Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_7/V13_772.TXT

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Subject: SPACE Digest V13 #772

SPACE Digest                                     Volume 13 : Issue 772

Today's Topics:
              Re: Fred's Operatic Death
             Re: Mining El Dorado
             Re: Mining El Dorado
              Re: Fred's Operatic Death
               Magellan Images
             Re: == No Subject ==
          Trying to contact oldtime SCI.SPACE people
       Earth-crossing water (was Re: Platinum-group..)

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription requests,
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             [e-mail]

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Date: 19 Jun 91 19:33:59 GMT
From: agate!spool.mu.edu!mips!swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Organization: U of Toronto Zoology
Subject: Re: Fred's Operatic Death
References: <[e-mail]>, <SHAFER.91Jun181157, <SH
Sender: [e-mail]
To: [e-mail]

In article <[e-mail]> [e-mail] (Mary Shafer) writes:
>Nick has informed me that "Public employees slandering [him] on the
>net are cruising for a bruising."

Ah yes.  If you can't refute them, intimidate them.
--
"We're thinking about upgrading from    | Henry Spencer @ U of Toronto Zoology
SunOS 4.1.1 to SunOS 3.5."              |  [e-mail]  utzoo!henry

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

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Date: 20 Jun 91 01:50:07 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!ptimtc!nntp-server.caltech.edu![e-mail]  (Steinn Sigurdsson)
Organization: Theoretical Astrophysics, Caltech
Subject: Re: Mining El Dorado
References: <[e-mail]>, <[e-mail]>, <[e-mail]>
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In article <[e-mail]>, jdnicoll@watyew (James Davis Nicoll) writes:
>>>

    Why assume that you must use rockets or bombs to move
asteroids, after all you have plenty of time (for mining - different
problem for dinasaur killers but then the deltaV is smaller) - instead
use continuously operated ion thrusters and/or solar sails. With the
thrusters you can take a long time of low continuous acceleration,
your reaction mass will mostly come from the asteroid, and your
acceleration only depends on the power available - start with solar
cells or small nuclear reactor and either build more cells in situ or
ship more power units - you can in principle also build more thrusters
in situ. - of course unless you have a continuous stream of these
things the interest on your capital costs will wipe you out before the
first one arrives, so you use the old railroad trick, capitalise a
dummy company, file bankruptcy _after_ you get the think moving and
have someone else pick it up in earth orbit...

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

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Date: 19 Jun 91 14:47:14 GMT
From: agate!spool.mu.edu!caen!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!watserv1!watdragon!watyew![e-mail]  (James Davis Nicoll)
Organization: University of Waterloo
Subject: Re: Mining El Dorado
References: <[e-mail]>, <[e-mail]>, <[e-mail]>
Sender: [e-mail]
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>>
>>* The energy required to achieve that delta-v would likely disrupt or
>>  vaporize the asteroid.  For example, to achieve 4,000 m/s the power
>>  output is (1e10 kg)(4,000 m/s)^2/(.01 s) = 1.6e19 watts assuming a
>>  propogation time of .01 second.  Of course, we could do multiple
>>  explosions, but hundreds to thousands of small nuclear warheads starts
>>  to get expensive.

    I'm still trying to get a handle on the cost of using nukes to move
El Dorado. ED masses 10**10 kg, and we want to cause a delta-v of 4000 m/s.
If the Isp of our system is the same as the pulsed-fission idea Orion would
have used (50000 s), then the mass ratio would be 1.008. We'll need to throw
8.1x10**7 kg at 500,000 m/s. The Ek works out to 1.0x10**19 J, or about the
2400 megatonnes. That's, what, about one quarter the world's supply of
nuclear explosives? Two questions:

    1: How much would it cost to built 2400 1 MT nuclear propulsion units?

    2: How much would they weigh? I have dim memories of an article in
        Scientific American on cruise missiles, and I *think* the
        100 KT warhead was about 250 kg. *If* that's correct, then
        we'd be looking at about 6000 tonnes of nuclear explosives.
        6000 tonnes is a lot of shuttle launches.

    Geez, that value for Ek looks low.

                                James Nicoll

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

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Date: 20 Jun 91 01:53:59 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!ptimtc!nntp-server.caltech.edu![e-mail]  (Steinn Sigurdsson)
Organization: Theoretical Astrophysics, Caltech
Subject: Re: Fred's Operatic Death
References: <[e-mail]>, <SHAFER.91Jun181157, <SH
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In article <[e-mail]>, shafer@skipper (Mary Shafer) writes:
>I wrote:
>
>>In article <[e-mail]> [e-mail] (James Davis Nicoll) writes:
>>>>  'Do NASA employees post self-serving propaganda (also 'should NASA...')'
>>>>  argument deleted.
>>
>>>I have the damned feeling I've seen this thread before. How did the
>>>tiff that ended with Ms Shafer briefly leaving sci.space start?
>>
>>Wit Nick Szabo claiming that NASA employees should only post stuff that
>>Nick thought was OK.  That is, it was OK for the informational stuff
>>to appear, but if one disagreed with Nick .....
>
>Nick has informed me that "Public employees slandering [him] on the
>net are cruising for a bruising."
>
>It was not my intent to slander Nick and if his feelings, amour propre,
>or net reputation were damaged by my comment, I apologize and retract
>my comment.

    I'm not a public employee - Nick, your posts are getting way
out of line. It has become my distinct impression that in fact you
_do_ wish to suppress the honest expression of people's opinion
based on the fact they work for government organisations. I disagree
with some of what you say, agree with some of it, but I think you
are going too far - please try to lighten up! It will make everybody's
life a little less stressed.

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

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Date: 20 Jun 91 05:38:00 GMT
From: agate!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!jato!kelvin.jpl.nasa.gov![e-mail]  (Ron Baalke)
Organization: Jet Propulsion Laboratory
Subject: Magellan Images
Sender: [e-mail]
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                            ===================
                              MAGELLAN IMAGES
                              June 19, 1991
                            ===================

     I've placed 17 more Magellan images at the Ames SPACE archives, bringing
the Magellan total to 36 images.  These new images are in VICAR format which is
the format used at the Image Processing Lab (MIPL) at JPL.  The images are
obtainable via anonymous ftp from ames.arc.nasa.gov (128.102.18.3), and are in
the pub/SPACE/VICAR directory.  All of the Magellan images I've put at the
Ames site are public release images from the Magellan project, and are in the
public domain and can be freely distributed.  These new images are *not* on the
first Magellan CDROM released earlier this year.

     The new Magellan files and their sizes are:

          alcott.img       1,049,600 bytes
          ammavaru.img     1,312,000 bytes
          arachcom.img       971,880 bytes
          barton.img       2,626,020 bytes
          flows.img        3,616,434 bytes
          golubnew.img     1,025,145 bytes
          golubold.img     1,025,145 bytes
          gulamons.img       914,328 bytes
          hestia.img       1,422,603 bytes
          lakshmif.img       822,584 bytes
          mead.img         1,312,000 bytes
          navka.img        2,521,800 bytes
          ovda.img         1,180,310 bytes
          pandora.img        918,528 bytes
          sifflows.img       621,600 bytes
          test25pvo.img    1,006,304 bytes
          test25rm.img     1,006,304 bytes

     All of the VICAR images have a corresponding caption files (with a .txt
extension) which contains detailed descriptions of the image.  Make sure
you are in binary mode when transferring the image files, and in ASCII mode
when transferring the txt files.

     The VICAR images can be viewed on an IBM PC computer with the IMDISP
program stored in a zip file called imdisp56.zip, located in the
pub/SPACE/SOFTWARE directory, at the same Ames site.  IMDISP is the same
program distributed with the Voyager and Magellan CDROMs.  Since I am one of
the programmers for IMDISP, I would welcome any feedback on IMDISP, including
any problems encountered with its use or suggestions on improving the program.
A new version of IMDISP will be released in a about a couple of weeks; I'll
post an an announcement when it is ready.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
     | | | |  __ \ /| | | |     Jet Propulsion Lab |
  ___| | | | |__) |/  | | |__   M/S 301-355        | "Imagination is more
 /___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | important than knowledge"
 |_____|/  |_|/       |_____|/                     | Albert Einstein

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

Date: 16 Jun 91 18:39:45 GMT
From: nuchat!lobster!n5abi![e-mail]
Subject: Re: == No Subject ==


> #In article <[e-mail]> [e-mail] (Gary Coffman) writes:
> #
> ##The only manmade structure that can be seen with the naked eye from
> space,
> ##the Great Wall of China, has been around for a fair amount of time
> in
> #.......
> #
> >BZZZT...Wrong. TONS of stuff is visible from LEO. Do you think that
> >Manhattan or LA suddenly become invisible because you are 120 miles
> >up? Perhaps the Great Wall is the only object visible from the Moon
> or
> >somesuch distance.
> >
> BZZZZZT,BZZZZZZT WRONG WRONG WRONG.  8^)
>
>         The Great Wall of China is the only thing visible from space
>         with
>                 "the naked eye."

Should I say "Wrong again"? The real story of this myth is this:

On his mercury flight Gordon Cooper claimed that over Tibet (the
country) the air was so thin that he could see individual houses and
the smoke from the chimneys.... "Somehow out of this came the myth that
the Great Wall of China was espically visible, even though Gordo had
not flown far enough north to see it, and, a few years later, this
notion had grown to the point that it was suppose to be the only
man-made feature on earth visible from the moon, which I can attest is
certainly not the case."

Quote from "Liftoff" by Michael Collins (Apollo 11 astronaut) page 59.

>

-----------------------------------------------------------------------
Gene Kennedy - Ham Radio Operator, N5ABI - lobster.hou.tx.us!n5abi!gak
-----------------------------------------------------------------------

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

Date: 20 Jun 91 08:47:32 GMT
From: SUWATSON.STANFORD.EDU![e-mail]
Subject: Trying to contact oldtime SCI.SPACE people

In 1987 somebody named Adam J. Richter posted a message about L5, and I
wanted to reply. Unfortunately his return address of
jade!tart14.berkeley.edu![e-mail] didn't work for me.
Does anybody know how to reach that person?

In 1987 somebody (name unknown) posted a message about cleaning up
clutter in LEO, and I wanted to reply. Unfortunately his return address
of apollo![e-mail] didn't work for me. Does anybody know
how to reach that person?

In 1987 somebody named Jorge Stolfi posted a message about using
interstellar matter as fuel for reaching the stars, and I wanted to
reply. Unfortunately his return address of jumbo![e-mail]
didn't work for me. Does anybody know how to reach that person?

In 1988 somebody named Kevin B. Kenny [the Arch-Traitor] posted a
message about writing to Congresspeople regarding space (this was on
SPACE-ACTIVISTS, not SCI.SPACE, but I don't see that group in the list
of UseNet newsgroups), and I wanted to reply. Unfortunately his return
address of [e-mail] didn't work for me. Does anybody know how
to reach that person?

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

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Date: 20 Jun 91 06:55:33 GMT
From: ogicse!sequent!muncher.sequent.com![e-mail]
Organization: Sequent Computer Systems, Inc.
Subject: Earth-crossing water (was Re: Platinum-group..)
References: <[e-mail]>, <[e-mail]>, <[e-mail]>
Sender: [e-mail]
To: [e-mail]

In article <[e-mail]> [e-mail] (Paul Dietz) writes:

>Water should also be available on some class C asteroids, if
>carbonaceous chondrites are any indication (some contain significant
>water of hydration in their minerals).  If these meteorites are
>derived from earth-approaching asteroids, there would be no need to go
>to the outer solar system.  Water is also available on Mars.

As we continue to explore we may find much better sources. Several
short-period comets cross the orbit of Earth.  Comets are made
primarily of water ice, with significant amounts of carbon monoxide
and dioxide, methane, and other volatiles.  They give off dust as the
volatiles are vaporized by the Sun.

Comets are often associated with meteor showers, which contain
mostly dust sized particles but sometimes also larger objects that
produce fireballs.  The Tungaska event is believed to have been
caused by a 100,000 ton fragment from P/Encke.   Some fireballs
have been photographed even in daylight; one crossed over Wyoming on
August 10, 1972 and skipped back into space.

The Alpha Capricornids meteor shower features a large number of fireballs.
Fireballs associated with meteor showers do not end up as meteorites; they
are either volatile ice or very fragile conglomerations of dust and burn
up in the atmosphere.  There are also fireballs not associated with a
comet orbit; these can be carbonaceous, stony, or metal and produce
the meteorites.  As a side note, we may see some good fireballs from the
Alpha Capricornids this summer during July and August, since the parent
comet (something like P/Honda-Mrkos-Pjd from my abbreviated notes :-)
reaches perihilion at the end of this year.

Comets tend to break up.  We have observed more than twenty occurences
of comet fragmentation.  We can assume this is quite common.   What we
don't know is how fast these fragments evaporate.  If they are consumed
slower than they are replenished by new fragmentations, there could be a
significant number of ice-bearing bodies in orbits with favorable capture
trajectories.  The ice itself can provide reaction mass to simple
solar-thermal engines.  Most of the delta-v can come from Earth and
Lunar gravity assists.

It is also possible that some Earth-crossing asteroids are extinct
comets, and these may contain ice underneath the surface.  The
asteroid 3200 Phaeton is associated with the Geminid meteor shower stream,
for example.

Another note of interest is that the comet P/Griggs-Skjellerup, which
Giotto is planned to flyby in 1992, is associated with the Pi-Puppid
meteor shower.  This should give a good showing next April as GS
nears perihilion.

Overall, we haven't done nearly enough exploration to know where the best
sources of water and volatiles are to be found.

references:

_The Mystery of Comets_, Fred L. Whipple, 1985
_Comets_, Laurel Wilkening ed., 1982

appendix:

Here are some data on Earth-crossing ice and dust gleaned from _The
Cambridge Encyclopdia of Astronomy_ and similar sources:

_warning_: due to informal scholarship, the perihilion figures are
  +/- 2 months, at best.  Better figures solicited.

meteor showers and their parent bodies
--------------------------------------
                                                                        next
shower          max     range           ZHR     parent          period  peri
------          ---     -----           ---     ------          ------  ----
Quadrantids     Ja4   Ja1-5             100     ?               ?       ?
v Pi-Puppids    Ap24  Ap21-26            60     Griggs-Skje     5.2     Au 92
                                                                        Oc 97
d Beta Taurids  Jn29  Jn23 - Jl5         20     Encke           3.3     ?
f Alpha Capricornids
                Au1   Jl15 - Au25        10     Honda-Mrkos-Pjd 5.28    Ja 92
                                                                        My97
Perseids        Au12  Jl25 - Au18        70     Tuttle 2        ?       ?
v Draconids     Oc8   Oc7-10            "high"  Giac.-Zinner    6.52    Fe 91
                                                                        Oc 97
Orionids        Oc21  Oc6-27             35     Haley           73      2069
Taurids         No1   Oc10 - De5         12     Encke           3.3     ?
v Leonids       No17  No14-20            1,000  Tempel-Tuttle   33.3    Oc99
Geminids        De13  De8-16             60     3200 Phaeton    ?       ?
Ursids          De21  De17-25            5      Tuttle          13.6    Jn 94


ZHR = Zenith Hourly Rate
v = variable, ZHR for perihilion
d = daytime
f = fireballs


--
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.

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

End of SPACE Digest V13 #772
*******************