Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO315.TXT

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Date: Wed, 14 Oct 92 05:04:39
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #315
To: Space Digest Readers
Precedence: bulk


Space Digest                Wed, 14 Oct 92       Volume 15 : Issue 315

Today's Topics:
                   Controversy over V-2 anniversary
              Diesen sphere or Strungen Sphere (2 msgs)
                          Gallileo's antenna
                          HRMS/SETI Answers
         Math programs with arbitrary precision for the Mac?
NASA workshops on detection and interception (was Re: asteroid impact)
                               Roswell
                       SETI functional grammar
                       SETI functional grammer
the development and change of the soft-and-hardwsre programms for electronic computers and microcontrollers.
Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)
                Two-Line Orbital Element Sets, Part 2

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

Date: Wed, 14 Oct 1992 05:15:20 GMT
From: Henry Spencer <[e-mail]>
Subject: Controversy over V-2 anniversary
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Josh 'K' Hopkins) writes:
>>... they made some 65,000 modifications to delay
>>mass production.
>
>I've seen numbers like this too, but it's not clear to me whether they made
>so many modifications because they wanted to or because, never having built a
>ballistic missile, it took a few tries to get things right.

Actually, according to some of the more detailed histories, it was neither.
They were constantly having to revise the design because one material or
another featured in the original design had become unavailable.  They found
this frustrating, and said so.

However, it also appears to be true that they never did get complete and
final convergence on the build-test-analyze-revise cycle for the mass-
produced version.
--
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 00:19:05 GMT
From: Steve Linton <[e-mail]>
Subject: Diesen sphere or Strungen Sphere
Newsgroups: sci.astro,sci.space

|> 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.

However there is another problem. A rigid spherical shell cannot all be in orbit,
the poles would fall in. There are two solutions to this that I have heard

1) instead of  rigid shell you have a large number of small (asteroid like)
bodies in carefully arranged orbits. These can deply very thin solar collectors
like wings to ensure that no energy is allowed to escape.

2) have a VERY thin shell, supported by the light pressure inside and perhaps
passing power to external orbitting habitats. A 1AU shell for the sun would be
about 3 microns thick (if made of rock) and would mass no more than a medium
sized moon.

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

Date: 14 Oct 92 05:20:07 GMT
From: Henry Spencer <[e-mail]>
Subject: Diesen sphere or Strungen Sphere
Newsgroups: sci.astro,sci.space

In article <[e-mail]> [e-mail] (Josh 'K' Hopkins) 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.

So don't make it 1 km thick.

There really isn't any reason to make the thing any thicker than what you
need to hold atmosphere and provide shielding.  You're not going to get
any useful amount of gravity out of any practical thickness.

In practice, if you look at Dyson's *original* proposal, he wasn't
suggesting a solid one-piece sphere at all, partly because it presents
tremendous structural challenges.  He was proposing a swarm of smaller
bodies, each individually in orbit, which together would intercept almost
all of the output of the star.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 13 Oct 92 17:42:53 GMT
From: Douglas Stevens <[e-mail]>
Subject: Gallileo's antenna
Newsgroups: sci.space

Does anyone know if NASA has managed to get Gallileo's antenna
open yet?

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

Date: 14 Oct 92 02:27:09 GMT
From: Jeff Bytof <[e-mail]>
Subject: HRMS/SETI Answers
Newsgroups: sci.space

>From: [e-mail] (Al Guintu):

>Q: "WHAT IF ETI STOPS SENDING?"
>   what about a hypothetical eti civilization that stopped
>   transmission for example, because their government
>   cut off the resources for the work  ;->  ?  would the current
>   research ignore observation of the tail end of such a
>   transmission?

What if ETI sends brief signals at highly infrequent intervals?
For us to successfully receive such a signal, either we must
observe the sky omnidirectionally at all times, or somehow
guess the timing rule as a function of search direction.

A prudent and efficient ETI might transmit to us along the
following lines:

   1. They do not broadcast omnidirectionally,
      and not unless they have evidence the target
      system has a habitable planet.

   2. They are aware of the structure of our Solar System and
      the existence of Earth from their astronomical
      observations.

   3. They broadcast at a specific moment, guessable by us.

   4. The "guessable moment" or timing rule must determined
      by a (preferably) cyclical phenomena that we and they can
      both observe.

   5. The orbital motion of Jupiter can be used to construct
      a timing rule.  One possible mode: construct a vector
      from the Sun to Jupiter.  Then construct a vector from
      the Sun to a particular direction (towards a solar-type star,
      for instance).  Observe in that direction at times when the angle
      between the two vectors is a minimum, which occurs every
      11.86 years.  If ETI lies in the observed direction,
      their task is to send a signal to arrive at our Solar
      System when we are looking in their direction, as governed
      by the timing rule.

   6. ETI must have a "pretty good telescope"
      to get Jupiter's orbit and the distance to our Solar
      System nailed down well.  I assume
      that they are more advanced than we (a common assumption).

   7. There will be error in the arrival time of the signal,
      so ETI will have to set the length of the their transmission
      to match the expected error.  We know when to look
      with greater accuracy, and catch part of the message.
      If we aren't looking in the right direction at the right
      time, we can catch it later at modulo 11.86 year intervals.

   8. The information content of the message from ETI in this
      strategy might be limited to instructions for sending our
      reply.

   9. ETI can reduce the amount of time they listen for our reply
      by the instructions given in their message.  If they provide
      us with the values they've obtained for determining the
      orbit of Jupiter (the timing rule) and their estimate of
      the distance to our Solar System (which they get from
      long baseline astrometry), we can solve for a more precise
      value of the Solar System-ETI distance.  With a more
      precise distance value in hand, we can transmit a reply
      that it will arrive at ETI at an expected time.

  10. A major fault of this strategy is the assumption that ETI
      is local (they can see our Solar System).  If the number
      of communicating civilizations in the Galaxy is small,
      SETI is doomed if we are all "misers".  On the other
      hand, the "effective" number of communicating ETIs would be
      increased by dispatching automatic stations out into the
      Galaxy, placed in orbits counter-revolving with
      respect to the general Galactic rotation.  Such stations
      would drift along, mainly conducting passive astronomical
      observations of the Galaxy and transmitting data back to the home
      planet of the ETI.

  11. Being power limited, these stations could not act as omni-
      directional beacons, and a power-efficient strategy
      like the one presented here may be utilized.

  12. One automatic station may be followed by another.  If we
      are detected by the first, instructions could be beamed to
      the second to alter its cross-velocity slightly and intercept the
      Solar System ("A Bracewell Probe").

  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".

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







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

Date: 14 Oct 92 01:27:10 GMT
From: "Frederick A. Ringwald" <[e-mail]>
Subject: Math programs with arbitrary precision for the Mac?
Newsgroups: sci.space

In article <seal.719016011@leonardo>
[e-mail] (David Seal) writes:

>  other mac programs or ways of computing pi?

You mean like this?

N[Pi, 1000]
3.1415926535897932384626433832795028841971693993751058209749\

  4459230781640628620899862803482534211706798214808651328230\

  6647093844609550582231725359408128481117450284102701938521\

  1055596446229489549303819644288109756659334461284756482337\

  8678316527120190914564856692346034861045432664821339360726\

  0249141273724587006606315588174881520920962829254091715364\

  3678925903600113305305488204665213841469519415116094330572\

  7036575959195309218611738193261179310511854807446237996274\

  9567351885752724891227938183011949129833673362440656643086\

  0213949463952247371907021798609437027705392171762931767523\

  8467481846766940513200056812714526356082778577134275778960\

  9173637178721468440901224953430146549585371050792279689258\

  9235420199561121290219608640344181598136297747713099605187\

  0721134999999837297804995105973173281609631859502445945534\

  6908302642522308253344685035261931188171010003137838752886\

  5875332083814206171776691473035982534904287554687311595628\

  6388235378759375195778185778053217122680661300192787661119\

  590921642

This was done in about 4 seconds just now, read by me from a clock
on-screen, so it might be better, on a Mac II with 5 Megs of RAM, a
68030 chip with a 68881 coprocessor (which I'm not sure is even used),
under System 7.0.0 with virtual memory disabled, because it has never
worked on this machine - i.e., not the greatest Mac around, probably
slower than a new Classic II - with Mathematica 2.0.3 Enhanced.

It's no wonder Mathematica is rapidly emerging as the standard, at
least in academia. Not only was I able to redo all the math I had in
all of high school, college, and grad school in an afternoon (my
favorite command is still InverseLaplaceTransform[expr, s, t]), but
it's also frighteningly easy to use. Pricey, but well worth it, and no,
Steven Wolfram didn't pay me to write this. (Perhaps he should...)

E-mail me if you're interested in 10,000 or more places,
[e-mail]

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

Date: 14 Oct 92 05:19:17 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: NASA workshops on detection and interception (was Re: asteroid impact)
Newsgroups: rec.arts.sf.science,sci.space

In article <[e-mail]>, [e-mail] (Nick Szabo) writes:
> In article <[e-mail]> [e-mail] (Onno Meyer) writes:
>>I read a newspaper notice concerning an asteroid (or some other
>>kind of rock) passing the earth with ... million miles distance.
>>The paper said that a rock that would hit the earth could be deflected
>>with nuclear arms.
>
> [Nick's discussion of deflection problem deleted]
>
> A couple projects if funded could remedy our ignorance.
> These projects would cost only $70 million apiece, or in total
> 1/10 of 1% -- one-one-thousandth -- the cost of NASA's space
> station.  The first is Spacewatch, to find and track all dangerous
> earth-approaching asteroids.  The second would be a survey to use big
> telescopes and spectroscopy to determine the composition of these bodies.
> These projects are also critical to getting raw materials from these
> asteroids in the future, so we kill two birds with one stone (so to speak :-)

People seriously interested in these questions will want to get hold
of *The Spaceguard Survey: Report of the NASA International
Near-Earth-Object Detection Workshop*.  The group was chaired by David
Morrison of the University of Hawaii.  It met a number of times during
1991, and the report was released earlier this year.  I believe copies
can be obtained from NASA Headquarters in Washington; start by asking
the Public Affairs Office, NASA Headquarters, 600 Independence Avenue,
Washington, DC  20546 [phone].  To quote from the press release:

>     The NASA-sponsored Near-Earth-Object Detection Workshop
>judged asteroids with diameters 1 km or larger the most
>dangerous objects in terms of potential for causing catastrophic
>global effects on Earth.  Impacts of such asteroids are extremely
>rare and can be detected with current ground-based technology,
>most likely decades in advance of any collision.

Later, in January 1992, Los Alamos National Laboratory hosted a
Near-Earth-Object Interception Workshop.  This group worked on the
question of how to *prevent* asteroid collisions.  Their report isn't
out yet, having run into both political and budgetary problems (they
ran out of money to pay their editor).

Short overviews of both workshops, authored by some of their
participants, appeared in the May/June 1992 issue of *Mercury*, the
magazine of the Astronomical Society of the Pacific. They were
accompanied by an article by Fran Smith of the *San Jose Mercury
News*, "A Collision over Collisions: A Tale of Astronomy and
Politics."

According to Smith's account, Morrison persuaded Congressional
committees "that you didn't have to be a nut or a tabloid editor to
contemplate cosmic collisions."  Thus NASA's FY 1991 authorization
bill included a requirement to report to Congress on the asteroid
hazard; that's how these two workshops got started.

Smith describes a disagreement between Morrison and John Rather,
assistant director for space technology at NASA Headquarters, and a
member of the SDI community before he came to NASA.  Morrison's group
emphasized large objects, bigger than a kilometer in diameter, which
could cause regional or global cataclysm-- but which are eminently
detectable in ground-based telescopes.  Rather's group, which included
weapons physicists from Livermore and Los Alamos, was more interested
in objects 4 to 20 meters across-- hard to find with telescopes, but
more common, and easier to destroy or deflect with SDI-derived
technology plus nuclear weapons.

Names of such prominent SDI advocates as Edward Teller, Lowell Wood,
Roderick Hyde, and Gregory Canavan appear in the article, but it's not
clear to me who among them were actually involved with the
"Interception" workshop (Canavan was).  "Several months ago, after
several astronomers got their hands on a near-final draft calling for
`star-wars' technology and nuclear bombs," Smith writes, "they angrily
demanded that NASA revise these recommendations-- or drop their names
from the report."  She does not name these people, but long-time
opponents of SDI like Louis Friedman and John Pike are among the
members of Morrison's workshop.

My impression, from Smith's article, is that a number of specialists
in asteroid astronomy believe that organizing a search for possible
collisions is a good idea, but is difficult enough to sell without
getting connected to a weapons-development project.  Odds are that if
the search finds a large asteroid or comet due to collide with the
Earth, there will be years or decades of warning.  One could bet that
there would be plenty of time to develop a defense *after* such
detection.  Yet it might make sense to have collision-defense
development proceed in parallel with the search, at least at a modest
level.

In the same issue of *Mercury*, Gregory Canavan and Johndale Solem of
Los Alamos write in their summary, "Interception of Near-Earth
Objects:"  "The premiums for such insurance vary.  A few million
dollars per year could support observations and theory on detection
and interception.  A few tens of millions per year could provide
research on the technologies for interception, the dedicated
instruments needed to search for large Earth-threatening NEOs, and
research on the sensors needed to detect smaller asteroids at the
ranges desired.  A few hundred million dollars could develop and test
the robotic spacecraft missions needed to characterize NEOs of all
sizes.  Unfortunately, confusion over the relative priorities of
detection and interception has thus far delayed action on either,
although preliminary estimates indicate that either would justify the
research."

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

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

Date: 14 Oct 92 01:43:01 GMT
From: "Frederick A. Ringwald" <[e-mail]>
Subject: Roswell
Newsgroups: sci.space

In article <[e-mail]>
[e-mail] (Henry Spencer) writes:

> Come now.  If you're going to reprint stuff from Air&Space, [...]
> at least summarize the whole article, rather than taking part of it out
> of context.  Much the most interesting thing in that article was the
> observation that a crash of a hush-hush *US* project could easily account
> for the fuss and the secrecy... especially since the location was ideal for
> such a thing to happen.  Roswell is in the middle of an area that includes
> White Sands Missile Range, Los Alamos, and an airbase that then housed the
> world's only operational nuclear-bomber force.
>
> It's silly to invoke crashed UFOs when Earthly causes provide quite an
> adequate explanation.

It may well also explain the alleged "spook hangar" - number 19, if
memory serves me right - at Wright-Patterson AFB. I must say "alleged",
since I have not seen it myself, although I've heard one can see a
building that doesn't look like much. Let's see, a building that
doesn't look like much: now that's convincing!  ;-)

If such a building actually exists, and it does house something
dreadfully embarrassing to the USAF, you have your pick of nasties -
nuclear, chemical, or even biological - before you get to anything
extraterrestrial. Then there's the idea that's where the Arc of the
Covenant wound up... ;-) ;-) ;-)

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

Date: 14 Oct 92 04:45:10 GMT
From: John Roberts <[e-mail]>
Subject: SETI functional grammar
Newsgroups: sci.space

-From: [e-mail] (Josh 'K' Hopkins)
-Subject: Re: SETI functional grammer
-Date: 13 Oct 92 20:40:01 GMT
-Organization: University of Illinois at Urbana

-I ran across a thought experiment once where the prototype teleporting machine
-ends up on an alien planet and won't come back.  How do you tell the aliens
-to press the right (manual override) button and not the left (self destruct)
-button?  I couldn't figure a way out.

There's a way, but it involves some subtleties of nuclear physics - I don't
remember the details. You may have to assume the aliens are made of normal
matter rather than antimatter, but given that your machine didn't turn into
gamma rays, that's probably a pretty good assumption.

John Roberts
[e-mail]

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

Date: 13 Oct 92 23:42:12 GMT
From: Steve Linton <[e-mail]>
Subject: SETI functional grammer
Newsgroups: sci.space

Organization: U of Cambridge, England
Lines: 32
Nntp-Posting-Host: bootes.cus.cam.ac.uk
Source-Info:  Sender is really [e-mail]
Source-Info:  Sender is really [e-mail]


|>
|> Saying this is very hard is an understatement :-)  And rember that it may take
|> a few centuries to say "Sorry, I didn't catch that..."

What you don't do is wait for a response. Having found evidence of someone out
there, you send them everything you can think of, on every frequency you can
think of and just keep talking. After a few centuries they will (hopefully)
reply, and if they ask any questions you haven't already sent answers to you put
the answers in straight away. Even if it takes them decades to crack your
language it's a safe bet that they'll have recordede what you sent so far, so
they can go back and translate it all.

By all means send them clever codes and mathematics and so on, but also send them
encyclopedias and newspaper back issues and TV game shows. Who knows what'll be
the key to them cracking the language? Meanwhile of course we have to crack their
codes, mathematics, language and TV dating ads.

|>
|> I ran across a thought experiment once where the prototype teleporting machine
|> ends up on an alien planet and won't come back.  How do you tell the aliens
|> to press the right (manual override) button and not the left (self destruct)
|> button?  I couldn't figure a way out.

This is a fundamental physical problem. The easy answer is to refer them to some
assymetry in the machine, or in the distribution of quasars or something. Failing
that you can send them a helically polarised radio beam. Failing all those, you
have to describe a rather complicated piece of particle physics which
demonstrates that the universe is not symmetrical. I don't recall the details,
but it can be done (as long s you agree on the direction of time).

        Steve Linton

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

Date: 14 Oct 92 06:44:26 GMT
From: "Tahsin I. Alam" <[e-mail]>
Subject: the development and change of the soft-and-hardwsre programms for electronic computers and microcontrollers.
Newsgroups: sci.space,sci.research,sci.physics,sci.med,sci.engr.chem,sci.chem,sci.astro

Hi:

Is there any algorithm or any research paper on calculating volumes of
n-dimensional convex polyhedra? Any info would help.

I would appreciate it if you could send the reply directly to me at
the following address:

[e-mail]
Thanx,

--

ma'as-salama (Goodbye in Arabic, literally "With peace ... ")
Tahsin I. Alam

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

Date: 13 Oct 92 19:38:09 GMT
From: Bill Higgins-- Beam Jockey <[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] (Steve Linton) writes:
[uh-oh, Steve lost the antecedents, but he was referincing a Josh Hopkins(tm)
posting...]
> |> 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.
 [...]
> have a VERY thin shell, supported by the light pressure inside and perhaps
> passing power to external orbitting habitats. A 1AU shell for the sun would be
> about 3 microns thick (if made of rock) and would mass no more than a medium
> sized moon.

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 (in his previous life, before he achieved fame as Mr.
Dinky).

During the first and second stage         Bill Higgins
flights of the vehicle, if a serious      Fermi National Accelerator Laboratory
irretrievable fault should occur and      [e-mail]
the deviation of the flight attitude of   [e-mail]
the vehicle exceeds a predetermined       SPAN/Hepnet: 43011::HIGGINS
value, the attitude self-destruction
system will make the vehicle
self-destroyed.
     --Long March 3 User's Manual
     Ministry of Astronautics, People's Republic of China (1985)

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

Date: Wednesday, 14 Oct 1992 09:00:24 CET
From: [e-mail]
Subject: Two-Line Orbital Element Sets, Part 2
Newsgroups: sci.space

Sorry, but we are in mid of october and the last state of EUVE is again
for august 19th.  Is it not anymore tracked by NORAD?

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Thorsten Nedderhut             |  Disclaimer:
mbp Software & Systems GmbH    |
c/o ESA/ESOC/FCSD/OAD/STB      |  Neither ESA nor mbp is responsible
Darmstadt, Germany             |  for my postings!
[e-mail]           |

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

End of Space Digest Volume 15 : Issue 315
------------------------------