Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO304.TXT

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Date: Sat, 10 Oct 92 05:03:03
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #304
To: Space Digest Readers
Precedence: bulk


Space Digest                Sat, 10 Oct 92       Volume 15 : Issue 304

Today's Topics:
                           (none) (2 msgs)
                 ASTRONOMY CAMPS FOR TEENS AND ADULTS
                   Drop nuc waste into sun (3 msgs)
             ENV SATELLITE SHUTDOWN IN DEC 1992 (3 msgs)
                      Galileo Update - 10/09/92
     Mass driver literature (was Re: Transportation on the Moon.)
                 Pioneer Venus Briefing Set for Today
                       SETI positive? (3 msgs)
                     Transportation on the Moon.

    Welcome to the Space Digest!!  Please send your messages to
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----------------------------------------------------------------------

Date: 9 Oct 92 17:39:41 GMT
From: Herman Rubin <[e-mail]>
Subject: (none)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>
>Subject: Re: Clinton and Space Funding
>
>In article <[e-mail]> [e-mail] (Herman Rubin) writes:
>>
>>There is another, and extremely important, reason for colonization, namely,
>>escape from an oppressive government.  The Spanish colonies were moderately
>>successful only where they were eminently profitable; the missions in
>>California must be considered a failure.  The French colonies in Canada
>>and Louisiana were not particularly successful.  On the other hand, the
>>English colonies to escape oppression were generally quite successful,
>>even bringing in others.  A major part of the US immigration in the 19th
>>century was to escape oppression.


>I have one simple question.
>If you're trying to "...escape from an oppressive government.", how are you
>going to escape from this "oppressive government" when they're funding this
>project?

>Keep searching until a group of private corporations get together and fund a
>majority of this project.

You seem to have missed my other postings on this topic.  I, and many others,
have been advocating that the government allow private space expenditures AS
THOSE WISHING TO SPEND THE MONEY WANT TO.  At this time, it is illegal for
an American to launch anything anywhere in the world without US government
approval.

Get the government out of restricting people, and the money can be raised by
those who feel it worthwhile.  We have some organizations now, and more can
be formed, to get the job done.  Exploration has been done by non-profit
organizations as well as for profit, and quite a bit of it, and the various
organizations can cooperate, much more easily than they can work through a
government monopoly.

The Planetary Society might fund unmanned exploration, there may be groups
pushing for orbital work, for asteroid missions, etc.  These groups are
likely to share knowledge and expertise, but it would still be the case
that each group would concentrate on funding what it felt to be
important, without the need to get a consensus on priorities.

For-profit companies would also invest in what they think will bring the
returns.  Of course speculation must occur; WE DO NOT KNOW, and we will
not find out sitting on earth.
--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: [phone]
[e-mail] (Internet, bitnet)
{purdue,pur-ee}!pop.stat!hrubin(UUCP)

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

Date: 9 Oct 92 20:17:06 GMT
From: "Michael V. Kent" <[e-mail]>
Subject: (none)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Herman Rubin) writes:
>
>You seem to have missed my other postings on this topic.  I, and many others,
>have been advocating that the government allow private space expenditures AS
>THOSE WISHING TO SPEND THE MONEY WANT TO.  At this time, it is illegal for
>an American to launch anything anywhere in the world without US government
>approval.

This isn't that unusual if you think about.  I can't drive a car without the
government's permission (driver's liscence), my car can't be driven off my
property w/o govt's permission (lisence plates).  I can't get married, go
fishing or hunting (or flying!!) either.  I can't do much of anything that
might endanger society or some subgroup thereof.

The difficulty of obtaining the proper lisence is proportional to the damage
that could be done if something went wrong.  Marriage and fishing lisences
are easy to get, driver's lisences a bit harder, and pilot's lisences harder
still.  It shouldn't surprise anyone a lisence to launch several tons of
high explosives over people's heads is even harder.

Those who prove they can launch rockets safely can get a lisence.  Both
General Dynamics and McDonnell Douglas have one, and they can launch payloads
without much further trouble.  Sounds reasonable to me.  It certainly has
ample precedent.

Mike

--
Michael Kent                                   [e-mail]
McDonnell Douglas                              Rensselaer Polytechnic Institute
All facts in this post are based on publicly available information.  All
opinions expressed are solely those of the author.    Apple II Forever !!

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

Date: 9 Oct 92 18:55:56 GMT
From: Jeff Regester <[e-mail]>
Subject: ASTRONOMY CAMPS FOR TEENS AND ADULTS
Newsgroups: sci.space,sci.astro,alt.sci.planetary

The Steward Observatory Astronomy Camps for Adults and Teens for the
coming winter, spring and summer have been scheduled. The dates are:
   Advanced Adult Camp   Feb 18-21
   Beginning Adult Camp  Apr 23-25
   Beginning Teen Camp   Jun 7-14
   Advanced Teen Camp    Jun 18-25

The Astronomy Camps are run by Steward Observatory (Univ. of Arizona)
as a non-profit educational outreach project. Attendees use the 40",
60", and 61" research telescopes of the Mt Lemmon and Mt Bigelow
Observatories (north of Tucson) operated by NASA and Steward. A 16"
Schmidt camera and numerous portable telescopes are also available.

The Adult Camps are during weekends and consist of observing (using
eyepieces, astrophotography with film and CCDs, and photometry,
according to participant interest) and lectures, demonstrations, and
discussions. Tours of research and engineering facilities, such as the
spin-casting facilities of the Steward Observatory Mirror Lab, are
also conducted.

The Teen Camps (for ages 13 to 17) each last a week, four nights of which
are spent observing. Activities include those of the Adult Camps plus tours
of Kitt Peak facilities, science demonstrations, lectures (space program,
archaeoastronomy, space art with Kim Poor, etc.) and other activities
(model rockets, volleyball, orienteering in the mountains, etc.)

For both Teens and Adults, the Advanced camps are for those who have
previously attended a Beginning Camp or who have prior amateur astronomy
experience. The Camps are run by Dr Donald McCarthy of Steward Observatory.
Other Steward faculty and graduate students, as well as personnel of Flandrau
Planetarium, participate as guest speakers and camp counselors.

To receive more info about the Camps, contact either

 Don McCarthy  voice: [phone]
               email: [e-mail]
               usps:  Steward Observatory, U of A, Tucson AZ, 85721

    or

 Jeff Regester voice: [phone]
               email: [e-mail]
               usps:  Steward Observatory, U of A, Tucson AZ, 85721


     Jeff Regester
     counselor, U of A Astronomy Camps

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

Date: 9 Oct 92 21:22:46 GMT
From: Pat <[e-mail]>
Subject: Drop nuc waste into sun
Newsgroups: sci.space

Hey if this is stupid, please enlighten me.

what if you sent a package on a venus gravity assist, but retrograde, so that
the momentum transfer goes  counter orbital direction,  would that be cheaper then   solar escape?    a little gravity well, and bang you might have
saved some money.

let me know

pat

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

Date: 9 Oct 92 21:17:19 GMT
From: Don Roberts <[e-mail]>
Subject: Drop nuc waste into sun
Newsgroups: sci.space

[e-mail] writes:

[lots of interesting obital mechanics deleted]

>If the nucleopaths on Earth won't agree to the best solution, which
>is the hole in the ground on Earth, then the next best solution
>might be a lunar hole in the ground.

As long as we're asking and answering what are probably frequently asked
questions, I'll ask one:

Are there serious technical objections to dumping suitably "leak-proof"
containers (i.e., whatever they plan to use in a Yucca Mt.-type repository)
into a subduction zone at the bottom of the ocean? Assuming no leaks, we
have a much cheaper version of the "dump it on Venus" or "dump it into the
Sun" approach. Assuming small leaks *do* develop, the stuff would be pretty
well diluted, yes?

Personally, I prefer salt mines, or some other approach that allows us to
keep an eye on the stuff, and have access to it if it ever proves useful.
But it's a thought. Comments?

I guess I should know the answer, but I'm a plasma physicist by training,
and we can't produce enough radioactivity to make a good watch-dial...yet.
--
 Dr. Donald W. Roberts
   University of California                                     Physicist
   Lawrence Livermore National Laboratory        Recreational Bodybuilder
   [e-mail]                                          Renaissance Dude

 The ideas and opinions expressed here do not represent official policies
 of Lawrence Livermore National Laboratory,  the University of California,
                or the United States Department of Energy.

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

Date: Fri, 9 Oct 1992 22:37:37 GMT
From: Paul Dietz <[e-mail]>
Subject: Drop nuc waste into sun
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Don Roberts) writes:

> Are there serious technical objections to dumping suitably "leak-proof"
> bcontainers (i.e., whatever they plan to use in a Yucca Mt.-type repository)
> into a subduction zone at the bottom of the ocean?

It's a non-starter.  First of all, subduction is very slow.  Plates
only move maybe 5 cm per year.  So, in 10,000 years, the stuff has
moved only 500 meters.  It's not quickly sucked down into the mantle.

Second, the sediments at a subduction zone are very active.  They
get scraped off and form "mud volcanoes" on the ocean floor.  Not
where you want to put waste.

It would make more sense to put them far away from subduction zones,
in the ocean floor, so that by the time they are subducted they
are decayed away.  But this is just sea-bed disposal, which has
been considered for years.

    Paul F. Dietz
    [e-mail]

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

Date: 9 Oct 92 19:47:52 GMT
From: "Michael V. Kent" <[e-mail]>
Subject: ENV SATELLITE SHUTDOWN IN DEC 1992
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Michael W. Rowland) writes:
>This is a repost of 6 Oct. posting (revised)...
>
>     NUMBUS-7
>
>     Total Ozone Measurement System (TOMS)

Is this real?  NASA plans to shut down TOMS?  Why?

This is about the last instrument on the last satellite I expected to be
voluntarily shut down.

>Budget cuts are specified in House Conference Report 102-902
>that is attached to HR 5679, Sept. 24, 1992.

I guess this is a likely explanation.  Were these satellites mentioned by name
or was it just a line item that got hacked to death?

Mike

--
Michael Kent                                   [e-mail]
McDonnell Douglas                              Rensselaer Polytechnic Institute
All facts in this post are based on publicly available information.  All
opinions expressed are solely those of the author.    Apple II Forever !!

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

Date: 9 Oct 92 20:14:56 GMT
From: Henry Spencer <[e-mail]>
Subject: ENV SATELLITE SHUTDOWN IN DEC 1992
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Michael V. Kent) writes:
>>     NUMBUS-7
>>
>>     Total Ozone Measurement System (TOMS)
>
>Is this real?  NASA plans to shut down TOMS?  Why?
>This is about the last instrument on the last satellite I expected to be
>voluntarily shut down.

Bear in mind that there is a new TOMS now in orbit aboard a Soviet weather
satellite.  The one aboard Nimbus 7 is pretty old, although I believe it
is still more or less working.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: Fri, 9 Oct 1992 20:44:55 GMT
From: [e-mail]
Subject: ENV SATELLITE SHUTDOWN IN DEC 1992
Newsgroups: sci.space

In article <[e-mail]>
[e-mail] (Michael W. Rowland) writes:

>
>This is a repost of 6 Oct. posting (revised)...
>
>We at Langley Research Center received news on Thursday, October 2,
>1992 that NASA intends to shutdown the following satellites in
>December to save about $15M:
>
>     NUMBUS-7
>
>     ERBS
>
>     NOAA-9 (partial?)
>
>     NOAA-10 (partial?)
>
>     UARS (SPRING 1993)
>
>Some of the following experiments that will terminate when
>their satellites are shutdown are:
>
>     Stratospheric Aerosol Measurement II  (SAM II)
>
>     Earth Radiation Budget Experiment (ERBS) (3)
>
>     Stratospheric Aerosol and Gas Experiment II (SAGE II)
>
>     Total Ozone Measurement System (TOMS)
>
>     Halogen Occultation Experiment (HALOE)
>
>     Microwave Limb Sounder (MLS)
>
>No plans have been stated to restart the satellites.
>
>Budget cuts are specified in House Conference Report 102-902
>that is attached to HR 5679, Sept. 24, 1992.
>
>Mike Rowland
>
>Mike Rowland, Aerosol Research Branch, MS 475
>NASA Langley Research Center, Hampton VA 23681
>internet: [e-mail]

The UNOFFICIAL word I get is that NASA is dropping its direct downlink from
the satellites listed in the previous post.  The satellites previously
listed were NOAA satellites and will continue to be managed by NOAA.

It is however true that at least one NOAA satellite will be let go due to
ground limitations when a new NOAA satellite is launched.

                                    - Karl J. Pitt

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

Date: Sat, 10 Oct 1992 04:32:50 GMT
From: Ron Baalke <[e-mail]>
Subject: Galileo Update - 10/09/92
Newsgroups: sci.space,sci.astro,alt.sci.planetary

Forwarded from Neal Ausman, Galileo Mission Director

                                   GALILEO
                         MISSION DIRECTOR STATUS REPORT
                                 POST-LAUNCH
                            October 2 - 8, 1992

SPACECRAFT

1.  During the period of October 3 through October 4, a navigation cycle was
performed.  This navigation cycle provided near-continuous acquisition of
two-way doppler and ranging data during four consecutive passes of the
spacecraft over DSS-63 (Madrid 70 meter antenna).  This data will improve
orbit determination in support of the TCM-15 (Trajectory Correction Maneuver
#15) scheduled for October 9.

2.  On October 5, a NO-OP command was sent to reset the command loss timer
to 264 hours, its planned value for this mission phase.

3.  On October 5, a routine sun vector update was performed.  This sun vector
is valid through October 27.

4.  On October 5, an Ultra-Stable Oscillator (USO) test was performed to
verify the health status of the USO and collect gravitational red shift
experiment data; long term trend analysis is continuing.

5.  On October 6, real-time commands were sent to temporarily configure the
spacecraft telemetry rate to 1200 bps, which has not been sustainable since
June 1991.  On October 7, the spacecraft was configured to 40 bps uncoded
telemetry and then back to 1200 bps on October 8.

6.  On October 6, a periodic RPM (Retro-Propulsion Module) 10-Newton thruster
maintenance activity was performed; 10 of the 12 thrusters were "flushed"
during the activity.  The P-thrusters were not flushed because they were used
to perform science turn (SITURN) activities on the same day.  Spacecraft
performance throughout the activity was normal.

7.  On October 7, the spacecraft performed a 14.5 degree SITURN.  The purpose
of the SITURN was to maintain the spacecraft within plus or minus 13 degrees
of the sun while at the current solar distance.

8.  On October 7, the Earth vector and Earth stars were updated to the
spacecraft's present attitude.  This change implements the attitude
maintenance strategy required in the case of an AACS (Attitude and
Articulation Control Subsystem) POR (Power On Reset).  If a fault occurs
which terminates the currently executing sequence, the spacecraft will
maintain its current attitude.

9.  On October 7, cruise science Memory Readouts (MROs) were performed for
the Extreme Ultraviolet Spectrometer (EUV), Dust Detector (DDS), and
Magnetometer (MAG) instruments.  Preliminary analysis indicates the data
was received properly.

10. On October 8, spacecraft telemetry maps were updated for the 1200 bps
capability.

11. On October 8, the Trajectory Correction Maneuver (TCM-15) memory load was
uplinked to the spacecraft.  During the initial attempt, one of the eight
TCM-15 messages was rejected by the spacecraft.  The entire High Level Module
(HLM) sequencing memory was readout, verified and the rejected message
retransmitted and verified via memory readout.  This commanding incident is
under investigation.

12. The AC/DC bus imbalance measurements exhibited some change.  The AC
measurement has ranged from 12DN to 16DN and now reads 16 DN (3.7 volts).
The DC measurement has ranged from 116 DN (13.5 volts) to 135 DN (15.8 volts)
and now reads 126 DN (14.7 volts).  These measurement variations are
consistent with the model developed by the AC/DC special anomaly team.

13. The Spacecraft status as of October 8, 1992, is as follows:

       a)  System Power Margin -  69 watts
       b)  Spin Configuration - Dual-Spin
       c)  Spin Rate/Sensor - 3.15rpm/Star Scanner
       d)  Spacecraft Attitude is approximately 11 degrees
           off-sun (leading) and 16 degrees off-earth (lagging)
       e)  Downlink telemetry rate/antenna-1200 bps (coded)/LGA-1
       f)  General Thermal Control - all temperatures within
           acceptable range
       g)  RPM Tank Pressures - all within acceptable range
       h)  Orbiter Science- UVS, EUV, DDS, MAG, EPD, and HIC are
           powered on
       i)  Probe/RRH - powered off, temperatures within
           acceptable range
       j)  CMD Loss Timer Setting - 264 hours
           Time To Initiation - 263 hours


UPLINK GENERATION/COMMAND REVIEW AND APPROVAL:

1.  The Trajectory Correction Maneuver (TCM-15) design package was approved
by the Project on October 2, 1992.  Additionally, the TCM-15 maneuver was
approved for transmission by the Project on October 7, 1992.  TCM-15 is a one
portion maneuver scheduled to execute on October 9 consisting of one axial
segment and one lateral segment.  The estimated total delta velocity for
TCM-15 is .716 m/s.

2.  The EE-12 (Earth-Earth 12) Final Cruise Plan was approved by the Project
on October 5, 1992.  This sequence covers spacecraft activities from
January 20, 1993 to April 12, 1993.

3.  The Dual Drive Actuator (DDA) pulse mini-sequence No. 4 memory load was
approved for transmission by the Project on October 8.  This mini-sequence
covers spacecraft activities associated with the DDA 10-pulse hammer test
from October 12 to October 15.


TRAJECTORY

     As of noon Thursday, October 8, 1992, the Galileo Spacecraft trajectory
status was as follows:

    Distance from Earth         37,027,900 miles (.40 AU)
    Distance from Sun           125,287,800 miles (1.35 AU)
    Heliocentric Speed           61,600 miles per hour
    Distance from Jupiter        618,941,500 miles
    Round Trip Light Time        6 minutes, 44 seconds


SPECIAL TOPIC

1.  As of October 8, 1992, a total of 8237 real-time commands have been
transmitted to Galileo since Launch.  Of these, 3288  were pre-planned in the
sequence design and 4949 were not. In the past week, 6 real time commands were
transmitted and pre-planned in the sequence design.  In addition, 5677
mini-sequence commands have been transmitted since March 1991; 3519 were
pre-planned and 2158 were not.  In the past week, no mini-sequence commands
were transmitted.  Major command activities this week included commands to
reset the command loss timer, configure the spacecraft telemetry rate to
1200 bps, and uplink the TCM-15 memory load.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Einstein's brain is stored
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | in a mason jar in a lab
|_____|/  |_|/       |_____|/                     | in Wichita, Kansas.

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

Date: 9 Oct 92 21:42:38 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: Mass driver literature (was Re: Transportation on the Moon.)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Rajesh Batra) writes:
> We have been given a Senior Design Project based on a fictious
> premise that ice has been found at the North Pole of the Moon.  Our moon base
> (it's the year 2016, by the way) is located at the equator. Our Mission is
> to bring back this ice from the North Pole to our production facility plants
> (located at the equator as well) for extraction of Hydrogen and Oxygen.
> [...] We have come up with several ideas including Pipelines,
> Rockets, and Rail Guns. We are delivering about 2 tons of rock (containing ice)
> a day.
>
> If anyone can direct me to abstracts that have been written concerning
> Rail Guns please do not hesitate to email me.

[I e-mailed Rajesh, but it seems this might be of interest to others, too.]

Interesting design problem.  Offhand, it seems wrong to drag the ice
to the equator and do the processing there, but if that's your
assignment...

(Also, if you have the infrastructure to build a railgun launcher and
associated power supply, logistics, operations and maintenance stuff
at the poles, you can probably afford to build your chemical
engineering plant there instead!  Then you can ship anything you want
anywhere on the Moon or beyond, using the same H2-O2 rockets you use
to supply your base, refueling them at the Pole. Solar cells or
mirrors on a tall tower can give you power 28 days around the clock
there, too.)

Hope Cincinatti has some good engineering libraries;  if not, talk to
your librarian about the Magic of Interlibrary Loan.  And get a roll
or two of dimes for the photocopier.

Start with Arthur C. Clarke, "Electromagnetic Launching as a Major
Contribution to Spaceflight," *Journal of the British Interplanetary
Society*, v. 9 n. 6, November 1950, p. 261-267.  Unless you want to
start with an extremely obscure 1937 science fiction novel called
*Zero to Eighty* by Akkad Pseudoman, a pseudonym (Oh, no kidding.) for
E.F. Northrup.

Generally speaking, the best places to look for information are the
"Princeton Conferences,"  with titles like *Proceedings of the Nth
Conference on Space Manufacturing*, published by the AIAA.

I have the title of only one of them explicitly: *Space Manufacturing
5: Engineering with Lunar and Asteroidal Materials*, edited by Barbara
Faughnan and Gregg Maryniak, AIAA (1985).

Also, every couple of years, there is a big conference on
electromagnetic launcher technology, and it appears in *IEEE
Transactions on Magnetics* as an extra-thick issue.  For instance,
IEEE T on M, V.27, No. 1, January 1991.

I have some specific early references (I met Henry Kolm in 1979 and he
sent me a bunch of papers).

Kolm, H., "An electromagnetic `slingshot' for space propulsion,"
*Technology Review*, Jun 1977, p. 61-66.
Good semi-technical overview.

Kolm, H., Mongeau, P., "An alternative launching medium," *IEEE
Spectrum*, April 1982, p. 30-36.

A bunch of papers in the first two Princeton Conference on Space
Manufacturing (1977 and 1979) by Kolm, Kevin Fine, Peter Mongeau, and
Fred Williams.

Looking at my records, the Princeton conferences have so much stuff on
this it's not worth typing the titles individually.

     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |     Bill Higgins   Fermi National Accelerator Laboratory
 \       /     Bitnet:     [e-mail]
   -   -       Internet:  [e-mail]
     ~         SPAN/Hepnet:      43011::HIGGINS

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

Date: 9 Oct 92 21:51:04 GMT
From: Duane F Marble <[e-mail]>
Subject: Pioneer Venus Briefing Set for Today
Newsgroups: sci.space,sci.astro,alt.sci.planetary

Since it vanished "out of sight" I am waiting for the articles in
National Enquirer, etc., about aliens snatching the vehicle.
--
Duane F. Marble                   E-mail: [e-mail]
Department of Geography                Telephone: [phone]
The Ohio State University
Columbus, Ohio 43210                   Fax: [phone]

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

Date: 9 Oct 92 19:56:20 GMT
From: Jeff Bytof <[e-mail]>
Subject: SETI positive?
Newsgroups: sci.space,sci.astro

>   Curiosity: why yellow?  Don't main sequence orange and red stars last longer
>than yellow ones?  Is there some reson to think cooler stars than the sun won't
>develop technological civilizations?

The NASA targeted search will be looking at stars of spectral class F, G
and K.  M class red dwarfs (you don't want to mess with red giants!) would
have much smaller ecospheres than the sun because they are less luminous,
and therefore the probability of finding a habitable planet in the ecosphere
of such a star would be very small.  If a planet was in a red
dwarf ecosphere, it might be close enough to the star to have its rotation
tidally locked (which might have interesting implications for weather),
though I'm not sure about that.

>   For that matter, wouldn't _any_ star system be a candidate for an
>automated communications relay left by a self reproducing probe?  A
>paranoid might think another civilization would attempt to contact us
>only through an offset communications device :).

The NASA sky survey is designed to be complementary to the targeted
search, though not quite as sensitive to weak signals.  Automated
probes may also be floating between the stars, perhaps in retrograde
galactic orbits, passing by many more stars per unit time than if they
following the general galactic rotation.

--------------------
[e-mail]

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

Date: 9 Oct 92 21:36:24 GMT
From: Dave Nash <[e-mail]>
Subject: SETI positive?
Newsgroups: sci.space,sci.astro

In article <[e-mail]> [e-mail] (Daniel A Ashlock) writes:

>   Curiosity: why yellow?  Don't main sequence orange and red stars last longer
>than yellow ones?  Is there some reson to think cooler stars than the sun won't
>develop technological civilizations?


The red and orange guys _do_ last longer -- a lot longer, in most cases --
but as I (perhaps wrongly) understand it, really small stars (e.g., Proxima
Centauri or Barnard's Star) are so feeble that a planet close enough to the
star to receive enough energy from it to be Earthlike (warm enough for liquid
water, e.g.) would become slowed by tides until its rotation period equals its
year.  Much like the case with our Moon, which is "locked" in this manner to
the Earth.  This means one hemisphere of the planet will permanently
face the star and... well, you could guess the rest.  An interesting
book called _Habitable Planets for Man_  (I forget the author) makes a
back-o'-the-envelope calculation of the sorts of conditions required for this,
and concludes that  the smallest star that can avoid the problems with
tidal locking is a K2 main sequence star -- about like Epsilon Eridani, but
much more luminous than red dwarfs, which are M class.

This was, of course, a rough estimate, but if the tidal-locking idea is correct
then it appears essentially all M (red) and most K (orange) dwarfs would not be
the most suitable candidates for _originating_ extraterrestrial life.

Any one out there with more knowledge of this possible problem?  I only have
the argument from this one book and I'm not sure if there are any more recent
arguments for or against the tidal-locking idea.

>   For that matter, wouldn't _any_ star system be a candidate for an
>automated communications relay left by a self reproducing probe?  A

Yeah, at least till it goes supernova or red giant (grin)...

>Dan
>[e-mail]


--
David Nash                  | Gradual Student, Chemistry
                            | University of Illinois (Urbana)
([e-mail])    | This .sig is made of 100% recycled electrons.
([e-mail])   | No binary trees were killed to make it.

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

Date: 9 Oct 92 21:58:57 GMT
From: Jeff Bytof <[e-mail]>
Subject: SETI positive?
Newsgroups: sci.space,sci.astro

>An interesting book called _Habitable Planets for Man_  (I forget the
>author)

Stephen Dole (and with Isaac Asimov wrote a less technical treatment
"Planets for Man")

Dole retired from the Rand Corporation in 1982.

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Date: 9 Oct 92 21:04:42 GMT
From: Jeff Bytof <[e-mail]>
Subject: Transportation on the Moon.
Newsgroups: sci.space

>        We are looking for any feasible transportation ideas that could
>accomplish this task. We have come up with several ideas including Pipelines,
>Rockets, and Rail Guns. We are delivering about 2 tons of rock (containing
>ice) a day.

My God, as far as we know the Moon's as dry as a bone, and we're talking
about mining ice on it!  Even if there IS ice, how do we know there's
going to be enough to support whatever operation is proposed?
My guess is that whatever ice there was at the Lunar poles has
been blasted to Kingdom Come.

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End of Space Digest Volume 15 : Issue 304
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