Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_0/V13_028.TXT

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Subject: SPACE Digest V13 #028

SPACE Digest                                      Volume 13 : Issue 28

Today's Topics:
         NASA Headline News for 01/04/91 (Forwarded)
              room avail to see eclipse
            Re: Chiron and asteroid belts
           Building a sundial, position of the sun
             Re: Bussard ramjet question
            Satellite description
             Re: Interstellar Light Sails
              Re: Interplanetary travel
               Re: Interstellar Travel

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription requests,
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Date: 4 Jan 91 22:22:24 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Organization: NASA Ames Research Center, Moffett Field, CA
Subject: NASA Headline News for 01/04/91 (Forwarded)
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             Headline News
Internal Communications Branch (P-2) NASA Headquarters

  Friday, January 4, 1991    Audio Service: 202 / 755-1788

This is NASA Headline News for Friday, January 4, 1991

NASA  has announced that it would jointly develop a spacecraft with the
European Space Agency to study the planet Saturn, its moons, rings,
atmosphere and magnetosphere.  The formal agreement was recently signed
by Administrator Truly and ESA Director-General Jean-Marie Luton.

Named after the 17th century astronomer, Jean Dominique Cassini, the
probe will explore the Saturnian system with a planetary orbiter
provided by NASA and an ESA-provided Titan moon-orbiter.  The Saturnian
mission is expected to last for at least eleven years, seven of which
will be required for the journey to the outer planet.  Enroute, Cassini
will make asteroid observations and a Jupiter fly-by.  NASA expects to
launch the Cassini spacecraft aboard a Titan IV/Centaur booster in
April 1996.

* * * * * * * * * * * * * *

Artificial auroras may be created in January night skies  when NASA
conducts experiments releasing metallic vapors from the Combined
Release and Radiation Effects Satellite.  The joint NASA/USAF project
seeks to understand the processes which cause auroras by using
artificial charged-particle clouds to induce them. The release of the
barium and lithium vapors into the Earth's magnetosphere will have no
adverse environmental effect, and is expected to be visible in the
western hemisphere.

Scientists are studying auroral effects, which not only produce
brilliant natural displays, but affect high frequency communications,
power systems, and sensitive terrestrial and space instruments.

  * * * * * * * * * * * * * * * *

Kennedy Space Center workers installed the Forward Reaction Control
System on the Space Shuttle Discovery last night, and an interface test
of the system is planned for tomorrow.  Discovery is being prepared for
rollover to the Vehicle Assembly Building at the end of this month.
The orbiter Atlantis is powered up today for routine tests, and new
general purpose computers are being installed.  In the VAB, Columbia's
tile system is being waterproofed.  Technicians removed sleep stations
from the orbiter crew cabin yesterday.  Stacking of the STS-37
(Atlantis) Solid Rocket Boosters continues, and the new 17-inch liquid
hydrogen disconnect is being positioned on the External tank.



(No scheduled television programming through Monday)  This report is
filed daily, Monday through Friday, at 12:00 pm, EST.  It is a service
of Internal Communications Branch at NASA Headquarters.  Contact:
CREDMOND on NASAmail or at 202/453-8425.


NASA Select TV:  Satcom F2R, Transponder 13, C-Band, 72 degrees West
Longitude, Audio 6.8, Frequency 3960 MHz.

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Date: 4 Jan 91 18:29:56 GMT
From: uoft02.utoledo.edu!desire.wright.edu![e-mail]
Organization: University Computing Services, Wright State University
Subject: room avail to see eclipse
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 Going to the eclipse in Mexico this July and need someplace to stay?

 I have an extra space or two to fill in my hotel room in Puerto Vallarta
 starting on the night of Thursday 7/4/91 and ending on the night of
 Friday 7/12/91.

 If interested email to this address or call 1-513-435-4558 between
 8:00am and 05:00pm EST and just ask for Jack Frillman.

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Date: 2 Jan 91 02:46:22 GMT
From: ogicse!intelhf!agora![e-mail]  (Edward Fitzgerald)
Organization: Open Communications Forum
Subject: Re: Chiron and asteroid belts
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This reminds me...Members of a local BBS asked a question I am also interested
in. Are there any plans to have the Hubble look for/at any of our asteroids? It
would seem like the perfect device to finally get a good look at them.

Suze Hammond

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Date: 4 Jan 91 19:05:01 GMT
From: njin!njitgw!hertz.njit.edu![e-mail]  (ken ng cccc)
Organization: New Jersey Institute of Technology, Newark, N.J.
Subject: Building a sundial, position of the sun
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Please pardon the cross-posting, I'm not sure which newsgroup this request
belongs to.  I have recently moved into a new office with a southern view.
I would like to put a small mirrow on the window to reflect the sun up at
the ceiling where I will have placed a sundial calbrated by time of day
and day of year.  My problem is, is there any way of doing this besides
marking it every day of the year?  Given the time, my longitude, lattitude,
and day of year, does anyone know a way to compute where the sun will be
in the sky?  Has anyone else tried something this nutty?

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Date: 30 Dec 90 22:49:18 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!censor!geac!torsqnt!lethe!telly!moore!eastern!egsgate![e-mail]  (Maury Markowitz)
Organization: EGS/Philo BBS Gateway, Toronto [phone]
Subject: Re: Bussard ramjet question
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>>OK, I was thinking about Bussard ramjets the other day (after reading
>>entirely too much science fiction) and got to wondering:  How do
>>you decelerate with a Bussard ramjet? ...
>You're going to have to decelerate the incoming gas essentially to
>a halt to hang onto it long enough to fuse it, unless you've got a
>truly remarkably rapid fusion reaction going somehow.  That being
>the case, there is no reason why you can't point the exhaust jet
>and the ramscoop in the same direction rather than in opposite
>directions.

  The more common suggestion as seen in JBIS is to hang a large "shield"
behind the craft, turn off the fusion, and let the incoming particle
stream reflect off the shield.  An energy-limited system has been
investigated in several papers, try...

G. L. Matloff and A. J. Fennelly, "Interstellar Applications and Limitations
of Several Electrostatic/Electromagnetic Ion Collection Techniques",
JBIS 30 (1977):213-222

N. H. Langston, "The Erosion of Interstellar Drag Screens", JBIS 26 (1973):
481-484

C. Powell, "Flight Dynamics of the Ram-Augmented Interstellar Rocket",
JBIS 28 (1975):553-562

A. R. Martin, "The Effects of Drag on Relativistic Spacefight", JBIS 25
(1972):643-652

  Hope that helps.

                                                   Maury



--
EGSGate Fidonet Gateway, Toronto (egsgate.fidonet.org)
...!{uunet, moore, lsuc}!eastern!egsgate

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Date: Fri, 4 Jan 91 13:39:19 PST
From: [e-mail] (Troy T. Pummill)
To: [e-mail]
Subject: Satellite description


Netlanders,

Now that I have copies of orbital data from T.S. Kelso and T. Molzcan,
where can I find a file that describes the different satellites and
their functions.....

thanks...troy (Troy)

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|  Mountain View, CA  94043    |  The preceding drivel is entirely my own! |
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Date: 4 Jan 91 22:40:57 GMT
From: zephyr.ens.tek.com!tektronix!sequent!crg5![e-mail]  (Nick Szabo)
Organization: Sequent Computer Systems, Inc
Subject: Re: Interstellar Light Sails
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In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>[Forward's] lightsails in particular showed up in serious papers before
>he used them in his fiction.  If you can build the laser system
>on the necessary colossal scale, laser sails are workable.

What is the spread of a laser over interstellar, or even interplanetary
distances?  Last I heard from the deep-space laser communications people,
there is large dispersion over even interplanetary distances (alas I don't
have figures handy).  Transmitting power around the solar system via laser
could be quite useful to future space industry, if it is feasible.



--
Nick Szabo            [e-mail]
"If you want oil, drill lots of wells" -- J. Paul Getty
The above opinions are my own and not related to those of any
organization I may be affiliated with.

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Date: Fri, 4 Jan 91 21:14:42 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Re: Interplanetary travel


>Date: 24 Dec 90 20:40:16 GMT
>From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!cunews!cognos!geovision![e-mail]  (Gord Deinstadt)
>Organization: GeoVision Corp., Ottawa, Ontario
>Subject: Re: Interstellar travel

>Fusion engines are just the thing for travelling about in the solar
>system.  Since the ideal reaction mass is 4 times the (payload+
                ------------------------------------------------
>structure) mass, there is no point in having a higher-density fuel.
 ---------------
>You just have to carry more reaction mass to compensate for the
>reduction in mass of the fuel.  Consequently, for efficient (minimum-
>energy) operation, fusion is just as good as antimatter, provided
>the fusion reactor can be made light enough.

>Gord Deinstadt  [e-mail]

I don't understand why that should be considered an ideal ratio. By the
classic equations, this should allow a total change in velocity of about
1.6 times the exhaust velocity, but why is that a particularly good number?
     John Roberts
     [e-mail]

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Date: 5 Jan 91 01:33:43 GMT
From: mindcraft.com![e-mail]  (Ronnie Kon)
Subject: Re: Interstellar Travel

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Tony Hamilton, WF1-81, x48142) writes:
>
>given that the energy requirements go as the square of velocity.  (Energy
>is the dominant problem of starflight.)

    It's also the dominant problem of interstellar communications.  Even
with a really bitching Buck-Rogers 0-degree-spread laser, it's going to be
awfully hard to punch a beam all the way back to Earth.  We're having enough
trouble just receiving Voyager's transmissions, and it's not even out of the
solar system.

    Perhaps it could go into a parking orbit around the star (doing a hell
of a decelleration from .2C to orbital velocity) and absorb solar energy to
power it.  The beam would then, however, have to be separated from the
overwhelming energy from the very close, and very bright, star.

    Perhaps it can do a flyby, and do a 180 turn through the gravity well,
and return to us.  Probably about as likely as an interplanetary mission within
the next couple of centuries.

    Pity.

                Ronnie
--
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Ronnie B. Kon                    |  "I don't know about your brain, but
[e-mail]       |  mine is really bossy."
...!{decwrl,ames}!mindcrf!ronnie |               -- Laurie Anderson

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End of SPACE Digest V13 #028
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