Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO320.TXT

Internet Message Format | 1993-07-13 | 28KB

Date: Fri, 16 Oct 92 05:03:20
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #320
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri, 16 Oct 92       Volume 15 : Issue 320

Today's Topics:
                      Candidates' Forum on Space
                       Cosmic strings (2 msgs)
                             Dyson sphere
                     Gallileo's antenna (3 msgs)
                           Luna 10 (2 msgs)
           Math progs with arbitrary precicion, for UNIX...
                          NASA town meetings
               Pres Debate & military spending (2 msgs)
                       SETI functional grammer
Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", and (un)subscription requests of the form
    "Subscribe Space <your name>" to one of these addresses: listserv@uga
    (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle
    (THENET), or [e-mail] (Internet).
----------------------------------------------------------------------

Date: 14 Oct 92  09:47:02
From: [e-mail]
Subject: Candidates' Forum on Space
Newsgroups: sci.space

Inland Empire NSS Chapter Holds Congressional Candidates' Forum

  On Saturday, October 3, the Inland Empire Space Group, a chapter
of the National Space, hosted a forum on aerospace issues at the
Riverside Central Library in downtown Riverside. Attending the
forum were candidates for the 42nd and 43rd congressional
districts, or their representatives.
  The Democratic candidate for the 43rd district, Mark Takano,
pushed for conversion of California's aerospace industry to
non-military applications, such as production of fuel cells and
electric cars. He did not consider civil space to be a major
component of this conversion process.
  The representative for Republican candidate Ken Calvert (R-43),
Bob Woolf, stated that the nation's security requires a
continuing need for a strong military. He also expressed support
for funding for NASA, although not in concrete numbers.
  Candidate Dick Rutan (R-42) declined to attend or send a
representative.
  Congressman George Brown, a candidate for the 42nd district and
current Chair of the House Committee on Space, Science and
Technology, was unable to attend, but was represented by Temoc
Figueroa, his campaign Field Director. Mr. Figueroa did not
provide specifics during his discussion, except to restate Mr.
Brown's commitment to the eventual development of human colonies
in space. The timetable for these settlements would be subject
to today's stringent budget constraints. However, Mr. Brown's
office did provide specific answers to questions posed by the
Inland Empire space Group prior to the debate. Included in the
responses were support for the Space Exploration Initiative, HR
3848, the Competitiveness in Space Act, the Launch Service
Purchase Act, a positive resolution on U.S. use of former Soviet
space hardware, and commented that NASA should not be
responsible for development of the Delta Clipper.
  The Libertarian candidates in the 42nd and 43rd districts, Fritz
Ward and Gene Berkman agreed that NASA, as a government agency
should be abolished, and that private industry should take up
the slack from a drastically reduced Department of Defense.
  Some members of OASIS, the Los Angeles chapter of the National
Space Society, and the Inland Empire Space Group, will meet in
the Riverside area on Saturday, October 31, to participate in
the campaign for the 42nd district. For more information on this
event, or on the positions of these candidates, please contact
David Anderman at 714/524-1674.






--- Maximus 2.00

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

Date: 15 Oct 92 17:46:19 GMT
From: "Wm. Douglas Withers -- math  FACULTY <[e-mail]>" <[e-mail]>
Subject: Cosmic strings
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Justin Smith) writes:
>
>Are any cosmic strings known (or believed) to exist?
>--
There's a woman down the hall from me who does research on cosmic string
theory.  She says no.

--
Els Withers                   email: [e-mail]
Department of Mathematics     phone: [phone] / fax: [phone]
United States Naval Academy
Annapolis, MD  21402-5002     Senri no tabi mo ippo yori...

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

Date: 15 Oct 92 10:50:22 GMT
From: [e-mail]
Subject: Cosmic strings
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Justin Smith) writes:
>
> Are any cosmic strings known (or believed) to exist?

No, there are no cosmic strings known to exist. The discovery of one would be a
momentous achievement and would revolutionise cosmology, astronomy and much of
theoretical physics.

The is one possible object (or rather association of objetcs) which has been
suggested to be a cosmic string. This is a series of 'double galaxies' which
may be gravitationally lensed pairs strung along the string. Paper in Ap J Lett
by Esther Hu and Len Cowie a couple of years ago. No one really believes in
this, and I think redshift measurements may have since ruled it out.

There may still be a number of searches looking for strings based on similar
associations currently underway.

The best way to see if strings exist at the moment os to see what their effect
on galaxy formation and large scale structure were in the early universe, and
this is all tied up with cosmological models etc etc. Chances of a resolution
to these problems in the near future are not great IMO.


Dave

--
================================================================================
Dave Clements, Oxford University Astrophysics Department
================================================================================
clements @ uk.ac.ox.vax            |  Umberto Eco is the *real* Comte de
dlc      @ uk.ac.ox.astro        |           Saint Germain...
================================================================================

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

Date: 16 Oct 92 05:05:49 GMT
From: John Roberts <[e-mail]>
Subject: Dyson sphere
Newsgroups: sci.space

-From: [e-mail] (Donald Arseneau)
-Subject: Dyson sphere
-Date: 15 Oct 92 04:48:00 GMT
-Organization: TRIUMF: Tri-University Meson Facility

-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?

Christopher Neufeld and I worked part of that out some time ago. A completely
black sphere would receive twice the influx of energy per unit area as a
nonenclosed object the same distance from the sun, and net outward photon
pressure 1.5 times as great. Both these numbers would go up for a partially
reflective sphere. A perfectly reflecting sphere would eventually explode.

A black sphere surrounding the sun at 1AU would have an outer surface
temperature of about 140 degrees Celsius (pretty hot - for a temperature
of 25 C you'd want the radius to be about 1.9AU), and would heat the surface
of the sun only a fraction a degree. A reflecting sphere would be *hotter*
and would heat the sun more. To make the calculations more interesting, try
a sphere that's reflective on the inside and black on the outside.

The net photon pressure on a partially reflective sphere might depend on
whether the reflectance of the inner surface is diffuse or specular.
Has anybody worked on that?

I'll try a few more calculations, based on the simplifying assumption that
a given substance is equally reflective at all wavelengths (generally not
true). Then if you assign each substance a reflectance rating of N (where
0 = black and 1 = perfectly reflective), and if you only consider diffuse
reflection, then for a sphere of a uniform substance, the incident radiation
on the inner surface is 2/(1-N) times the normal flux at that distance
from the star, the net photon pressure is 0.5 + 1/(1-N) times the normal
amount, and the temperature of the outer surface will be (1-N)^0.25 times
the temperature of a black sphere of the same dimensions, with the
temperature measured in kelvins. For instance, with N of 0.9 (90% reflectance,
pretty good for a silver reflector, and probably not too far off for an
aluminum reflector), the incident flux on the inner surface would be 20
times the normal amount, the net photon pressure would be 10.5 times the
normal amount, and the temperature of the outer surface (1AU) would be about
470 degrees Celsius. To get back down to 25 C, you'd have to set the radius
to about 6AU.

John Roberts
[e-mail]

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

Date: Fri, 16 Oct 1992 01:14:53 GMT
From: Adrian Hassall Lewis <[e-mail]>
Subject: Gallileo's antenna
Newsgroups: sci.space

As far as I know it hasn't been fixed; and on that assumption, I want
to ask a question that is probably a FAQ.

Would it be feasible to send a small robot after Gallileo that would
clamp itself onto antenna pole and then push in the pins that are
holding the ribs shut?
I can see several problems - revendous (damn, how do you spell it?), and
making an antenna small enough for the robot.
However, it also seems to me that control is not a problem as you wouldn't
need real time control.  This also seems a helluva lot simpler than sending
an entirely new high-gain antenna.

Adrian

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

Date: 16 Oct 92 05:07:34 GMT
From: Henry Spencer <[e-mail]>
Subject: Gallileo's antenna
Newsgroups: sci.space

In article <u926135.719198093@tasman> [e-mail] (Adrian Hassall Lewis) writes:
>Would it be feasible to send a small robot after Gallileo that would
>clamp itself onto antenna pole and then push in the pins that are
>holding the ribs shut?

Basically, no.  It's beyond the current state of the art, never mind
the available time and money.

(If you doubt the first part of that statement, consider that just the
"clamp on" part has been tried three times -- Solar Max, Palapa/Westar,
and Intelsat -- and has failed *all three times*.)

If we were going to send something after Galileo, by far the simplest
approach -- and the only one that got serious consideration -- would be
to simply send a relay satellite to accompany Galileo to Jupiter.  There
is no problem sending data from Galileo at high speed if the receiver
is nearby (and it doesn't have to be all that close, most any Jupiter
orbit would probably do).
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 16 Oct 92 04:04:07 GMT
From: Steve Linton <[e-mail]>
Subject: Gallileo's antenna
Newsgroups: sci.space

In article <u926135.719198093@tasman>, [e-mail] (Adrian Hassall Lewis) writes:

|> Would it be feasible to send a small robot after Gallileo that would
|> clamp itself onto antenna pole and then push in the pins that are
|> holding the ribs shut?
|> I can see several problems - revendous (damn, how do you spell it?), and
|> making an antenna small enough for the robot.
|> However, it also seems to me that control is not a problem as you wouldn't
|> need real time control.  This also seems a helluva lot simpler than sending
|> an entirely new high-gain antenna.

A whole range of fixes based on extra space-flights have been proposed, some to
fix Gallilileo as it comes past Earth, others to dispatch a communications relay
to Jupiter to retransmit high-speed telemetry from Gallileo's LGA. All
essentially foundered on the problem of designing a new piece of hardware and
getting it ready to fly in the available time. Anything intended to work near
Jupiter would also have had to be nuclear powered and the generators needed are
in very short supply, and would have to survive the very hostile environment
around Jupiter.

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

Date: 15 Oct 92  08:00:10
From: [e-mail]
Subject: Luna 10
Newsgroups: sci.space

There has much speculation recently about the possibility of ice in deep
craters at the poles of the Moon. There are two means of determining
whether primeval ice exists at these locations: 1) searching all polar
craters, either by robotic rover or astronauts, or 2) use of remote
sensing instruments in polar lunar orbit.

No spacecraft equipped with a gamma spectrometer has ever orbited over
the poles of the Moon, according to those who propose that the USA
undertake a new lunar mission that would carry scientific instruments
into a polar lunar orbit.

However, the Soviet Union launched a spacecraft that carried a gamma
spectrometer into a polar lunar orbit (71 degrees inclination), back
in 1966. Has anyone ever seen the data from this instrument? I presume
that the Soviets didn't bother to look for lunar ice back in the 1960's.




--- Maximus 2.00

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

Date: 16 Oct 92 05:00:20 GMT
From: Henry Spencer <[e-mail]>
Subject: Luna 10
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>However, the Soviet Union launched a spacecraft that carried a gamma
>spectrometer into a polar lunar orbit (71 degrees inclination), back
>in 1966. Has anyone ever seen the data from this instrument? ...

I doubt that this was a gamma-ray spectrometer in the sense that the term
is now usually used, i.e. something useful for surface mapping.  If it was,
the data has never been released; Lunar Sourcebook, the authoritative
source on virtually everything known about the Moon, doesn't even mention
Luna 10.

In any case, 71 degrees is not good enough.  The inclination needs to be
a full 90 degrees.  A gamma-ray spectrometer is not an imaging instrument;
the data you get is from the surface more or less directly under the
spacecraft.  The incidence of permanent shadow drops sharply once you're
more than a few degrees from the pole; lunar slopes are gentle.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 16 Oct 92 04:47:10 GMT
From: Henry Spencer <[e-mail]>
Subject: Math progs with arbitrary precicion, for UNIX...
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (FRANK NEY) writes:
>Where can I get a DOS or OS/2 version of Mathematica?  Keep in mind
>that I do not have FTP.

FTP wouldn't help.  Mathematica is commercial software.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 15 Oct 92 18:59:31 GMT
From: Alex Howerton <[e-mail]>
Subject: NASA town meetings
Newsgroups: sci.space

In article <8OCT199217131401@utrcv1> [e-mail] writes:
>The following blurb was pointed out to me from a recent Aerospace Daily:
>
>   NASA HAS selected six cities around the U.S., including Hartford, CT, for
>   town meetings in which individuals and businesses can offer their views on
>   the future direction of the nations civil space and aeronautics programs.
>
>Since I'm pro-space and in the Hartford area, I'd like to go and put in
>my $.02.  Can anyone tell me what I need to do in order to attend?
>Useful info includes: date/time/place, how to register (if necessary),
>who to contact.
Yes, I live in Seattle, and I read here that one of the meetings is going to
be here. If anyone who knows could post or e-mail the dates, times, and
locations, for all six of the meetings, I for one would appreciate it.

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

Date: 15 Oct 92 19:12:08 GMT
From: Alex Howerton <[e-mail]>
Subject: Pres Debate & military spending
Newsgroups: talk.politics.space,sci.space

>Here is something which I think the space community should start pushing for
>very soon.
>
>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
>(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
I wrote Clinton a detailed two-page letter on how to convert from defense
to space spending, and the benefits it could bring. I got absolutely no
personal response. He kept asking for money, however.
>| Carlos G. Niederstrasser        |   It is difficult to say what   |
>| Princeton Planetary Society     | is impossible; for the dream of |
>|                                 | yesterday, is the hope of today |

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

Date: 16 Oct 92 03:40:16 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Pres Debate & military spending
Newsgroups: talk.politics.space,sci.space

In article <[e-mail]> [e-mail] (Mark Ricci - CATS) writes:
>[e-mail] writes:
>>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.

Unfortunately, the aerospace industry is ill equipped to operate when
separated from the government teat. There's little consumer demand for
$800 toilet seats, or $120 million dollar ex-ballistic missiles. The
companies don't have a clue how to make $19 Walkmans, or even $2 million
dollar sewage treatment plants. Their corporate culture isn't setup to
handle such concepts. A much reduced Boeing might survive on airliner
sales, but have you looked at the airline industry lately? They aren't
in a position to be buying a lot of airplanes. If the government money
goes away, these companies, and their military capabilities, are going
to go away. Perot's right, they can't be just thrown on the consumer market,
they'll die.

>>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 Saudis don't seem interested in spending their money on space hardware.
They want fighter planes and they're willing to pay top dollar. No US
government money is involved in the F15 sale, so there's no money to be
diverted to space.

>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.

The question is, though, just what high tech consumer goods do these
companies know how to produce, and more importantly, *market*? And,
how much of their military capabilities will they preserve for the
day when the world heats up again, as it will? We're told that an
Iowa class battleship can't be built today because no company has
the technology to do it. It's been lost as the shipyards and steel
companies have converted to civilian markets. We're told that we
can't rebuild the Saturn V because the subcontractors went bankrupt
during the funding cuts of the 1970s. Can we afford to let this happen
to our aerospace companies?

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

Actually the Federal government is in better shape than most consumers.
They spend 35% of their income servicing the debt. How many of you
spend less than 35% of your incomes on house notes, car notes, and
consumer debt? The US government owes four times it's annual income.
How many of you living in $200,000 houses and driving $40,000 cars
can say you owe less?

Gary

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

Date: 16 Oct 92 00:42:05 GMT
From: Steve Linton <[e-mail]>
Subject: SETI functional grammer
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Robert J Woodhead) writes:
|> [e-mail] (Josh 'K' Hopkins) writes:
|>
|> >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.
|>
|> Describe it in terms of physical properties, including the RIGHT-HAND
|> rule.
|>

Unfortunately, the right-hand rule depends on our conventions for which way
current flows and which way a magnetic field points. The former can be
established (provided we know whether our aliens are matter or anti-matter) but
the latter cannot. Electromagnetism actually is mirror-symmetric.

There are bits of particle physics which are asymmetric. Provided we know our
aliens are matter, then we can ask them to observe the beta-decay of cobalt-60
nuclei in a magnetic field. More of the electrons emerge going North than South
(or vice versa I forget). If we don't know that the aliens are matter an even
subtler experiment is needed, but there is one.

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

Date: 15 Oct 92 17:32:47 GMT
From: Bill Cornette <[e-mail]>
Subject: Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)
Newsgroups: sci.astro,sci.space

Paul Dietz ([e-mail]) wrote:
: 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.
:
: I believe the skin depth of aluminum at optical wavelengths is in
: the tens of nanometers.  You can reduce the mass still further by
: drilling holes << 1 wavelength in diameter.


What wavelength did you have in mind -- admittedly, you can assume that
most of the solar energy is less that 4-5 microns, but there is still quite
a lot of solar flux down below 0.2 microns -- and remember the lower the
wavelength, the higher the frequency and the more energic the photon.
    Maybe you can figure out a way to drill holes << 0.1 micron (or
so) but I wouldn't enjoy doing it.

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


Received: from VACATION.VENARI.CS.CMU.EDU by isu.isunet.edu (5.64/A/UX-2.01)
    id AA21537; Fri, 16 Oct 92 01:02:44 EDT
Received: from crabapple.srv.cs.cmu.edu by VACATION.VENARI.CS.CMU.EDU
          id aa03768; 16 Oct 92 0:50:37 EDT
To: [e-mail]
Newsgroups: sci.space
Path: crabapple.srv.cs.cmu.edu!cantaloupe.srv.cs.cmu.edu!das-news.harvard.edu!spdcc!think.com!rpi!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!usenet.ins.cwru.edu!agate!stanford.edu!eos!millard
From: Millard Edgerton <[e-mail]>
Subject: Re: Math programs with arbitrary precision for the Mac?
Message-Id: <[e-mail]>
Organization: NASA Ames Research Center
References: <seal.719016011@leonardo> <[e-mail]>
Distribution: usa
Date: Thu, 15 Oct 1992 23:06:20 GMT
Lines: 44
Sender: [e-mail]
Source-Info:  Sender is really [e-mail]

[e-mail] (IGOR) writes:

>In article <seal.719016011@leonardo>, [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.


>a very simple way of computing pi is as follows:
>pi/4=4*atan(1/4)+atan(1/239) i may actually mess up the argument in front
>of the atan so you would have to check on a calculator.

>The fancy thing about this instead of using pi=4*atan(1),  one can expand
>the atan in term of series atan =x -x^3/3+x^5/5-x^7/7 with a radius of
>convergence of r=1, which means it this specific case that the acceleration of
>convergence will be tremendous if you are using arguments less than 1 such as
>1/4 and 1/239. With this formula, the problem of finding pi is to develop
>routines doing subtraction,addition and division of infinitely long numbers...\
>which is a problem that one probably solved in sixth grade...
>I think that after the third term computed i was able to get a seven digit
>accuracy... not bad




>Igor
>Texas A&M University
>--------------------------------------------------------------------------
>Its a nice bike
>    terminator 2
>-----------------------------------------------------------------------------

The solution of 355/113 yields PI to with 10^-7.  Archemedies knew it close
enough for our use today, beyond that it is an academic exercise.

***************************************************************************
* When I examine myself and my methods of   | Standard disclaimers apply  *
* thought, I come to the conclusion that the| Millard J. Edgerton, WA6VZZ *
* gift of fantasy ment more to me than my   | [e-mail]    *
* talent for absorbing positive knowledge. A. Einstein                    *
***************************************************************************

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

End of Space Digest Volume 15 : Issue 320
------------------------------