Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO319.TXT

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Date: Fri, 16 Oct 92 05:02:03
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #319
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri, 16 Oct 92       Volume 15 : Issue 319

Today's Topics:
                                <None>
             Arbitration in Action on the Extropians List
                   Bootstrap hardware for LunaBase
                             Dyson sphere
            Galileo's antenna (was Re: Gallileo's antenna)
                      Galileo Update - 10/15/92
                          HRMS/SETI Answers
           Math progs with arbitrary precicion, for UNIX...
                      Query Re: pluto direct/ o
                       sub Juan Carlos Vazquez
                       Thickness of a reflector
Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere)
                      Ulysses Update - 10/15/92
                           Uploaders' fate

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Date: 15 Oct 92 23:31:10 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: <None>
Newsgroups: sci.space,sci.astro

In article <[e-mail]>, [e-mail] (Keith Harwood) writes:
[continuing a discussion on sci.space about engineering at the Moon's
poles]
>
> In article <[e-mail]>, [e-mail] (Bill Higgins-- Beam Jockey) writes:
> . . . Put manufacturing plant at the Lunar north pole.
> . . .
>> mirrors on a tall tower can give you power 28 days around the clock
>> there, too.)
>
> I was under the impression that the moon's axis had much
> the same obliquity to the ecliptic as the Earth's, so either
> you have very tall towers or six month's light and six
> month's dark.

No, the Moon's axis is tilted only 1.5 degrees to the ecliptic, so at
its poles a little elevation will put you in perpetual sunlight.

> (If the moon's axis was normal to the ecliptic
> we would get about 28 degrees of north-south libration and
> I'm sure it's only about five degrees.)

I can't yet answer this paradox.  While I am scribbling little diagrams
here, can anybody else explain it?

Bill Higgins          |  If we can put a man on the Moon, why can't
Fermilab              |  we put a man on the Moon? -- Bill Engfer
[e-mail] |  If we can put a man on the Moon, why can't
[e-mail]   |  we put a woman on the Moon? -- Bill Higgins

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

Date: Thu, 15 Oct 92 18:51:48 EDT
From: Tom <[e-mail]>
Subject: Arbitration in Action on the Extropians List

>This is a private mailing list. It isn't run by a government -- its
>run by The Extropy Institute (aka ExI), which has set up private rules
>and regulations regarding its use. Part of its rules call for people
>to behave in a civilized way, and provide for mechanisms, all private,
                ^^^^^^^^^
>to deal with people who don't behave that way. The way in which self

Is it even possible to behave in an uncivilized way, while typing on a
highly complex electronic machine, communicating (if you want to
call it that) with others in a common language, sometimes over vast
distances?

I mean, we can't hit each other over the computer, right?

-Tommy Mac
------------------------------===========================================
Tom McWilliams               | Those who beleive        ' are the  ".   |
[e-mail]       | in the      ,  .        .  ones  .*'  .  |
[phone] -or- 353-2986 | Balance   '. '  . .        that , don't  |
a scrub Astronomy undergrad  |   of            ,        +         get   |
at Michigan State University | Nature                  '.  , .' eaten   |
------------------------------===========================================

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

Date: 15 Oct 92 21:53:34 GMT
From: "Edward V. Wright" <[e-mail]>
Subject: Bootstrap hardware for LunaBase
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Nick Szabo) writes:

>>You snub comm sats in favor of mining the asteroids.

>Huh?  Not at all.  I promote them both.

Nonsense.  You can't promote both: that violates Nick Szabo's Law.
Anyone who wants to do anything *more* than launching comm sats is
"snubbing" them.  You've accused other people of that over and over
again, letting only yourself off the hook, by special dispensation.


>Furthermore, I think that
>asteroid mining missions (and the volatile extraction missions that
>will likely precede them) should use the same launchers as comsats,
>instead of demanding their own special-purpose hardware.

Instead of designing specialized launchers for different tasks, let's
try to make one vehicle do all possible jobs?  The same mistake NASA
made with the Shuttle.  Those who ignore history are condemned to
repeat it.


>That's one big reason why comsats and the military are so important.

What?  You want the military to pay your way?  If anyone else said
that, Nick, you'd accuse them of socialism.


>I have a big problem with proposals like SSF and FLO that soak up
>huge chunks of the budget in their own enclosed, built-from-scratch world,

The budget that you want for your "private, free-enterprise" projects?


>I've dreamed up over a dozen original concepts which I've posted here,
>while you repeat ancient dogma.  I've got you beat cold in the
>imagination category. The issue here is the economic validity of these
>plans,

Yeah, you can say that again. :-)


>Automated volatile extraction requires good controls and high
>reliability.  It does not require "AI"

Right.  It does not require AI because AI is not good enough.
What the job does require is a self-repairing, self-adapting system
with good dexterity and unparalleled pattern recognition capabilities.
There is only one system that meets those requirements today --
Homo sap, Mark I, Mod 0 -- with no replacement in sight, despite
your claims to the contrary.


>the definition of which seems to be "the hard problems" -- as soon as
>they're solved they're no longer AI.

That definition was someone's *joke*, Nick.  Maybe you should
try taking an AI course some day and get some idea what you're
talking about.

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

Date: Thu, 15 Oct 1992 16:02:58 GMT
From: Stan Bischof <[e-mail]>
Subject: Dyson sphere
Newsgroups: sci.space

In sci.space, [e-mail] (Donald Arseneau) writes:

>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.

Hmm. I'm a little late in this discussion, so please excuse me if I am
not interpreting your statement incorrectly, but huh, what?

Are you looking at the difference in kinetic energy transfer (i.e light
pressure) between a perfectly absorbing surface (inelastic collision) and
a reflecting surface (elastic collision)?

If so then would you care to explain how the difference can ever be
more than a factor of 2, since a perfectly elastic collision imparts
exactly twice the energy as a perfectly inelastic collision?
(unless you are using flubber, of course!)

i.e how does %80 reflective become   4x2=8 times the pressure?
    Shouldn't this be more like 1.8 times the pressure?

Stan Bischof
HPSR

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

Date: 16 Oct 92 00:17:19 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: Galileo's antenna (was Re: Gallileo's antenna)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Douglas Stevens) writes:
> Does anyone know if NASA has managed to get Gallileo's antenna
> open yet?

Boy, this is becoming a Frequently Asked Question in sci.space... I'll
have to prepare something to add to the FAQ files.

The answer is "no."  They are still trying cooling turns.  Below is an
excerpt from a Galileo mission summary I recently wrote for science
teachers.  (Keep it around, and we can all mail hundreds of copies to
the next person that asks this question...)  It owes a lot to Jon
Leech's notes from the 11 June briefing, and to the videotape that
Ross Doyle of Fermilab made for me.  Thanks again, guys.

     THE ANTENNA PROBLEM

A number of "cooling turns" have been performed, where the antenna
mast is pointed so it's in the shadow of the spacecraft.  As it cools
off, the mast shrinks a little, and the antenna ribs have to bend
more.  Putting a strain on the ribs like this, over and over again,
may "walk" the stuck pins out of the sockets on the antenna mast.  At
least, that's what the computer models say. So Galileo will continue
to perform cooling turns every couple of months.

In December 1992 and January 1993, Galileo will be closer to the Sun
than it ever will be again, and hence warmer.  At this time cooling
turns will have their maximum effect.  Galileo engineers will combine
these with "hammering" the deployment motor, turning them on and off
thousands of times.  This will increase the force on the stuck ribs,
and gives the best hope of success in nudging them loose.

If the HGA still fails to open by next March, planners will begin to
follow a plan to complete the mission without it.

     WHAT HAPPENS IF IT DOESN'T OPEN?

The High-Gain Antenna can transmit from Jupiter and Earth at rates up
to 110,000 bits per second.  The Low-Gain Antenna is designed to
transmit at only 10 bits per second.  If Galileo has to get along
without the HGA, its operators will have to get very clever.  Here are
the steps planned:

--Improvements in ground antennas:  The Deep Space Network will
install better amplifiers at the Canberra, Australia station, better
receivers at all stations, and will combine several dishes together to
support a bit rate of up to 100 bits/second through the LGA.

--Data compression:  Galileo has multiple computers aboard.
"Stealing" the spare attitude control computer, JPL can program it to
process image data and "squeeze" it so that a picture can be
represented by 5 to 10 percent of the usual number of bits.  Tricky
algorithms allow them to do this without serious loss of image
quality.  Data compression is a hot topic in computer science on Earth
today-- for instance Compuserve's Graphical Interchange Format (GIF)
makes use of it.

--Error-correcting codes:  Software will be installed aboard the
spacecraft to encode data in better formats that are resistant to
errors or noise. This will enable Galileo to transmit at a higher data
rate where errors are more likely. (The modem on your computer
probably uses error-detecting or error-correcting codes.)

--Flyby vs. coasting:  It has always been planned that Galileo will
spend  short periods doing close flybys of the Galilean moons,
followed by long, slow loops (typically one or two months, sometimes
longer) around Jupiter before the next flyby.  If data are crammed
into the tape recorder during a week or so during a satellite
encounter, Galileo can take several weeks to process and transmit the
results to the ground.  It will be possible to get nearly as much
science done as with the original mission, where the satellites are
concerned. But some other aspects will not do as well.

The first major Galileo mission objective is direct measurement of
pressures, temperatures, chemistry, and other properties of Jupiter's
atmosphere when the probe parachutes into the giant planet.  This will
happen on Day One of the orbiter's Jovian orbit-- 7 December 1995.
The probe will transmit its findings to the orbiter during its
75-minute lifetime.  The orbiter can manage to store all this
information on its recorder and play it back using only the Low-Gain
Antenna, so this part of the mission can be accomplished despite the
handicap.

The major sacrifice will be frequent coverage of Jupiter itself--
atmospheric scientists were hoping to make detailed and extensive
movies of the planet's weather, wind circulation, color changes, and
so forth.  Since the total number of pictures will be reduced, these
studies will suffer.

The majority of Galileo's instruments produce a fairly modest stream
of bits, compared to the cameras.  So data that are not pictures, such
as magnetic and particle measurements or ultraviolet spectra, should
be fairly manageable, and most of the original objectives of these
experiments should be met.

The Galileo science team estimates that despite the loss of the HGA,
about 70% of the scientific objectives of the mission could still be
met-- given hard work by many people on planet Earth over the next few
years.  And who knows?  The antenna might open after all.  Keep an eye
on the news.

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

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

Date: 16 Oct 92 08:31:51 GMT
From: Ron Baalke <[e-mail]>
Subject: Galileo Update - 10/15/92
Newsgroups: sci.space,sci.astro,alt.sci.planetary

Forwarded from Neal Ausman, Galileo Mission Director

                                  GALILEO
                      MISSION DIRECTOR STATUS REPORT
                                POST-LAUNCH
                           October 9 - 15, 1992

SPACECRAFT

1.  On October 9, the Energetic Particle Detector (EPD) motor maintenance
exercise was performed which stepped the motor through its eight operating
positions and then returned it to Sector O which is the predicted least
contamination position in preparation for the execution of TCM-15 (Trajectory
Correction Maneuver #15). The motor maintenance exercise was successfully
verified by Memory Readout (MRO) commands.  Additionally, the EPD was returned
to Sector 4 at the completion of the maneuver.

2.  On October 9, the Trajectory Correction Maneuver (TCM-15) was performed
on the spacecraft.  The maneuver used the spacecraft's axial (z) thrusters and
lateral thrusters to impart a predicted total delta velocity of 0.72 m/s.
This maneuver was executed at 1200 bps with the spacecraft pointed
approximately 16 degrees off the Earth.

     The spacecraft's performance throughout the activity was normal.  All
RPM (Retro-Propulsion Module) pressures and temperatures and attitude control
indicators were near predicted levels.  After the axial and lateral burn
segments, the sequence planned spin corrections and pointing corrections were
not needed.

     Preliminary radio tracking data indicates a 0.5 percent overburn for the
axial segment and a 1.2 percent overburn for the lateral segment.

3.  On October 10, the Dual Drive Actuator (DDA-4) memory sequence load was
uplinked to the spacecraft without incident. This sequence load covers
spacecraft activities from October 12 to October 16 (see Special Topic No. 2).

4.  On October 10, Delayed Action Commands (DACs) were sent to the spacecraft
to switch from 40 bps uncoded telemetry to 1200 bps coded telemetry on
October 12 just prior to initiation of the DDA-4 sequence memory load.

5.  On October 12, real-time commands were sent to change the System Fault
Protection (SFP) AACS-INIT (Attitude and Articulation Control Subsystem)
pointing slot from the Earth to the Sun prior to the Dual Drive Actuator
(DDA-4) pulse activities.  This change will allow the spacecraft to return to
a sun-pointed attitude if an AACS Power on Reset (POR) occurs during the
DDA-4 pulse activities (see Special Topic No. 2).

6.  On October 12, cruise science Memory Readouts (MROs) were performed for
the Extreme Ultraviolet Spectrometer (EUV).  Preliminary analysis indicates
the data was received properly.

7.  On October 12, the DDA-4 memory sequence load went active.  The warming
turn to a 45-degree off-sun attitude started at approximately 2313 UTC and
completed 28 minutes later at 2341 UTC (see Special Topic No. 2).

8.  On October 14, Delayed Action Commands (DACs) were sent to turn off the
Plasma Detector supplemental heater after the sun acquisition to eliminate a
30-degree thermal cycle on the instrument.

9.  On October 14, after approximately 46 hours at the warming attitude, real
time commands were sent to enable the High Gain Antenna (HGA) Dual Drive
Actuator (DDA) motor primary relays, pulse the motors 10 times with an on time
of 0.267 seconds followed by an off time of 0.534 seconds, and then safe the
primary relays and reset the command loss timer.  The DDA motor temperature
was approximately plus 23.5 degrees C at turn on.  DDA motor current data
analysis is in progress.  Preliminary analysis indicates the motor current
during the 10 pulses was less than the stall current of 970 milliamps,
indicating some ballscrew rotation took place.

     Additionally, the spacecraft under stored sequence control was commanded
back to a 5 degree off-sun attitude at approximately 2345 UTC.  After the sun
acquisition, sun gate data was collected to determine if an antenna rib is
still obscuring the sun gate signal.  Preliminary data analysis indicates that
the sun gate field of view is still obscured, indicating no ribs released;
analysis is continuing.  Also, preliminary doppler tracking data collaborates
the sun gate data results.

10. On October 15, as part of the Dual Drive Actuator (DDA) No. 4 pulse
activities, real-time commands were sent to checkout the star scanner.  This
activity was performed as a precaution to protect the star scanner from
"seeing" bright particles which could release if an HGA rib released
(see Special Topic No. 2).

11. The AC/DC bus imbalance measurements exhibited some change. The AC
measurement has ranged from 12DN to 18DN and now reads 18 DN (4.1 volts).
The DC measurement has ranged from 117 DN (13.6 volts) to 141 DN (16.6 volts)
and now reads 129 DN (15.1 volts).  These measurement variations are
consistent with the model developed by the AC/DC special anomaly team.

12. The Spacecraft status as of October 15, 1992, is as follows:

       a)  System Power Margin -  56 watts
       b)  Spin Configuration - Dual-Spin
       c)  Spin Rate/Sensor - 3.15 rpm/Acquisition Sensor
       d)  Spacecraft Attitude is approximately 5 degrees
           off-sun (leading) and 19 degrees off-earth (lagging)
       e)  Downlink telemetry rate/antenna-1200 bps (coded)/LGA-1
       f)  General Thermal Control - all temperatures within
           acceptable range
       g)  RPM Tank Pressures - all within acceptable range
       h)  Orbiter Science- UVS, EUV, DDS, MAG, EPD, and HIC are
           powered on
       i)  Probe/RRH - powered off, temperatures within
           acceptable range
       j)  CMD Loss Timer Setting - 264 hours
           Time To Initiation - 263 hours

GDS (Ground Data Systems):

1.  Galileo Earth 2 Ground Data System (GDS) testing was conducted on October 6
and October 13, 1992 with the Galileo D1.0 ground system utilizing the MCCC
(Mission Control and Computer Center) real-time systems and the DSN (Deep Space
Network) Canberra Signal Processing Center (SPC 40).  Test objectives were to
validate the successful integration of the Galileo D1.0 ground system with the
DSN and MCCC system that will be used to support the Earth 2 activities.
Real-time analysis indicated all objectives were successfully met, however
some post-test analysis of data is on-going in the MTS and PFOE areas.

TRAJECTORY

     As of noon Thursday, October 15, 1992, the Galileo Spacecraft trajectory
status was as follows:

    Distance from Earth         31,353,400 miles (.34 AU)
    Distance from Sun           121,071,200 miles (1.30 AU)
    Heliocentric Speed           63,400 miles per hour
    Distance from Jupiter        611,760,500 miles
    Round Trip Light Time        5 minutes, 42 seconds


SPECIAL TOPIC

1.  As of October 15, 1992, a total of 8324 real-time commands have been
transmitted to Galileo since Launch.  Of these, 3367 were initiated in the
sequence design process and 4957 initiated in the real-time command process.
In the past week, 87 real time commands were transmitted: 79 were initiated
in the sequence design process and 8 initiated in the real time command
process.  In addition, 5911 mini-sequence commands have been transmitted
since March 1991; 3753 were pre-planned and 2158 were not.  In the past week,
234 mini-sequence commands were transmitted.  Major command activities this
week included commands to reconfigure the telemetry rate, update system fault
protection parameters, turn off the PLS supplemental heater, pulse the DDA
motors, and checkout the star scanner.

2.  The Dual Drive Actuator (DDA) pulse mini-sequence No. 4 covers spacecraft
activities from October 12 to October 16.  The warming turn to a 45-degree
off-sun attitude occurred on October 12.  The spacecraft remained at the
warming attitude for approximately 48 hours.  The DDA 10-pulse hammer test
occurred after approximately 46 hours at the warming attitude.  The sun
acquisition back to approximately a 5 degree off-sun attitude occurred on
October 14.  Sun Gate data was collected on October 15.  The star scanner
checkout along with the collection of wobble data is scheduled for October 16.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | If God had wanted us to
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | have elections, he would of
|_____|/  |_|/       |_____|/                     | given us candidates.

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

Date: 15 Oct 92 19:31:27 GMT
From: Michael Rivero <[e-mail]>
Subject: HRMS/SETI Answers
Newsgroups: sci.space,sci.astro

In article <[e-mail]>, [e-mail] (Nick Haines) writes:
|> 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?

  There's aother aspect. Already we are seeing mass communication moving from
carrier wave systems to cable based delivery. In light of studies which
suggest links between long term exposure to radio waves and certain
health problems in people living next to high powered transmitters,
we may see a trend of actual reduction of total planetary radio wave
output from Earth.

  That means that we might be searching for civilizations which are operating
in the narrow time perod between discovery of the radio spectrum and
the move to discreet cable communications, when their radio "noise" would
vanish from the heavens.


<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
|  Michael Rivero [e-mail]  "Middle-aged Mutant Ninja Animator" |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|  "The great masses of people. . .will more easily fall                 |
|  victims to a big lie than to a small one."                            |
|                                          --Adolf Hitler                |
|                                                                        |
|   "All men are potential rapists, and that's _all_ they are!"          |
|                                 -- Susan Brownmiller                   |
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

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

Date: 15 Oct 92 19:33:32 GMT
From: FRANK NEY <tnc!m0102>
Subject: Math progs with arbitrary precicion, for UNIX...
Newsgroups: sci.space

Where can I get a DOS or OS/2 version of Mathematica?  Keep in mind
that I do not have FTP.
--
The Next Challenge - Public Access Unix in Northern Va. - Washington D.C.
703-803-0391 To log in for trial and account info.

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

Date: 15 Oct 92 22:20:51 GMT
From: Henry Spencer <[e-mail]>
Subject: Query Re: pluto direct/ o
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>Couldn't you use a chemical first stage, then deploy a solar sail to add on
>some speed...

Getting useful acceleration from a sail, even in the inner solar system,
requires dedicating a substantial fraction of the total spacecraft mass
to the sail, and accepting a lot of hassles with deployment and control.
Light pressure is not strong enough for a little add-on sail to be a
practical propulsion system.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: Thu, 15 Oct 1992 15:52:46 -0600
From: [e-mail]
Subject: sub Juan Carlos Vazquez

SUB  Juan Carlos Vazquez

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

Date: 15 Oct 92 23:35:19 GMT
From: John Roberts <[e-mail]>
Subject: Thickness of a reflector
Newsgroups: sci.space

-From: [e-mail] (Bill Higgins-- Beam Jockey)
-Subject: Too thin for light pressure? (was Re: Diesen sphere...)
-Message-ID: <[e-mail]>
-Date: 14 Oct 92 07:38:09 GMT

-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).

.............

-From: [e-mail] (Paul Dietz)
-Message-ID: <[e-mail]>
-Date: 14 Oct 92 10:52:30 GMT

-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.

.............

-From: [e-mail] (Bill Higgins-- Beam Jockey)
-Message-ID: <[e-mail]>
-Date: 14 Oct 92 11:07:59 GMT

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

.............

And Steve Willner told me a few months ago that the reflective coating of the
HST mirror is ~.001 wavelength (I would interpret that as ~0.5 nm), which
seemed a little thin to me. Quite a range of numbers here. So - how to find
a reasonable number? The Encyclopaedia Britannica and the American
encyclopedias here use technical terms such as "thin", which are not very
useful. I finally found it in the Great Soviet Encyclopedia, of which our
library has a 1975 edition, thoughtfully translated into English, and
(very usefully) provided with an index, because the entries are in Russian
alphabetical order.

>From Volume 9, page 358: "To produce a mirror with maximum reflectance,
the thickness of the aluminum coating should be at least 0.12 um." (120 nm).
I can believe that a 50 nm coating would still be pretty reflective. Perhaps
someone who's studied crystallography or who has the atomic weight and bulk
density of aluminum handy can calculate how many atoms thick that is.

This brings back the question I had originally asked Steve Willner:
how can you grind the mirror blank for the primary mirror for HST, coat it
with something nearly 1/4 wave thick, and still have it come out figured
to within 1/80 wave (or whatever the spec was) of what you want? Is the
vapor deposition process so precisely controllable and uniform in its
effects that it does not change the shape of the surface, or changes it
in a precisely predictable manner?

John Roberts
[e-mail]

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

Date: 15 Oct 92 20:23:24 GMT
From: Tom Knight <[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.)

3 microns is more than sufficient to be totally opaque for a metal.
Silicon is barely transparent in the far red in a thickness of 2 microns.

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

Date: 16 Oct 92 08:28:00 GMT
From: Ron Baalke <[e-mail]>
Subject: Ulysses Update - 10/15/92
Newsgroups: sci.space,sci.astro,alt.sci.planetary

Forwarded from:
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE [phone]

                     ULYSSES MISSION STATUS
                        October 15, 1992

     All spacecraft and science operations are continuing
normally.  Routine Earth-pointing maneuvers were last conducted
on Oct. 10 and Oct. 13.  The next set of maneuvers will be
performed on Oct. 17 and Oct. 20.

     A reduction in the number of ranging passes continued during
this reporting period to improve the spacecraft signal at its
great distance from Earth.  Today Ulysses is nearly 11 degrees
south of the ecliptic plane, looping back toward the sun, where
it will begin its primary mission of studying the sun's poles in
June 1994.

     The spacecraft is about 890 million kilometers (554 million
miles) from Earth, traveling at a heliocentric velocity of about
32,000 kilometers per hour (20,000 miles per hour).

                             #####
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | If God had wanted us to
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | have elections, he would of
|_____|/  |_|/       |_____|/                     | given us candidates.

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

Date: Thu, 15 Oct 92 18:37:39 EDT
From: Tom <[e-mail]>
Subject: Uploaders' fate

>>When you say 'personality', do you mean that it's behavior, in all possible
>>circumstances will be the same as mine, or do you mean that the experience
>>of being 'it' is identical to being 'me'?

>As any good physicalist philosopher will tell you, there is no way of
>confirming the second apart from by the first (well, apart from brain analysis
>I guess, but we have already asumed that). The 'experience of being' is known

But, any good (or even bad :-) concious being will tell you there is
a difference.  Sure, you can't tell the difference in me, nor I in you,
but if you can't tell the difference in yourself, you aren't concious.

That's why the question, since your question, and the whole of the uploading
fate thread seem to imply the objectification of the subject.  So, if you
are going to objectify the subject, you sure do need to determine
the difference.  If you can't, how will we know if uploading is actually
successful?

>in philosophical jargon as qualia, and most good physicalists (including
>functionalists, who are the guys who believe in uploading most strongly) are
>of the opinion that qualia are just a way of saying 'innate perception', like
>a sense that is a part of your brain.

'Qualia' is also a way of saying 'me'.  If you can't tell the difference,
then uploading degenerates into a way of making highly complex robots,
not replicas of people, which, I think, takes away most of it's value.

>   When you start talking about the connection between two 'I's, then you
>are on much less philosophically complex territory. It is testable, we can
>eventually construct a duplicate, and see if this 'connection' effect occurs.

What 'connection effect'?  It's a subjective experience.  Can you show that
my colorblindness is a reality, rather than just something I make up as
a party game?

>I think not. As I side note, a creature with a truly identical mind really has
>to have received pretty much identical senosry impressions.

'Indentical mind' is pretty vague.  The only identical thing in the world
is the thing itself, so of course it would have recieved the same
sense impressions.  If you mean by identical 'unable to tell the difference
between the two' then you mean that the difference in sense impressions
is undetectable, from the impressions they left on the mind.  Whatever
the ratio between sense experience and changes in the mind is, I'm pretty
sure that 'low error' and 'identical', in term of juding other beings
experiences, from the objective evidence left over in the structure of
their brains, is vastly different.

This is pretty vague territory, isn't it?  Am I going to see a lot
of this on this list?

-Tommy Mac
------------------------------===========================================
Tom McWilliams               | Those who beleive        ' are the  ".   |
[e-mail]       | in the      ,  .        .  ones  .*'  .  |
[phone] -or- 353-2986 | Balance   '. '  . .        that , don't  |
a scrub Astronomy undergrad  |   of            ,        +         get   |
at Michigan State University | Nature                  '.  , .' eaten   |
------------------------------===========================================

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


Path: crabapple.srv.cs.cmu.edu!cantaloupe.srv.cs.cmu.edu!rochester!galileo.cc.rochester.edu!ub!dsinc!cs.widener.edu!eff!world!ksr!jfw
From: "John F. Woods" <[e-mail]>
Newsgroups: sci.astro,sci.space
Subject: Re: Diesen sphere or Strungen Sphere
Message-Id: <[e-mail]>
Date: 15 Oct 92 16:32:23 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]>
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[e-mail] (Josh 'K' Hopkins) writes:
>[e-mail] (Steve Linton) writes:
>>> 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.
>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.

If the goal is just capturing solar energy, as Dyson postulated, most of that
hydrogen can be used far enough out in the solar system where it *is* rock
(to catch the "leaks" around the plates closer in where real "rock" is needed).
I guess you'd need a thin plate around a chunk of frozen hydrogen to prevent
sublimation, but that's much less material.  And as someone else pointed out,
by the time a civilization is ready to try this stunt, a simple trick like
bulk transmutation is hardly a stumbling block...

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

End of Space Digest Volume 15 : Issue 319
------------------------------