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Date: Thu, 31 Aug 89 05:18:01 -0400 (EDT)
Subject: SPACE Digest V10 #8

SPACE Digest                                       Volume 10 : Issue 8

Today's Topics:
    Anyone else see the Neptunian Vaxen? (Forwarded from Info-Vax)
             Re: How is Voyager powered?
              Voyager, etc. info sources
              re message on Mars
                 Space Digest
              Re: Thanks to NASA and JPL
           Re: Analysis of Martian "Face" Announced
               Re: Pluto fly-by
                Rings
               Re: Pluto fly-by
                Test message.
             Re: How is Voyager powered?
----------------------------------------------------------------------

Date: Fri, 25 Aug 89 10:17:59 PST
From: Peter Scott <[e-mail]>
Subject: Anyone else see the Neptunian Vaxen? (Forwarded from Info-Vax)
X-Vms-Mail-To: EXOS%"[e-mail]"

In INFO-VAX (comp.os.vms),
mailrus!sharkey!atanasoff!atanasoff.cs.iastate.edu![e-mail]
  (John Hascall) writes:

>    I was watching the NASA/JPL feed last night (wow!).  During one
>    "Voyager Update" they had a little counter showing the seconds
>    to closest approach:

>      00:00:05
>      00:00:04
>      00:00:03
>      00:00:02
>      00:00:01
>      17-NOV-1858           [= 0 in VAX system time units]
>
>    Oh well!  :-)

>John Hascall
>ISU Comp Center
>"Have your people call my people and we'll do lunch by the pool."  ;-)

Probably not programmed by the same folk that got the Triton Earth/Sun
occultation aiming on target.  (The parameters for the burn to achieve
that weren't uploaded until hours before target; the calculated time of
arrival had been jumping around all week.)

Peter Scott ([e-mail])

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

Date: 25 Aug 89 17:00:58 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Re: How is Voyager powered?

In article <[e-mail]> [e-mail] (Dennis M. O'Connor) writes:

>I believe Voyager uses one or more RTGs. RTGs contain a sub-critical
>mass of a fissionable material ( plutonium, I think ? ). The
>fission occuring causes the fuel to be hot.

No, the RTGs use Pu-238, which undergoes alpha decay, not fission.

>There is another kind of "no-moving-part" radioisotope generator.
>Don't know the name. It uses isotopes that emit charged particles
>( usually beta particles, I think. i.e. high-energy electrons ).

You may be thinking of the thermionic generator, where high
temperatures cause electrons to boil off certain metal surfaces.  The
electrons are certainly not high energy.

    Paul F. Dietz
    [e-mail]

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

Date: 25 Aug 89 15:47:46 GMT
From: att!mtuxo![e-mail]  (XT154-E.WENDLER)
Subject: Voyager, etc. info sources

.
.
.
Hi:

I'm interested in sources for technical information (navigational techniques,
etc.) about and photos from the Voyager missions as well as Pioneer.  Is JPL
the best place to go, and if so, is there an address/person to write?  Or
NASA, or a third party?

Please EMail responses--I'll summarize and post if I receive responses.

Thanks.

E.R. Wendler

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

Date: 25 Aug 89 19:04:00 GMT
From: apollo![e-mail]  (Peter Nelson)
Subject: re message on Mars


>                  The "Message of Cydonia":
>   First Communication from an Extraterrestrial Civilization?
>
>                                       By Richard C. Hoagland*
>
>                                          [Copyright (C) 1989
>                                           All Rights Reserved]
>
>                           Abstract

  Abstract from WHAT?   What is the paper that this is abstracted
  from?  IS there an actual paper?

>     The "face" and its surrounding "enigmatic landforms" appear
> to be a carefully layed out, highly-sophisticated, redundantly

  What 'enigmatic landforms?'?

> latitudes."  When examined by the authors, using published
> geodedic planetary maps from NASA and U.S Geological Survey
> sources, these latitudes are observed to be associated with a
> hitherto unknown planetary and stellar energy phenomenon --
> blatantly emerging at these specific latitudes

  And just what 'planetary and stellar' energy phenomenon
  might that be?  Radio waves?  Light?   X-rays?   Rock'n'roll
  music?  Orgasmotronic emissions?

  I dunno.  Sounds like ca-ca to me.

                                               ---Peter

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

Date: 24 Aug 89 19:40:53 GMT
From: mcsun!ukc!icdoc!syma![e-mail]  (Nick Watkins)
Subject: Space Digest

Could some kind soul tell me how to subscribe to Space Digest.
My feed is from Imperial College London, and I am reading UseNet with rn
if these are relevant.

Nick
--
Nick Watkins, Space & Plasma Physics Group, School of Mathematical
& Physical Sciences, Univ. of Sussex, Brighton, E.Sussex, BN1 9QH, ENGLAND
JANET: [e-mail]   BITNET: [e-mail]
Voice: [phone]

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

Date: 26 Aug 89 02:35:03 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Thanks to NASA and JPL

[ Followups directed to sci.space as this is not a shuttle issue. ]

Sentimental as John Bridge's proposal sounds, I think he is 100% right.
The Voyager team deserve medals at the White House, including posthumous
ones for the two deceased PI's.  Should we call the WH feedback number
and tell them this?  If so what is it? :-)
--
"We walked on the moon --    ((    Tom Neff
    you be polite"         ))     [e-mail]

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

Date: 25 Aug 89 02:30:48 GMT
From: jtsv16!geac!censor![e-mail]  (Jeff Hunter)
Subject: Re: Analysis of Martian "Face" Announced

[e-mail] (Jangling Neck Nipper) writes:
> In article <[e-mail]> [e-mail] (Ted Johnson) writes:
>
>    2.  The authors pulled in facts from all over to justify, amplify and
>    expand the significance they see.  Any theorist knows that, given enough
>    parameters, any observation can be explained.

> Could you perhaps point out the bits of the said article that are
> wrong, and could you say why they are wrong?  Are the `facts from all
> over' incorrect ones?  Is there anything inherently wrong with doing
> such a thing?

    I read an article Hoagland wrote for Analog several years ago.
He started with the picture of the face. It's pretty crude and
doesn't contain enough detail to draw many conclusions.

    So he started in on nearby objects. There's a hill (to the north?)
that is roughly like a five-sided pyramid. The faces are all about the same
length, and fairly flat. Hoagland pointed out the resemblance in proportion
to Da Vinci's famous sketch of man in a circle. He concluded that the
hill was a reinforcement of the face directing a message to mankind.
    I think it looks more like a giant Pontiac commercial.

    He then started in on a nearby ridge saying it was "obviously
artificial". There's a notch in the ridge, and if you line it up with
the eye of the "face" (or the main street of the "city", I forget) you
get a completely useless direction.
    But wait! If you calculate back in time as Mars' poles precess
the notch will eventually line up with some star or other on the
vernal equinox, or the summer solstice. Hoagland picks one of these
matches and thereby "proves" that the whole complex was created at some
ancient date.

    This goes on, but the pattern is the same. At the time I was
vividly reminded of the fact that you can reach *any* conclusion from
any data as long as you are allowed to use completely 'ad hoc' rules.

    It's too bad, because until then I had thought Hoagland was
an informed, if unconventional, commentator. After reading that article
I concluded that the Pauling effect had set in.

--
    -- my opinions --    [e-mail]

    Keep track of the current path, and use it naturally.
        Glenn Reid (Postscript Language Program Design)

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

Date: 26 Aug 89 02:58:32 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Pluto fly-by

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>>Would going via a third planet, perhaps prior to Jupiter, make the trip
>>any shorter?
>An intermediate stop before Jupiter will probably make it longer, although
>it may reduce fuel requirements a bit.

This is true for all MAJOR planets.  However one intermediate "stop" you can
make without undue penalty is to fly by a minor planet.  Galileo itself will
do this on the way to Jupiter, at great scientific benefit.

The interesting question is whether it's worth more to fly by the lone
remaining unseen planet, or to concentrate on orbiters for the seen ones.
--
"We walked on the moon --    ((    Tom Neff
    you be polite"         ))     [e-mail]

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

Date:         Fri, 25 Aug 89 09:27 CDT
From: Samitha Amarasiri <[e-mail]>
Subject:      Rings
To: <[e-mail]>


With the discovery of a ring on Neptune, it really looks like rings
on the outer planets on the solar system is becoming the rule
and not the exception. The two major differences between the
'outer' and inner planets are the temperature on them, and gravitational
pull by the sun. Could it be that either of these cause planets to
have rings on them? Could the asteriod belt be a ring that never
quite formed? Does this mean that Pluto will have a ring on it too?

Please excuse the barrage of questions, I was watching 'Neptune up all
night' and feel delerious with excitement.

--  Samitha Amarasiri.
______________________________________________________________________________
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------------------------------------------------------------------------------

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

Date: 25 Aug 89 18:37:10 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Pluto fly-by

In article <[e-mail]> [e-mail] (d. scott hess) writes:
>From: [e-mail]
>}I assume a fly-by of Jupiter would shorten the [Pluto] trip (with
>}respect to a direct flight), but by how much?

Infinite -- we cannot reach Pluto with current technology without a Jupiter
flyby.  I'd guess a Jupiter-Pluto mission at perhaps 7-8 years, but I don't
have real numbers handy.  Remember, also, that Jupiter will be in the right
place only about once every 8 years (its orbital period).

>}Would going
>}via a third planet, perhaps prior to Jupiter, make the trip
>}any shorter?

An intermediate stop before Jupiter will probably make it longer, although
it may reduce fuel requirements a bit.  Galileo will pay a considerable price
in transit time for its inner-planets gravity assists, since it means doing
several more orbits around the Sun to pass said planets.  Multi-planet
gravity assists shorten trips only when the planets are in *exactly* the
right places, and particularly in the outer solar system that isn't common;
the Voyager 2 Jupiter-Saturn-Uranus-Neptune window won't be open again for
a couple of centuries.

>... I've spent time trying to figure out
>exactly how gravity-assist works, and thus far, its beyond me...

I'll explain it briefly here, because it's relevant below.  (This one is
common enough that it probably ought to go in the frequently-asked-
questions list.)  Doing a pass by Jupiter will not change your speed
with respect to Jupiter, but it will change the direction of your motion.
This matters because Jupiter itself is moving.  Call Jupiter's orbital
velocity J (don't have the number handy).  If you approach Jupiter "from
the front" at 5 km/s relative to Jupiter, and do a tight hyperbola around
it so that the direction of motion with respect to Jupiter gets pretty
much reversed, then with respect to Jupiter you went in at 5 km/s and came
out at 5 km/s, but with respect to the *Sun* you went in at J-5 km/s and
came out at J+5 km/s.  Jupiter got slowed down infinitesimally in the
process.

>A little input I _can_ give is that Pluto is a helluva long ways out
>there...

Actually, right now it's at about the same distance as Neptune.  It's near
perihelion in its orbit, which is elliptical enough that an average distance
isn't too meaningful.

>... I think Pluto's [year] is
>somewhere over 230 years.  That's why we;d have to plan quite far ahead.

No, not really.  Something that moves that slowly can be treated as
motionless for rough planning purposes.

>... I suspect that the fastest way to get to pluto, albeit
>fairly weird, would be to do a gravity (un)assist around Jupiter, and
>the a gravity assist around the SUN...

Unfortunately this doesn't work, because the whole basis of gravity assist
is that the gravity-assist planet is moving with respect to your target.
You can't do it with the Sun.  (Although there are some related tricks.)
--
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry [e-mail]

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

Date: 25 Aug 89 22:24:38 GMT
From: wrksys.dec.com![e-mail]  (CUP/ASG, MLO5-2/G1 6A, 223-3283 25-Aug-1989 1321)
Subject: Test message.


    test message.

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

Date: 26 Aug 89 04:54:57 GMT
From: gem.mps.ohio-state.edu!csd4.csd.uwm.edu!mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: How is Voyager powered?

In article <[e-mail]> [e-mail] (Dennis M. O'Connor) writes:
>There is another kind of "no-moving-part" radioisotope generator.
>Don't know the name. It uses isotopes that emit charged particles
>( usually beta particles, I think. i.e. high-energy electrons ). The
>beta-emitter is in the middle of an exacuated sphere. The
>electrons are emmited by the beta-emitter and travel to the
>sphere wall. The sphere wall becomes negatively charged,
>and the central mass of beta-emitting material becomes
>positive. Connect wires to each and you have a battery.

Nuclear batteries have been built with this system, but the power output
is very low.  A related scheme with much better power output is to use
heat from an isotope or a reactor to "boil" electrons off a suitable
cathode.  This scheme, thermionic conversion, is used in the Topaz
high-power space reactor that the Soviets have flown experimentally
(and are now offering for sale).

>I've heard that high-power radarsats use actual reactors
>( with control rods, coolant, et cetera ), but have no idea
>how the heat is made into electricity.

The Soviet radarsats do indeed use reactors, mostly because they want to
operate at the lowest possible altitude (radar effectiveness requires
the shortest possible range) and with fairly high power output, and
the necessary solar arrays would produce too much air drag.  I think
their operational reactor uses thermocouples, just like the Voyager
RTGs.  Topaz may be intended as a replacement.
--
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry [e-mail]

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

End of SPACE Digest V10 #8
*******************