of doing it that take less than hundreds of millions of years.

I would also seriously question what kind of star you'd end up with, that
would be useful as a power plant yet safe to orbit at Galilean distances.
Places like Io are already radiation and tidal hell due to resonance and
electromagnetic effects just from the cold gasball.  Stars have ferocious
fields.

The problem with the "science fact" in ANALOG is that they all read SF
all the time and it skews their standards.  Sometimes the only difference
is having diagrams instead of macho mercenary portraits.
--
Annex Canada now!  We need the room,    \)    Tom Neff
    and who's going to stop us.        (\    [e-mail]

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

Date: 2 Sep 89 01:21:13 GMT
From: [e-mail]  (Terry Hancock)
Subject: Re: Exotic Thrusters

In article <[e-mail]> [e-mail] (Paul Dietz) writes:
>>[MagnetoPlasmaDynamic (MPD) Thrusters have a short]
>>lifespan: the components corroded or something. Sorry I don't have
>>any references on this. Might someone else (specifically, Paul
>>Dietz of `cs.rochester.edu'?)
>
>I hope you saw the note I posted with the references (Progress in
>Astro. and Aero. Vol 79).
>
>I don't think corrosion is what would occur, since an MPD thruster
>would use argon as a propellant, and argon is inert.  You would get
>erosion on the electrodes, since they would carry a large current
>(kiloamps).  According to the ~8 year old reference I have, they were
>gearing up at Princeton qto do experiments to measure the "extremely
>low ablation rates".
>
    "Or something" -- actually in my lexicon, corrosion is pretty
general.  Has the more exact definition of *chemical* breakdown I
gather?

>I should note that ion engines also have erosion problems, which are
>severe because a thin metal mesh (the accelerating grid) is placed in
>the ion flow.  Mercury ions sputter metal atoms off this grid.
>According to my reference, this limits engine lifetime to ~15,000
>hours, or about 1.7 years.  The electrodes in an MPD thruster would be
>thick rods and cylinders made of solid tungsten or copper, which seem
>much more robust to me.
>
>    Paul F. Dietz
>    [e-mail]

    More robust, probably, but they'd have to be.  The voltage may
be similarly high, but I suspect that current is what determines the
erosion rate.  After all, you're moving a lot of electrons through that
system.  Admittedly, the ions aren't too friendly, either.
    Also, of course, the MPD sounds like it must be a lot heavier.

    This brings up an idea I had.  You say that this process limits
the engine lifetime -- that's not accurate.  It really limits the grid
lifetime, and of course, the grid weighs only a 100 g or so (I'm just
guessing, but I think the grids are really lighter than that).  At that
mass, you could carry a hundred of them, and get 1,500,000 hours or
170 years use out of them.  Of course, you have to figure out an automatic
installation system.

    On the other hand, if you look at the specs I posted earlier,
you'll see that the whole thruster weighs only 8.8 kg -- it's the
PPU and other junk that makes up most of the weight (~58 kg).  You
could just carry a spare thruster to use when the first one fails,
but only 1 PPU.   Thus you get a 76 kg thruster (30-cm) with a
lifetime of 30,000 hours instead of a 67 kg thruster with only
15,000 hours.  Anybody have ideas about that?

    By the way, Paul Dietz, I'm not knocking MPD's -- on the contrary,
they sound fascinating.  I just wanted to suggest how to overcome the
lifetime problem on electrostatic drives (ESD's? :-)).






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

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

Date: 2 Sep 89 03:58:11 GMT
From: agate!shelby!portia!hanauma![e-mail]  (Joe Dellinger)
Subject: Re: Voyager's Interstellar Itinerary

In article <[e-mail]> [e-mail] writes:
>296036       Closest approach to Sirius - 4.32 ly away.
>             14.64 ly from the Sun.
>
>        Personally, I wouldn't trust the numbers past about 60000 years -
>there are still too many unknown possibilities for gravitational influences.
>
I wouldn't trust numbers past 1000 years myself. I'll make a 50$ bet that
within 600 years Voyager will be proudly on display in the Smithsonian, as
a monument to the fading days of the WWII era of world history. (I'm willing
to make a 50$ bet because I know 50$ by then will be the equivalent of 2 cents
now.)
\    /\    /\    /\/\/\/\/\/\/\.-.-.-.-.......___________
 \  /  \  /  \  /Dept of Geophysics, Stanford University \/\/\.-.-....___
  \/    \/    \/Joe Dellinger [e-mail]  apple!hanauma!joe\/\.-._

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

Date: 2 Sep 89 07:50:36 GMT
From: bbn.com![e-mail]  (Nichael Cramer)
Subject: Mars Map [was: Re: Mars "face" image data]

In article <[e-mail]> [e-mail] (Henry Melton) writes:
>...
>Now if I can only get the rest of the planet to play with ....

While it's not quite the same, the US Geological Survey has a very nice
topological map of Mars:

Atlas of Mars
M 25M 3 RMC
1976
I-961

They cost about $8(?) when I got mine about 3 yrs ago.

Enjoy
NICHAEL

|       Nichael Lynn Cramer    |           UNIX??!?           |
|        --  [e-mail]   | Wow!! And they say I'M stuck |
|        --  [e-mail]   |in the sixties!  -- Wavy Gravy|

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

Date: 1 Sep 89 21:53:26 GMT
From: sco![e-mail]  (Evan A.C. Hunt)
Subject: Re: Galileo Jovian atmospheric probe -- is it sterilized???

[e-mail] (Paul Dietz):
>It's a question of perceived risk.  It is believed that the risk is very
>small.  If one asks that the risk be zero, then one is a technophobe --
>and, IMHO, a fool.

    How difficult would it be at this point to sterilize the atmosphere
probe?  I have difficulty believing that something designed to withstand
Jovian conditions would be damaged if we ran hot steam over it for a few
hours.  I agree that the risk of contaminating Jupiter is small, but if
the cost to make it even smaller is negligible, then I think it's much
more foolish not to try.

--
    Evan A.C. Hunt            [e-mail]
    The Santa Cruz Operation, Inc.    uunet!sco!evanh
    [phone]            [e-mail]

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

End of SPACE Digest V10 #35
*******************