Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_0/V10_009.TXT

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Subject: SPACE Digest V10 #9

SPACE Digest                                       Volume 10 : Issue 9

Today's Topics:
                 Re: Question
           Re: RTG's and nuclear reactors.
            Re: Voyager Color Pics
      Amusing comment from 8/26 Voyager press conference
           Re: RTG's and nuclear reactors.
             Re: Neptune on the Boobtube
             Re: Message on Mars
             Re: Message on Mars
                 ICE (ISEE-3)
               Re: Voyager 1 Trajectory
         Re: Economies of Scale in Launchers
----------------------------------------------------------------------

Date: 26 Aug 89 04:41:40 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Question

In article <[e-mail]> [e-mail] (rds) writes:
>         Would a clock (earth time) placed on voyager
>         12 years ago be presently running at a different time
>         compared to current earth time due to relativistic
>         effects?

A very, very little bit.  The crucial issues are velocity (special
relativity) and gravitational fields (general relativity), both of
which affect clocks.  Voyager is moving (mostly) at fairly modest
speeds, and is also in (mostly) somewhat weaker gravitational fields
than clocks here.  The effects ought to be detectable but would not
be dramatic.
--
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: 26 Aug 89 04:49:34 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: RTG's and nuclear reactors.

In article <[e-mail]> [e-mail] (Rikhit Arora) writes:
>In response to my original queries regarding Galileo's RTG's, Henry
>mentioned that one should get rid of RTG's altogether and switch to
>nuclear reactors.  Well, what exactly is an RTG then?  It *is* called
>a Radioisotope Thermoelectric Generator...

An RTG is an isotope capsule plus thermocouples.  Normal radioactive
decay in the isotope keeps the capsule, and one end of the thermocouples,
warm.  Radiator fins keep the other end of the thermocouples cold.  The
thermocouples respond by generating modest amounts of electricity.  It's
not a terribly efficient system, but it has the virtue of being completely
without moving parts.  The usual isotope is Plutonium 238, which has a
fairly short half-life and decays by alpha emission (which is easily
shielded against, a desirable feature when sensitive instruments are
along for the ride).  (This is not the bomb isotope, that's Pu-239.)

>... And what technical difficulty
>prevents NASA from using a real nuclear reactor for these deep space
>probes?

Mainly, a reactor is a good deal more complicated and generally heavier.
One would think about using one for bigger probes with higher power
requirements.  Development of a suitable reactor would be expensive.
(Although the Soviets will sell you one...!)
--
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: 26 Aug 89 06:57:08 GMT
From: [e-mail]  (David Palmer)
Subject: Re: Voyager Color Pics

In article <[e-mail]> [e-mail] (Steve) writes:
>
>Question: while watching the PBS "Neptune All Night" broadcast, all
>they showed were black and white images.  Are there separate RGB
>images transmitted of for each frame sent back, or just some pre-
>designated frames.  Also, I've heard it takes 90 seconds to take
>a picture, or is it 90 seconds to *transmit* the picture? Can anyone
>knowledgable clarify - its so hard to get the facts from any TV news
>source.  Thanks,

There are separate black and white frames shot through various filters
(UV, green, blue, orange, two methane bands, etc.)  The filter name is
given by the first column, second line, at the end of the 'word',
below the picture.

I believe that each frame takes 10 minutes to transmit.  It is 800x800 pixels
by 8 bits of intensity.

        David Palmer
        [e-mail]
        ...rutgers!cit-vax!tybalt.caltech.edu!palmer
    "Direct quotes don't have to be exact, or even accurate.  Truth is as
    irrelevant to a newspaper as it is to a court of law"
    - Judge Alarcon, 9th circuit court of appeals (paraphrased)

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

Date: 26 Aug 89 18:38:28 GMT
From: thorin!alanine.cs.unc.edu![e-mail]
Subject: Amusing comment from 8/26 Voyager press conference


    "The imaging team is moving from its ``instant science'' mode to a
     more leisurely ``fast science'' mode."
    - Dr. Bradford Smith, Voyager Imaging Team
--
    Jon Leech ([e-mail])    __@/
    SUSHIDO: the Way of the Tuna

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

Date: 26 Aug 89 21:46:33 GMT
From: thorin!alanine![e-mail]  (Jonathan Leech)
Subject: Re: RTG's and nuclear reactors.


    Several people have mentioned problems with the Galileo RTGs
having reduced power output due to the long launch delay, and there
being no way to replace them.  Where are the RTGs for CRAF and Cassini
supposed to come from, then, now that the missions are funded?    Is the
plant to be reopened?
--
    Jon Leech ([e-mail])    __@/
    ``I have a fair amount of faith in American free press; oppression
      continues to surface, but justice will always triumph as long as
      enough money can be supplied.'' - Reed Waller

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

Date: 25 Aug 89 19:53:15 GMT
From: asuvax!mcdphx!mcdchg!ddsw1!corpane![e-mail]  (John Sparks)
Subject: Re: Neptune on the Boobtube

In article <44600002@primerd> [e-mail] writes:
>
>WGBH in Boston, and several other PBS stations around the country will be
>broadcasting the whole night long on the evening of closest approach, 8/24-25.
>I think that this will be mostly "live" shots directly from Voyager, but
>I think they're also setting up phone lines for people to call in.  They'll
>probably have experts from JPL or the like commenting on what is being

Well I watched it. Just who were the dweebs that they had commenting? For the
most part they didn't know their head from their A**.

At one point a caller asked what will happen to Voyager, where will it go when
it leaves the system.

The answer was that in 8,000 years it will fly by Barnard's Star, in 20,000 or
so it will pass Proxima Centauri, and then the Oort cloud.

GACK!!! How bass-ackwards can you get?!!!

---
Late in the morning they were talking about the pictures and someone mentioned
that there was a Nasa BBS that you could download photos of neptune from. Does
anyone know anything about this? The number?

--
John Sparks   |  {rutgers|uunet}!ukma!corpane!sparks | D.I.S.K. 24hrs 1200bps
|||||||||||||||          [e-mail]         | 502/968-5401 thru -5406
You are in a maze of twisty little passages, all alike.

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

Date: 27 Aug 89 01:59:08 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Message on Mars

In article <[e-mail]> [e-mail] (James P. Galasyn) writes:
>If Hoagland has shown nothing else, he has demonstrated convincingly that
>the Face at Cydonia is quite symmetrical.  He and Dr. Mark Carlotto of The
>Analytical Sciences Corp. have constructed a 3D computer model of the Face
>from two Viking orbiter photographs, 35A72 and 70A13.  When the model is
>rotated for observation from different viewing and illumination angles, no
>matter where you stand or where the sun is, it LOOKS artificial as hell.

Uh, this proves that the *model* looks artificial as hell regardless of
angles, and that the *model* is quite symmetrical.  It does not prove
that this is the only model which fits the Viking photographs, or that
the model corresponds to the Martian surface feature in question.
--
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: 23 Aug 89 16:57:18 GMT
From: ssc-vax!shuksan!tahoma![e-mail]  (James P. Galasyn)
Subject: Re: Message on Mars

In article <[e-mail]>, [e-mail] (William Baxter) writes:

> I have before me a post card which bears the profile of John F. Kennedy.
> The startling likeness is a rock formation on the island of Maui,
> Hawaii.

I bought an interesting book at a closeout sale, called _Simulacra_.  The
author has collected photographs of rocks, trees, lakes and other natural
structures that bore striking resemblances to human faces and such.  These
things are amazingly common, but virtually all the face structures observed
in rock formations are profiles. In the chapter "Rock Faces" the author
shows twenty-five photographs of "spontaneous" human heads from all over the
Earth, none of which is face-on.  Though the faces are often startlingly
anthropomorphic, there is not a single occurrence of bilateral symmetry.

Interestingly, human faces occur spontaneously on living organisms, and
these are very symmetrical.  The chrysali of many butterflies and well as
their wings, the carapaces of English and Japanese crabs, and the abdomens
of many spiders have humaniform visages molded into their markings and/or
morpohology.

If Hoagland has shown nothing else, he has demonstrated convincingly that
the Face at Cydonia is quite symmetrical.  He and Dr. Mark Carlotto of The
Analytical Sciences Corp. have constructed a 3D computer model of the Face
from two Viking orbiter photographs, 35A72 and 70A13.  When the model is
rotated for observation from different viewing and illumination angles, no
matter where you stand or where the sun is, it LOOKS artificial as hell.
Whether it is...


                  .
    DEATH       .  ..                    Set the controls
              .     . .                  for the heart of the sun
      .     .        .  .                                 - Floyd
    .  .. .           .   .   .
  .     . .            .    .  ..
.        .  .           .     . . .

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

Date: 26 Aug 89 16:50:36 GMT
From: dftsrv!drax![e-mail]  (Loren (Buck) Buchanan)
Subject: ICE (ISEE-3)

In article <[e-mail]> [e-mail] (Henry Spencer)
writes:
>In article <[e-mail]> [e-mail] (Gregory Harrison) writes:
>> ...There was, and may still be, a satellite placed at the libration point
    [stuff deleted]

>This is a little garbled.  ISEE-3, the third International Sun-Earth Explorer,
    [stuff deleted]

>Getting ICE out to G-Z was quite a trick, involving an elaborate series of
>maneuvers, several lunar flybys, and orbits that look truly bizarre.  But
>ISEE-3 was built for that job.  However, late in its life it was rechristened
>ICE, the International Comet Explorer, and was redirected to an encounter
>with comet Giacobini-Zinner.  This was the best the US could do for a comet
>mission, all attempts at funding a US Halley mission having failed.  ICE's
>instruments were designed for solar-physics work, but could return enough
>useful data about the comet's tail that the diversion was thought worthwhile.
>it did all work, and ICE made the very first comet encounter, some months
>before the Soviet/Japanese/European flotilla of custom-built probes arrived
>at Halley.

It took Goddard Space Flight Center and Computer Sciences Corporation about
a year to do all of the analysis of moving a somewhat self propelled
particle through a three body space.  The final simulation run took three
months of computer time.  ISEE-3 went through 4 Earth and 5 Moon flybys
to fling it out on its intercept path.  Its last flyby of the moon was about
75 miles above the surface.  Part of its trajectory made a figure 8 (as
viewed relative to the Sun-Earth line) and extended about 700,000 miles into
the Earths geomagnetic tail.

ISEE-3 was the first spacecraft to prove that libration points (even the
unstable ones) are useful (as opposed to just being mathematically
interesting) and was the first spacecraft to do a study of the geomagnetic
tail of the Earth at any significant distance from Earth.  After it
made its closest approach to the moon it was renamed ICE, becoming the
first on-the-fly recycled spacecraft.  It is still operational and last I
heard its data rate is down to 100 bits per second.  If all goes right
it will still be operational in 2013, and will still have enough fuel on
board to set itself up for an Earth-Moon capture.

It is rumored that the Air and Space Museum has already put in a request
for it.  If it does get displayed, I would like to see some of the
PDP-11/xx equipment that supported it for 35+ years also displayed.  I
would be ecstatic if they were to recreate the control room as it existed
for the G-Z encounter (this would include an original IBM-PC 256K with an
AST memory board, a Conographic color card, and my software running on it).

The cost of converting ISEE-3 to ICE with support through the intercept was
about $3 million.  We owe it all to Robert Farquhar, who requested that
ISEE-3 be given as much fuel as possible, (which he got), and other extras
(which he did not get) when the initial design work was being done.  In
1982 Farquhar convinced the project scientists to allow ISEE-3 to be taken
out of its halo orbit for an excursion into the Earths geomagnetic tail,
but they insisted that ISEE-3 be returned to its halo orbit (no data, no
funding).  Farquhar through persistence, repeated negotiations, dealing
with bureaucratic red tape, and the occasional leaked story to the press,
got approval in October of 1982 to intercept G-Z.

Loren "Buck" Buchanan | internet: [e-mail] | standard disclaimer
CSC, 1100 West St.    | uucp: ...!ames!dftsrv!drax!buck   | "By the horns of a
Laurel, MD 20707      | phonenet: [phone] or 9898  | sky demon..."

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

Date: 27 Aug 89 02:59:53 GMT
From: zephyr.ens.tek.com!wrgate!teklds!mrloog![e-mail]  (Dan Tilque;6291545;92-101;OPUS_SW;)
Subject: Re: Voyager 1 Trajectory

Michael Richmond writes:
>
>   Oh, and is it fly-by or flyby or fly by?

Flyby.  The plural is flybys.  They (the singular and plural) are
probably the newest words in English without an 'a', 'e', 'i', 'o', or
'u'.

Interesting that Merriam-Webster's Ninth New Collegiate Dictionary
gives the year of origin as 1953.  Evidently, it was first used in
aviation.

---
Dan Tilque    --    [e-mail]

P.S. Followups to rec.games.trivia.

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

Date: 25 Aug 89 22:45:08 GMT
From: hpda!hpcuhb!hpcllla!hpclove![e-mail]  (Bob Campbell)
Subject: Re: Economies of Scale in Launchers

> Nope, high molecular weigth exhaust is better in a high pressure
> environment.  That is why there are solid fuel strap ons on so many
> boosters. In a vacuum you want the lowest possible weight exhaust.
>
>        Bob P.

Are we confusing high thrust with efficiency?

If I remember correctly (let me know if I am mistaken) . . .

Lower molecular weight of combustion products gives a higer efficiency.

If mass flow rate increases more than efficiency decreases, you get
higher thrust.

Pressure ratio determines the optimum expansion ratio of the nozzle.

So hydrogen is more efficient, but it may be easier to design a high
thrust engine/motor with different fuels.
--------------------------------------------------------------------------
Bob Campbell                Some times I wish that I could stop you from
[e-mail]        talking, when I hear the silly things you say.
Hewlett Packard                                    - Elvis Costello

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

End of SPACE Digest V10 #9
*******************