Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO317.TXT

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Date: Thu, 15 Oct 92 05:01:30
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #317
To: Space Digest Readers
Precedence: bulk


Space Digest                Thu, 15 Oct 92       Volume 15 : Issue 317

Today's Topics:
                                <None>
              Diesen sphere or Strungen Sphere (3 msgs)
                             Dyson sphere
                          HRMS/SETI Answers
  Lecture Summary: What if SETI Succeeds, myth that we're prepared (
         Math programs with arbitrary precision for the Mac?
           Math progs with arbitrary precicion, for UNIX...
                   Pres Debate & military spending
           Sally Ride info please (1st female US Astronaut)
                             Telepresence
Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere) (3 msgs)
                              VSA: Help!
                         what use is Freedom?

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", and (un)subscription requests of the form
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----------------------------------------------------------------------

Date: 14 Oct 92 11:07:59 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: <None>
Newsgroups: sci.astro,sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
> In article <[e-mail]> [e-mail] (Bill Higgins-- Beam Jockey) writes:
>>I doubt whether 3 microns is enough to be reasonably opaque, let alone
>>a nearly perfect reflector
>
> Bill has lost three orders of magnitude here...  Drexler made 50nm (I think
> it was) aluminum that was an excellent reflector.  Around 30, I believe, it
> starts to become transparent.

As Arthur Clarke once said, what's a factor of 10**3 among friends?

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

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

Date: 14 Oct 92 17:14:29 GMT
From: Henry Spencer <[e-mail]>
Subject: Diesen sphere or Strungen Sphere
Newsgroups: sci.astro,sci.space

In article <[e-mail]> [e-mail] (Greg Hennessy) writes:
>#You're not going to get
>#any useful amount of gravity out of any practical thickness.
>
>You're not going to get *ANY* gravity out of it, NO MATTER how thick
>you make it. The gravitational force on the inside of a sphere is
>zero...

Use the outside, not the inside.  Arranging indirect lighting is left
as an exercise for the student. :-)

However, the original point remains valid, alas...  There isn't enough
mass available in the solar system to get useful gravity (enough to
hold an atmosphere, say).
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 14 Oct 92 22:27:28 GMT
From: Josh 'K' Hopkins <[e-mail]>
Subject: Diesen sphere or Strungen Sphere
Newsgroups: sci.astro,sci.space

[e-mail] (Steve Linton) writes:

>>A Dyson sphere with a radius of one A.U. (as postulated in the Start Trek
>>episode to which the poster refered - it's also a nice round number) and 1 km
>>thick would require about 10e17 cubic km of materials.
>>
>>Earth has a volume close to 10e12 cubic km. Jupiter is about 100 times bigger.
>>
>> Where is there enough stuff to build out of?

>The answer of course is that you don't build it 1km thick. Using all the available
>matter we get about 1m thick, which would be plenty to plate solar collectors on.
>Indeed a metre of solid rock, spread out would make plenty of levels of low-g
>living space.

But here's where I pull the ace out of my sleeve.  The vast majority of the
solar system isn't rock.  It's hydrogen, helium and other stuff not especially
well suited to construction.  And we've ignored the question of atmosphere.

--
Josh Hopkins                                          [e-mail]
     The views expresed above do not necessarily reflect those of
ISDS, UIUC, NSS, IBM FSC, NCSA, NMSU, AIAA or the American Association for the
                      Advancement of Acronymphomaniacs

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

Date: Thu, 15 Oct 1992 00:08:14 GMT
From: Steve Linton <[e-mail]>
Subject: Diesen sphere or Strungen Sphere
Newsgroups: sci.astro,sci.space

|>
|> >The answer of course is that you don't build it 1km thick. Using all the available
|> >matter we get about 1m thick, which would be plenty to plate solar collectors on.
|> >Indeed a metre of solid rock, spread out would make plenty of levels of low-g
|> >living space.
|>
|> But here's where I pull the ace out of my sleeve.  The vast majority of the
|> solar system isn't rock.  It's hydrogen, helium and other stuff not especially
|> well suited to construction.  And we've ignored the question of atmosphere.

This is of course true, but building a rigid Dyson sphere has enough other
problems that a little transmutation (just fuse all the hydrogen and helium to
carbon and oxygen - as a bonus you get some energy to help with the construction
work) seems minor.

All Dyson really observed was that a really advanced civilization might be
expected to be using  (somehow) all the energy of their star, and re-radiating it
as waste heat (necessarily from a larger surface) and that it might be worth
looking for 'stars' that were big and cool in this way.

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

Date: 14 Oct 1992 21:48 -0700
From: Donald Arseneau <[e-mail]>
Subject: Dyson sphere
Newsgroups: sci.astro,sci.space

In article <[e-mail]>, [e-mail] (Steve Linton) writes...

% I don't think you want a reflective Dyson sphere, for reasons discussed
% much further back in the NewsGroup (you cook the inner planets). For a
% loss of 50% of your lift you can make do with a black one which also
% enables you to convert all the solar energy into something useful (Dyson's
% original reason for proposing the sphere).

But the light bounces around to the other side and will still get absorbed
eventually.  If the sphere is 80% reflective, there will be 4 x 2 = 8
times the pressure as for a black sphere.

But what about the sun in the center?  I think the outer layers would heat
up a lot. Would that cause a huge solar wind?  Anyone want to speculate?

Donald Arseneau       [e-mail]

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

Date: 14 Oct 92 15:49:09 GMT
From: Jeff Bytof <[e-mail]>
Subject: HRMS/SETI Answers
Newsgroups: sci.space

>From: [e-mail] (Jeff Bytof):

>  13. The content of the initial communication would be limited
>      to the purely functional requirements of signal timing.
>      The content of our reply (determined by the ETI)
>      may be required to be a simple "password" that advances
>      the "conversation" to the next level.  If we can decode
>      their instructions for proper content and timing for our
>      reply, we have passed the "first test".

14. The "second test" would be the long, long wait for the
"conversation" to continue in greater depth or for a "visitation"
to occur.  Sagan and others have proposed that just the discovery of
ETI would extend the lifespan of our civilization.  Also observe
how long Christians have been waiting the the Second Coming.

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

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

Date: 14 Oct 92 22:03:33 GMT
From: David Dick <[e-mail]>
Subject: Lecture Summary: What if SETI Succeeds, myth that we're prepared (
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Gary Coffman) writes:

>In article <[e-mail]> [e-mail] (stuart goldman) writes:
>> an automobile.  Look at the amount of recklessness and stupidity that occurs
>> on a daily basis there.  Between drunk driving, speeding (not that I have
>> never speeded) and deaths on the road on a daily basis, and that's in two
>> dimensions.  What would happen if everyone had access to an airplane?  Then
>> they're succeptable to collision in three dimensions... then deal with space

>The reason there are so few midair collisions is not the superhuman pilots,
>sober as judges, or the omnipotent FAA. The reason is it's a lot harder to
>hit something with three degrees of freedom than something confined to
>two dimensions, and further confined by roads. It's the difference between
>hitting a sitting duck and a duck on the wing. As we move into space, the
>miss distances grow huge.

However, you'd still have the problems at places where craft concentrate:
docking/landing places (analogous to airports, which have near misses
from time to time) and volumes where trajectories get squeezed
together because of two-body gravity and common destinations (analogous,
perhaps, to VORs that everyone vectors in to and out of).

David Dick
Software Innovations, Inc. [the Software Moving Company]

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

Date: 14 Oct 92 17:48:02 GMT
From: David Seal <[e-mail]>
Subject: Math programs with arbitrary precision for the Mac?
Newsgroups: sci.space

[e-mail] (David Seal) writes:

>Having been duly inspired by an episode of northern exposure i tried
>fiddling with ramanujan's and borwein and borwein's formulas for
>computing pi on my mac.  however, the floating point accuracy
>for MATLAB (which i was using) isn't settable and i can't get past
>the sixteenth decimal place or so.  other mac programs or ways of computing
>pi?  thanks.

so sorry.  my %$@#(*^) nn software has been confusing me.  should have been
to sci.math.

ds
--
-----------------------------------------------------------------------------
David Seal                 |  Jet Propulsion Laboratory  |     sunset: 7:54pm
[e-mail] |       Mission Design        |   temp: 82 degrees

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

Date: 15 Oct 92 03:07:20 GMT
From: "Frederick A. Ringwald" <[e-mail]>
Subject: Math progs with arbitrary precicion, for UNIX...
Newsgroups: sci.space

In article <[e-mail]>
[e-mail] ("Phil G. Fraering") writes:

> You mean you're not going to gratuitously post them?

Any more aggravation of this kind, and I'll post the calculation to
50,000 places that just finished, all 130K of it!   ;-)

It took about 2.5 hours. As I was saying, it isn't the fastest machine
in town. By the way, there are versions of Mathematica that run under
UNIX, and most other common operating systems.

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

Date: 13 Oct 92 15:53:39 GMT
From: Mark Ricci - CATS <[e-mail]>
Subject: Pres Debate & military spending
Newsgroups: talk.politics.space,sci.space

[e-mail] writes:
>In yesterday's presidential debate all three candidates agreed that if we are
>to cut defense spending, we better start retraining and retooling so that money
>is not wasted and jobs are not lost.  Perot in partiuclar said that the
>conversion from military hardware should be to some other high technology... it
>is hard to convert from potato chips to computer chips in time of war
>(paraphrase)  Well, we all know (at least those of us who read these groups)
>that one of the technologies that is most closely related to the military is
>space.  It is time to get the word out.  We have to let the next administration
>know that one of the most logical (and probably easiest) transformations would
>be from military hardware to space hardware.  In fact many of the people
>working on one are working on the other

Transforming the defense contractors into space contractors, which many of
them are anyway, is no transformation at all.  You're simply substituting one
government nipple for another.  The companies need to get away from the
government, not latch onto another part.

>The possibilities are there... spy-technology to remote sensing, hypersonic
>research to civilian aircraft, etc.  All these seem painfully obvious, in fact
>almost too ovbious to be brought up.  But the fact is that it is not really
>happening, defense workers are loosing their jobs, and the space budget is
>going down.  Take a recent example, to save jobs Bush agreed to sell F15 to
>Saudi Arabia, a highly contraversial decision.  How about if to save those same
>jobs the same money had been used for a space program tha M-D might be involved
>in.  Some of the money goes to retraining, some to the actual project.  It
>sounds logical, but it is not being done.

The transformation should be for these high-tech firms to produce high-tech
products that the marketplace wants, not just the federal government.  This is
how the expertise and the training they have can be put to the best use for
them and for us.  Making space doodads instead of military doodads is not the
solution no more than selling weapons for the sake of keeping defense workers
employed in key states is.

This is not to say that they shouldn't make space doodads.  They should, and
there'd be a market outside the Beltway if the government didn't consider space
closed to private concerns.  Nevertheless, to remain dependent on the goverment
is a sure prescription for disaster.

>It is time to move, or we will loose our chance to rip the benefits of the much
>talked about 'peace dividend.'

When you have a $400 billion deficit and a $4 trillion debt, there is no
peace dividend, just bills due.

Mark
--
===============================================================================
 Mark Ricci - CATS          | Four candidates are on the ballot in al l 50
 Commodore Applications and | states, yet only three are invited to debate.
 Technical Support          |
 [e-mail] |    Why are they scared of the Libertarians?
===============================================================================

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

Date: 14 Oct 92 11:57:02 GMT
From: Andrew Finegan <[e-mail]>
Subject: Sally Ride info please (1st female US Astronaut)
Newsgroups: sci.space

Hi Folks,
     My 12 year old daughter has asked me for help in preparing a
a profile of Sally Ride, the USA's first female (and youngest) astronaut.

Any details, and particularly any references to (easily) accessable
publications will be gratefully received.

Please mail your replies directly to me.

If there is any interest, I will post the final profile to this group.

Thanking you in advance,

Cheers

Andrew

ANDREW FINEGAN   (Standard Disclaimers)     | RMIT Centre for Remote Sensing
Email : [e-mail]         | PO Box 12182, A'Beckett Street
Phone : [phone]   Fax : [phone]   | Melbourne Australia 3000
----------------------------------------------------------------------------
"... I was to learn later in life that we tend to meet any new situation by
reorganizing; and a wonderful method it can be for creating the illusion
of progress while producing confusion, inefficiency and demoralization."
                                        Petronius, AD 60

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

Date: 14 Oct 92 17:38:35 GMT
From: Willie Smith <[e-mail]>
Subject: Telepresence
Newsgroups: sci.space

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

>an experienced operator of a
>lunar rover might be able to maintain continuous motion much of the time,
>so the phantom would be continually in sight.)

After an hour or two of driving my simulated lunar teleop vehicle
around, it's easy to do the 'forward estimation' in your head and
anticipate enough to move at a few feet per second.  Of course it
helps to have a bit of leeway, and any tricky stuff quickly
degenerates into "move-wait-move", but the human brain is pretty
adaptable.  Don't drive or operate heavy machinery immediately
afterwards though. :+)

Willie Smith
[e-mail]

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

Date: Wed, 14 Oct 1992 15:34:15 GMT
From: Henry Spencer <[e-mail]>
Subject: Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)
Newsgroups: sci.astro,sci.space

In article <[e-mail]> [e-mail] (Bill Higgins-- Beam Jockey) writes:
>I doubt whether 3 microns is enough to be reasonably opaque, let alone
>a nearly perfect reflector (which you want when building a solar
>sail.)  I don't have a handbook handy, but I think you need dozens of
>microns of aluminum to make a good reflector.  Eric Drexler ran into the
>transparency problem when he was trying to design the most lightweight
>possible sail...

Bill has lost three orders of magnitude here...  Drexler made 50nm (I think
it was) aluminum that was an excellent reflector.  Around 30, I believe, it
starts to become transparent.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 14 Oct 92 23:08:21 GMT
From: Henry Spencer <[e-mail]>
Subject: Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)
Newsgroups: sci.astro,sci.space

In article <[e-mail]> [e-mail] (Nick Haines) writes:
>What's the solar wind pressure at 1AU?

Negligible compared to the photon pressure.  (Now that's small...)
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: Wed, 14 Oct 1992 23:33:32 GMT
From: Steve Linton <[e-mail]>
Subject: Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)
Newsgroups: sci.astro,sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
|> In article <[e-mail]> [e-mail] (Bill Higgins-- Beam Jockey) writes:
|> >I doubt whether 3 microns is enough to be reasonably opaque, let alone
|> >a nearly perfect reflector (which you want when building a solar
|> >sail.)

I don't think you want a reflective Dyson sphere, for reasons discussed much
further back in the NewsGroup (you cook the inner planets). For a loss of 50% of
your lift you can make do with a black one which also enables you to convert all
the solar energy into something useful (Dyson's original reason for proposing the
sphere).

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

Date: 14 Oct 92 11:44:11 GMT
From: "Voevodin S.A." <[e-mail]>
Subject: VSA: Help!
Newsgroups: sci.space

 Dear Sir,

 If you are able please help me! Can you answer my questions:

 1. Do you have a List of all flights of 'Europa' space launcher?
 2. A. Fisher is in the Astronaut detachment, isn't he? What skandal did
    take place?
 3. When did D.Slayton retire from NASA astronaut team?
 4. What satellites should have been launched by Indian ASLV-1 and 2 space
    boosters?
 5. When and what Chinese Landing capsules should have returned to the Earth?
 6. "TRW Space Log 1957-1991" gives a launch booster for 1970-09 TAT-Delta-
    Agena D. What kind of booster is it? What does it look like?
 7. "NASA Rocket Statistics. January 1978", the only source, said that the
    first lunar Subsatellite was launched from  Apollo-14. Is it true or
    just a misprint?
 8. Why was the spaceship where Grissom, White and Chaffee burned dead in
    1967, called Apollo-1 though Apollo-1-3 flied before 1967?
 9. Apollo AS-206, 207, 208 flied to the Skylab spacestation, Apollo AS-210
    flied fulfilling ASTP, where is Apollo AS-209 then?
10. What construction differences are there between Atlas E, Atlas F and
    Atlas H space launchers?


Sergey A. Voevodin

[e-mail]

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

Date: 14 Oct 92 16:23:41 GMT
From: "Michael V. Kent" <[e-mail]>
Subject: what use is Freedom?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Andy Cohen) writes:
>In article <[e-mail]>, [e-mail]
>(Richard Whitmeyer) wrote:
>
>> OK, I do have some questions,
>>
>> 4.   Can I too see or experience the mockups? How about my kids.

How do I sign up?

>LETS KEEP THE THREAD GOING!

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 !!

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

Newsgroups: sci.space,sci.astro

From: Nick Haines <[e-mail]>
Subject: Re: HRMS/SETI Answers
In-Reply-To: [e-mail]'s message of Wed, 14 Oct 1992 16:14:18 GMT
Message-Id: <[e-mail]>
Originator: [e-mail]
Sender: Usenet News System <[e-mail]>
Nntp-Posting-Host: voila.venari.cs.cmu.edu
Organization: School of Computer Science, Carnegie Mellon University
References: <[e-mail]>
    <[e-mail]>
Date: Wed, 14 Oct 1992 22:38:25 GMT
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Source-Info:  Sender is really [e-mail]

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

   Why can't HRMS detect a current earth-like technology leakage at
   interstellar distances? Isn't this the most likely case?

Why is this the most likely case? We can't assign any probabilities to
levels of technology or power use by ETs. If we just look at human
history, we've been putting out _any_ signals for less than 100 years
and current levels for only a few decades. Any guesses on what powers
we'll be putting out (and at what frequencies) in 2092? 2992? 11992?
How directional will our signals be? What about our interstellar
probes?

I guess the reason HRMS wouldn't pick up BBC1 at 4 light-years is the
same reason why it won't spot a dim light-bulb at 4 gigaparsecs:
money.

(and it _would_ pick up military radar at ~5 light-years).

Nick Haines [e-mail]

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

End of Space Digest Volume 15 : Issue 317
------------------------------