Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_0/V10_027.TXT

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Date: Thu,  7 Sep 89 03:17:05 -0400 (EDT)
Subject: SPACE Digest V10 #27

SPACE Digest                                      Volume 10 : Issue 27

Today's Topics:
         Re: Eugene Cernan talks for dollars
        Re: Voyager Pictures moved to another machine
               Electric Rockets
              NSS Hotline Update
               Re: Pluto fly-by
       Re: NASA Headline News for 08/30/89 (Forwarded)
          Solar sails (was Re: Pluto fly-by)
           Voyager Neptun/Triton  Encounter
               Re: Pluto fly-by
        Re: Post- Star Wars space habitability
----------------------------------------------------------------------

Date: 30 Aug 89 22:30:33 GMT
From: dptg!pegasus![e-mail]  (Paul S. R. Chisholm)
Subject: Re: Eugene Cernan talks for dollars

In article <[e-mail]>, [e-mail] writes:
> In article <[e-mail]>, [e-mail] (Steve Stein) writes:
> > Astronaut Captain Eugene Cernan . . . will be speaking . . .
> > Tickets are $12 for an adult, $10 for children.  Proceeds will
> > benefit the Acton Discovery Museums.
> > There will be a reception . . . tickets are . . . $35 apiece.

> Whew, steep prices! I am not surprised to see these costs when I
> realize it is for a "good cause".  However, Gene came and spoke to
> my High School Graduation Class in rural Calgary back in 1980.
> There was no charge. . . .

You have to differentiate what the *museum* is charging (it's
advertised as a fund raiser), and what Dr. Cernan is charging.  And
even if Dr. Cernan is getting paid, it's understandable.

I've helped organize a few space-related events at the New Jersey State
Museum.  We've had a couple of former mission specialists speak; they
seemed to like it, they did a great job, and their audiences ended up
both better informed and more enthusiastic about space exploration.

After a few years, one stopped volunteering; the other sadly informed
me that he had to charge a fee, normally such-and-such, for
appearances.  (He did last year's Spaceday at the museum for half
price.)  He wasn't (and isn't) greedy; he just had to cut back,
somehow, on the number of appearances he makes, and the easiest way to
separate the enthusiastic from the polite was to charge a speakers fee.
You would not *believe* the number of kids and parents who came up to
him and said, "I saw you when you came to my school."

(This past Spaceday, it seemed impossible to get *anyone* who flew,
unless you wanted to bring them to Houston, the Cape, or D.C.)

> Peter J. Russell, Bitnet: [e-mail] or [e-mail]

Paul S. R. Chisholm, AT&T Bell Laboratories
att!pegasus!psrc, [e-mail], AT&T Mail !psrchisholm
I'm not speaking for the company, I'm just speaking my mind.

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

Date: 30 Aug 89 07:29:57 GMT
From: agate!shelby!portia!hanauma![e-mail]  (Joe Dellinger)
Subject: Re: Voyager Pictures moved to another machine

In article <[e-mail]> [e-mail] (Tim Nelson) writes:
>O.K. it is nice that you are moving the pictures, but are they available
>anywhere to those of us who do not have access to FTP?
>(perhaps anonymous uucp?)

Sorry, I can't really get into mass e-mailing or uucp'ing the images;
ftp'ing them has been enough of a headache. However, there must be more
than a thousand copies of those images out there by now, so you might be
able to find some nearby machine that could get them to you. Even better,
is there anybody out there that already maintains an anonymous UUCP site,
and could easily add them to their archive? (If you are such a site and
willing to do this, but don't have ftp, send me e-mail.) The main image
file, containing what I thought were the 7 best pictures we digitized,
is a little over a megabyte. Is that too big for anonymous UUCP?
\    /\    /\    /\/\/\/\/\/\/\.-.-.-.-.......___________
 \  /  \  /  \  /Dept of Geophysics, Stanford University \/\/\.-.-....___
  \/    \/    \/Joe Dellinger [e-mail]  apple!hanauma!joe\/\.-._

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

Date: 30 Aug 89 13:59:02 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Electric Rockets

In article <[e-mail]> [e-mail] (Neal Woodall) writes:

>Please, some details!! Perhaps we can start a thread on "exotic" thrusters
>which would be good for the next generation of planetary probes. I am
>interested in any engine that allows continuous thrust for long periods of
>time, and will probably be of very high specific impulse. I have no info
>on the MPD engine you speak of......

One place you might look is in: Progess in Astronautics and Aeronautics,
Vol 79, Electric Propulsion and Its Application to Space Missions (Robert
Finke, ed.). AIAA, 1981.  This volume also has several articles on the
LeRC 30 cm Hg-ion engine, and the European RIT 35 Hg-ion engine, in
addition to a section on MPD thrusters.

MPD thrusters accelerate a plasma using Lorentz forces -- the force
exerted by a magnetic field on a perpendicular current.  In the
self-field MPD thruster, the magnetic field is generated by the
current pulse itself.  As I understand it, MPD thrusters are not as
efficient (maybe 50%) as ion engines (maybe 70-80%), but are much
smaller.  To operate at top efficiency, an MPD engine needs a lot of
power (~ 1 MW), so in low thrust applications they would operate with
low duty cycle -- the inefficiency in storing energy would be more
than made up for by the increased engine efficiency.

I seem to recall some more recent work on an "afterburner" for an MPD
engine that would use the plasma exhaust to heat a light gas, thereby
reducing the exhaust velocity and increasing thrust for a given
quantity of input power (references?).

An MPD engine might make sense in high power missions.  For example, a
nuclear-electric vehicle to Mars (8 MWe argon MPD thrusters; see AAS
86-172 in the 1986 NASA Mars Conference).  According to that article,
this NEP option would be quite favorable for a 15-year, 20 person Mars
base (in terms of expandable mass) in comparison with chemical
propulsion, even with propellant manufacture at the moons of Mars or
at Earth's moon, but would require much more powerful space reactors
than are currently available.

    Paul F. Dietz
    [e-mail]

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

Date: 30 Aug 89 15:01:00 GMT
From: cdp![e-mail]
Subject: NSS Hotline Update


This is the National Space Society's Space Hotline for MONDAY,
August 28.


The NSS was host to two successful fundraising events this last
week in California during the Voyager encounter with the planet
Neptune. NSS Board members hosted a reception on Friday, August
25 at the California Institute of Technology in which members of
the STAR TREK original series attended, as well as hundreds of
NSS members, and other special guests.

Saturday, August 26th saw a reception/buffet at the Paramount
Pictures studios on the set of ST:TNG. Nearly the entire cast of
ST:TNG, along with BOD Gene Roddenberry, BOG Hugh Downs, NSpC ex
Secy Mark Albrecht and family, NASA assoc admn for space science
applications Dr Lennard Fisk, Buzz Aldrin and a number of NSS
members and board members. The entire group got a chance to sit
in the Captain's seat on the bridge as well as to get beamed up!


The Voyager II spacecraft's encounter with Neptune has been a
spectacular success. Images and scientific data continue to pour
in and are analyzed. Among the findings are that there may be 5
rings encircling Neptune, the giant storm, in the great spot may
have winds up to 716 mph, and that active ice volcanoes may be
occuring on Triton. This would be 3rd body in solar system to
have active volcanoes

The first commercial rocket to carry a satellite into orbit was
launched from the Cape Sunday evening at 6:59pm. McDonnell
Douglas launched the three-stage Delta 187 booster with a 2,700
lb Marcopolo 1 satellite for the British Satellite Broadcasting
service.

The space shuttle Atlantis will be moved to launch pad 39B
beginning at 12:01 am EDT on Tuesday, 8/28.

This has been David Brandt for the NSS space hotline for Monday
august 28.

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

Date: Wed, 30 Aug 89 09:34:42 PDT
From: Peter Scott <[e-mail]>
Subject: Re: Pluto fly-by

[e-mail] (d. scott hess) writes:

> One proposal I've heard for
>light-sail launching says that the best way to launch (without large
>moon or space based lasers) would be to put it on an asteroid, and drop
>it into a cometary orbit around the sun (heck, put it on a comet), and
>then jumping off with your "sail in the wind", so to speak.  This get
>you a fair amount of "free" velocity, plus you make the most of the
>inverse-squared nature of light.  Maybe even getting a boost from the
>solar wind.

A talk on solar sails at Planetfest last week revealed that one plan for
getting some really spectacular velocity out of a solar sail is to hide
it behind an opaque disk, and fly it in really close to the sun, then
jettison the disk with a florish and ride the photons while they're fresh.
I forget what kind of velocity that produces but it does get the highest
velocity you can attain with a s.s..  Certainly at the Earth's orbit the
contribution of the solar wind to s.s. thrust is less than 1%, so don't
expect much help from that.  This talk was given by a member of the World
Space Foundation, one of those organizations like Space Studies Institute
that spends less time talking and more time building neat stuff, like a
solar sail, in their case.

Peter Scott ([e-mail])

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

Date: 31 Aug 89 02:34:39 GMT
From: aramis.rutgers.edu!athos.rutgers.edu![e-mail]  (Steve Masticola)
Subject: Re: NASA Headline News for 08/30/89 (Forwarded)

Peter E. Yee writes:

> Voyager 2 is continuing its journey outward and is now almost
> five million miles from Neptune.  Next spring, mission managers
> will turn the spacecraft's cameras, infrared detector and light
> sensors off to preserve power.

Can the RTG be conserved by reducing power use, or are the instruments
being shut off because there won't be adequate power available for
them at that time? The former seems unlikely, unless the fission rate
in the RTG can be controlled.

> Scientists should be able to track Voyager for another 25 years
> until its power supply expires.

When is Voyager expected to meet the heliopause? Was any maneuvering
done at Neptune to shorten this time?

- Steve ([e-mail])

P.S. Please, please, don't let what happened to ALSEP happen to Voyager!

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

Date: 31 Aug 89 06:18:13 GMT
From: unmvax!ogccse!blake![e-mail]  (William Lewis)
Subject: Solar sails (was Re: Pluto fly-by)

Presumably in an article, [e-mail] (Peter Scott) writes:
>A talk on solar sails at Planetfest last week revealed that one plan for
>getting some really spectacular velocity out of a solar sail is to hide
>it behind an opaque disk, and fly it in really close to the sun, then
>jettison the disk with a florish and ride the photons while they're fresh.
>I forget what kind of velocity that produces but it does get the highest
>velocity you can attain with a s.s..     [ .... ]

   Now, I don't claim to be an expert on solar sails at all, but
this doesn't sound quite right.... An opaque disk would only cut
the thrust by half, ignoring the solar wind, or by less than half
if the solar wind is non negligible. It would be much, much better
(IMUO) to drop in keeping the sail edge-on to the sun (if you use
a flat one), or not unfolding the sail until you get there. Say,
if you use a spinning sail, the second is easier, but if you use
a rigid sail, probably the first is doable. (Myself, I don't trust
wires to keep my sail in place, or active systems to keep it aligned
... I prefer conical spinning sails ... but I'll leave that to the
people who know about masses and strengths and whatnot in more detail..
i.e, not me.)

   [halfserious mode on...] what this network needs is a sci.space.sf-lovers
group. That way I can be enthusiastic about things without worrying about
reality and all that nasty stuff. [mode off]


      --- phelliax  ---   [e-mail]  ---
      gee, that looks almost like a signature.

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

Date: Thu, 31 Aug 89 08:52:47 MEZ
From: [e-mail]
Comment: CROSSNET mail via MAILER@CMUCCVMA

Date: 31 August 1989, 08:25:20 MEZ
From: OE2N     at DLRVM   bitnet
      Peter Seige
To:   SPACE    at ANDREW.CMU.EDU
Subject:  Voyager Neptun/Triton  Encounter



        The last few days I heard and read a lot about Voyager encounter
        with NEPTUN and TRITON. So far I could not get any good information
        about the maximum resolution of the images during these encounters.

        Is there anybody (probably from JPL) who can get me more
        informations about that.


                                              Peter Seige

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

Date: 31 Aug 89 06:00:17 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Pluto fly-by

Unveiling a solar sail near the Sun would be fun, but as previously discussed
here it's very expensive powering something there to begin with.
--
"We walked on the moon --    ((    Tom Neff
    you be polite"         ))     [e-mail]

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

Date: 31 Aug 89 05:58:51 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Post- Star Wars space habitability

I think near-earth space is about as uninhabitable as it's going to get. :-)

Killing ICBMs with SDI won't itself pollute space with debris, because the
things being zapped are ballistic and suborbital.  The debris will re-enter.
If it ever happens, worry about the ecosphere not space, because SDI won't
get 'em all.

ASAT warfare could make space crunchy underfoot.  SDI is just a tempting
set of targets.
--
"We walked on the moon --    ((    Tom Neff
    you be polite"         ))     [e-mail]

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

End of SPACE Digest V10 #27
*******************