Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_7/V13_753.TXT

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Subject: SPACE Digest V13 #753

SPACE Digest                                     Volume 13 : Issue 753

Today's Topics:
             Re: == No Subject ==
               == No Subject ==
               Re: Dark matter
              Space electronics
  Re: Platinum-group metal concentrations in earth-crossing objects
              microsat tracking
              The other side of the sun
              Re: Microgravity?
             Solar sails and Belt mining
           Re: Solar sails and Belt mining
             Re: == No Subject ==
               Mining El Dorado
          help on Henyey_Greenstein phase function ?

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
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  should be sent to [e-mail], or, if urgent, to
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----------------------------------------------------------------------

Date: 16 Jun 91 17:44:16 GMT
From: agate!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!ptimtc!nntp-server.caltech.edu![e-mail]  (David Palmer)
Subject: Re: == No Subject ==

[e-mail] (Mary Shafer) writes:
>You're quite incorrect.  I asked Gordon Fullerton (you know, STS-2, etc)
>about this and he said that the Great Wall isn't even visible in LEO.
>However, quite a few man-made structures are visible from LEO, including
>dams, airports, freeways in the deserts, and cities.

>Dave Scott (Apollo 15) once told me that the only man-made thing he
>could see from the moon was city lights at night and even those were
>pretty dim.

Probably the easiest manmade thing to see from space is the Sahara Desert.
(This desert is the result of domestic animals under human control,
e.g. goats, eating away the vegetation at the periphery, allowing
the desert to spread.)

--
        David Palmer
        [e-mail]
        ...rutgers!cit-vax!gap.cco.caltech.edu!palmer
    "Operator, get me the number for 911"  --Homer Simpson

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

Date: 16 Jun 91 12:59:22 GMT
From: mcsun!ukc!slxsys!ibmpcug!demon![e-mail]  (Ian Stirling)
Subject: == 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."

        Steve

___________________________________________
kuwait?
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------------------------------

Date: 17 Jun 91 01:59:31 GMT
From: att!cbfsb!cbnewsb.cb.att.com![e-mail]  (robert.f.casey)
Subject: Re: Dark matter


This thought crosses my mind on the topic of dark matter:  There can't be
much of any sort that we are not familiar with in the solar system.  Or else
the laws of Gravitation that Newton discovered would be confused. If the solar
system was imbedded in a sea of unusual dark matter, calculations on the
interactions between planets wouldn't work out right.  Maybe further out there
is some dark matter to explain the deviations of Neptune that prompted the
search that found Pluto.
There can't be much in the inner solar system, or else our space probes,
satellites and moons would travel on paths that wern't correctly predicted.

Any of you rocket scientists in the know have comments?

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

Date: Sun, 16 Jun 91 09:36 EDT
From: [e-mail]
Subject: Space electronics
X-Envelope-To: [e-mail]

I'm interested in the technical details of various space craft sensors and
electronics. Are the schematics and circuit details of the electronics
available? I'm curious how the particle sensors and various field detectors
operate.  Can anybody point me to a good reference?

Michael B. Hayden
[e-mail]
[e-mail]

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

Date: 16 Jun 91 23:41:10 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!wuarchive!cs.utexas.edu!ut-emx!nowhere![e-mail]  (Steven King)
Subject: Re: Platinum-group metal concentrations in earth-crossing objects


   Of course, all of this presumes that even if you were to get
 there and the processes were viable, that the asteriod is yours
 to mine. International law, as I understand it, is less than clear
 on this issue.  A few billion in precious metals might buy a lot
 of influence, but it would also buy a lot of envy.



--
If it don't stick, stink, or sting
It ain't from Texas.
                                        ..!cs.utexas.edu!ut-emx!nowhere!sking

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

Date: 16 Jun 91 12:59:26 GMT
From: mcsun!ukc!slxsys!ibmpcug!demon![e-mail]  (Ian Stirling)
Subject: microsat tracking

>>retrofitting standard,$5,000 satellite dishes.Can somebody comment
>>on what it takes to get a standard TV satellite dish to track a
>>low-earth-orbiting satellite?
>
>Basically a new mount and more powerful motors and realtime tracking
>software running on a personal computer. The polar mount used
>on home dishes gives limited continous sky coverage in a tracking

Why would it need more powerful motors? Arn't most mounts designed
for reasonably rapid change between different satelites ,surely all
that would be needed is a cleverer or re-programmed driver?

Mail to either                            |PLEASE do not send large
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------------------------------

Date: 16 Jun 91 19:12:37 GMT
From: agate!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu!zaphod.mps.ohio-state.edu!caen!hellgate.utah.edu!csn!scicom![e-mail]  (Bruce Watson)
Subject: The other side of the sun


Is there a spacecraft out there on the other side of the sun from
us that could tell if there are any large spots like the one
now just rotating off the face?
--
|              |   One hundred thousand people is the optimum         |
| wats@scicom  |   population for a world in which the work will be   |
|              |   done by robots. -- Arthur C. Clarke                |

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

Date: 14 Jun 91 21:59:21 GMT
From: aio!ecfa![e-mail]  (Michael C. Matthews)
Subject: Re: Microgravity?

In article <[e-mail]> [e-mail] (joefish) writes:
>
>After visiting the 500 foot vacuum zero gravity at NASA Lewis
>Research Center in Cleveland in 1968, I found several facts
>very interesting.
>
>The drop time is about 5 seconds, but they have a spring loaded
>slingshot that throws the package up to the top, giving about
>10 seconds total zero (near zero) gravity.    This facility
>...
>Joe Fischer        uunet!coplex!disk!joefish

Darn! He gave it away!  And I thought I was gonna make a bundle going around
to all those drop facilities as a consultant, telling them how they can cheaply
double their microgravity time...   :-)


--
Mike Matthews                   |        [e-mail]
Tethered Vehicle Analysis Group | (backup) -->  [e-mail]
Advanced Projects Section; Navigation, Control, and Aeronautics Department
Lockheed Engineering & Sciences Company,  Houston, Texas,   [phone]

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

Date: 16 Jun 91 12:59:17 GMT
From: mcsun!ukc!slxsys!ibmpcug!demon![e-mail]  (Ian Stirling)
Subject: Solar sails and Belt mining

If you can make a workable solar sail how much more difficult is it
to make a large parabolic mirror for melting large boulder size
chunks of rock? Could you mine a asteroid my melting it and allowing
the vapour that comes off to condense on nearby cooled surfaces,using
a sort of fractional distilation to seperate the metals.Also could
you get higher temperatures than the surface of the sun by filtering
the incoming light at the mirror(diffraction grating ?)to leave only the
higher energy photons,this does not seem to violate any laws as you
are only able to use a small fraction of the incoming light to heat
the object but most of the light goes past at lower overall energy.

Mail to either                            |PLEASE do not send large
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------------------------------

Date: 16 Jun 91 00:19:01 GMT
From: van-bc!rsoft!mindlink![e-mail]  (Nick Janow)
Subject: Re: Solar sails and Belt mining

Non-imaging optics could also improve the thermal efficiency of generators.
They could possibly turn a working fluid into plasma, driving an MHD generator.
This needs a fair bit of work in developing large-scale non-imaging optics and
in developing thermal radiators for use in space (though the techniques should
work here just as well).  I wonder how such a system would compare with other
solar generation schemes.
--

[e-mail]

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

Date: 16 Jun 91 16:50:27 GMT
From: swrinde!elroy.jpl.nasa.gov!news.arc.nasa.gov!skipper![e-mail]  (Mary Shafer)
Subject: Re: == No Subject ==


In article <[e-mail]> [e-mail] (Ian Stirling) writes:

   #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."

You're quite incorrect.  I asked Gordon Fullerton (you know, STS-2, etc)
about this and he said that the Great Wall isn't even visible in LEO.
However, quite a few man-made structures are visible from LEO, including
dams, airports, freeways in the deserts, and cities.

Dave Scott (Apollo 15) once told me that the only man-made thing he
could see from the moon was city lights at night and even those were
pretty dim.

I've been to the Great Wall and it's not very big, it's tan, and the
chaparrel grows right up to it.  I think you'd be hard-pressed to see
it from 40,000 ft, let alone LEO.

--
Mary Shafer  [e-mail]  ames!skipper.dfrf.nasa.gov!shafer
           NASA Ames Dryden Flight Research Facility, Edwards, CA
                     Of course I don't speak for NASA
            "Turn to kill, not to engage."  CDR Willie Driscoll

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

Date: 16 Jun 91 19:51:53 GMT
From: bu.edu!rpi!usc!srhqla!denwa!stb![e-mail]  (Charles (from bbs))
Subject: Mining El Dorado

How do we mine the El Dorado asteroid ?  Is it one big stainless steel
nugget, or is it differentiated ?  Either way, I propose blasting it
to pieces using high explosives.  If it is a homogeneous stainless
steel nugget I would drill a hole right to the center and insert a
small nuclear  device.  If it is differentiated, conventional
explosives might suffice.  Nuclear gives more bang per pound, so
better than chemical and takes less propellant to send it to El
Dorado.
     We do not want lots of fragments flying everywhere, all we need
     is to create a powerful shock wave to disrupt the asteroid structure.
     The shock should be small enough that gravity will continue to hold
     the pieces together.   We could literally surround the asteroid with a
     safety net to ensure most of it is retained.    Once shocked the
     pieces can be individually transported or processed by a robot
     smelter.   If it is well differentiated it might be possible to
     visually separate out nuggetts of rare metals, and discard the
     silicates and iron.    A weak acid could dissolve reactive metals (
     alkali earth and alkali metals and iron ) and heavier metals like Gold
     and Platinum would be beneficiated.    If desired the acid solution
     could be electrolysed with low energy to recover the lighter metals.
     Beneficiating by weight might be possible, would have to spin the
     nuggetts in a centrifuge to find out how dense they are.   Each nugget
     could also be scanned by alpha particle back scattering or other
     radio-spectroscopy  means, and then sorted into valuable and less
     valuable bins. Probably cheaper than electrolysis too.  Most efficient
     might be to use minimum size ( ie critical mass only ) nuclear
     charges, and progressively shock parts of El Dorado, that allows more
     margin for error in case we guess wrong about the quantity of shock
     needed - do not want to over do it !    Would need rather a lot of
     diamond drills if it is steel, maybe somebody could design a laser
     cutting torch so we can burn our way in.   How about a deliberate
     nuclear pile meltdown on the surface, the hot pile melts to the center
     via gravity - al la China Syndrome.
        An advantage of a single blast dead center would be that the
        surface structure would be least affected, so it might be possible to
        the centre, and leaving a large hollow structure which could be turned
        into a human habitat.  I like that better than progressively blasting
        it completely to pieces from the outside.   Residual radiation might
        be a problem for future colonists, I wonder what the half-life would
        be.
           In the immediate term it would be interesting to send a probe to
           El Dorado,  to see if it is differentiated or homogoneous.
           El Dorado is probably spinning, so the blast could be timed such
           that the exhaust coming out of the drill hole would cause a reaction
           which would tend to propel the asteroid towards the Earth a little.
           We do not have controlled fusion, but maybe a large thermonuclear
           device could be designed as a shaped charge.   After the initial
           fission explosion and hollowing out some of the interior, the
           thermonuclear shaped charge could be inserted into the interior of El
           Dorado, and the drill hole widened.   The blast would then be mostly
           directed out through the vent hole, creating a more substantial thrust
           reaction, which could maybe manouver El Dorado within a few million
           miles of Earth.   This would be most useful if the blast could be done
           at perihelion, thus lowering the aphelion, making collection of the
           asteroid pieces much cheaper.
               Perhaps the nuclear shocking and thrusting could be a government
               program.   Then collection and benefaction of the pieces could be by
               private prospectors.

            * Origin: Ventura Co NSS 805-649-5314 STS final approach
            (1:206/2403.0)


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

Date: 16 Jun 91 08:37:22 GMT
From: agate!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!spool.mu.edu!munnari.oz.au!uniwa!cc.curtin.edu.au![e-mail]
Subject: help on Henyey_Greenstein phase function ?

I am working on atmospheric correction of NDVI. I need some help about the
appropriate values of rural aerosol Henyey-Greenstein phase function asymmetry
parameters to use in my work. The only values I am able to find are for marine
aerosol. I will be very pleased for your help.

Paul Mathaha
Curtin University of Technology,
Physics Department,
GPO Box U1987
Perth, W.A. 6001

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

End of SPACE Digest V13 #753
*******************