Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_3/V11_348.TXT

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Subject: SPACE Digest V11 #348

SPACE Digest                                     Volume 11 : Issue 348

Today's Topics:
         Update to "Listening to the Stars".
     Re: PegBlimp (was Re: Pegasus launch from Valkyrie (or ...)
        Re: (How to get rid of) space garbage
                 Apollo 11-17
        Re: (How to get rid of) space garbage
   Re: Niven's inertialess drive (was Re: Dyson spheres, heat flow)
Re: Giant crawler transporter to pass 1000 miles on STS-35 rollout (Forwarded)
             Re: * SpaceNews  30-Apr-90 *
          Phhotos from Space (was: Hubble Telescope)
        Re: (How to get rid of) space garbage
----------------------------------------------------------------------

Date: 3 May 90 03:50:03 GMT
From: usc!samsung!munnari.oz.au!gwydir!gara![e-mail]  (Philip Nettleton)
Subject: Update to "Listening to the Stars".

0. The Debate.

From the debate I appear to have started concerning methods of long distance
communications, it is evident that a few people have got slightly off the track.
Let us tackle the most frequently mentioned types of telecommunication
separately and see what we get.

The first question is what uses do we put telecommunications to in our (modern)
society (not forgetting that we may well be rank amateurs in this branch of
technology).

(a)     Communications.
(b)    Navigational aids.

1. Communications.

One hundred years ago we had a number of methods of communications but how
many are still used today? Not many and none to speak of that produced
electromagnetic (EM) transmissions of any note.

Why is this? Well, basically, because we discovered better and more cost
effective ways of sending information. We don't use the telegraph any more
because it is obsolete. The principles are still there in telephone but
even that is changing with the use of fibre optics and telephones themselves
have greatly changed over time.

Satellite communications are used extensively in this era, but in a hundred
years time? If a method could be developed whereby we could transmit signals
unimpeded through the body of the Earth, satellites would no longer be cost
effective and such a method would be unlikely to use EM transmissions.

What about communicating to other worlds? Inside the solar system we could
still use EM transmissions to send messages in a reasonable time (by today's
standards), a few minutes or hours at most. In a hundred years time we will
not be satisfied with such excessive delays, businesses and governments
will demand faster responses and technology will have to supply it. Beyond
our solar system the issue is even more critical. No one is going to wait
around a few years to receive news from a remote settlement.

So what would an advanced technological species need to serve its basic
interstellar communications needs? Well, a faster than light communications
system that could traverse through normal matter without noticeable
distortion. A tall order you say, but what if we don't develop such a
method? I guess we'd better learn to make do with this little planet of
ours that we are so rapidly destroying.

The point I was making before was that we cannot even guess at what would
be required for such a method of communication but technology may well
supply it in the near future, and then what would we need EM transmissions
for?

2. Navigational Aids.

Radar and navigational satellite systems may well be around for quite some
time because both of them negate principles outlined above. In both
these cases we need the Earth to act as an obstacle reflecting or blocking
our EM transmissions. However, for interstellar space flight, it could be
that entirely new methods are developed which could be applied back on Earth.
These, again, would be unlikely to use EM transmissioned because they are so
slow.

3. Electronical and Electronic Emissions.

One of the most interesting aspects of the debate was over unintentional
EM transmissions from electrical and electronic devices. Most devices
produce EM transmissions when in operation, even though they have shielding
to minimise the volume of EM leakage. The problem with detecting leakage
of EM transmissions from another world is that it would show up as so much
static, indistinguishable from natural EM sources.

4. In Summation.

So I reinterate, there would perhaps be a window of 200 (terran) years in
the history of a sentient species where they MAY knowingly or unwittingly
transmit EM signals between themselves, maybe much shorter if they don't
survive the invention of mass destructive weaponry and the ravages of
ecological irresponsibility. (They could even simply be smarter than us,
which I realise to some would be totally unthinkable).


                    Philip Nettleton,
                    Tutor in Computer Science,
                    University of New England,
                    Armidale,
                    New South Wales,
                    Australia.

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

Date: 2 May 90 06:29:07 GMT
From: hplabsb![e-mail]  (David Smith)
Subject: Re: PegBlimp (was Re: Pegasus launch from Valkyrie (or ...)

In article <[e-mail]> [e-mail] (Walt Leipold) writes:
>"As long as you've lit one candle,                         Walt Leipold
>you're allowed to curse the darkness."       ([e-mail])

Curse the candle, let's have the night sky!
--
    David R. Smith, HP Labs
    [e-mail]
    [phone]

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

Date: 2 May 90 16:27:40 GMT
From: swrinde!zaphod.mps.ohio-state.edu!sdd.hp.com!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: (How to get rid of) space garbage

In article <[e-mail]> [e-mail] (Jonathan Leech) writes:
>...ways to get rid of orbital debris.  First off the wall
>suggestion: use high-powered lasers to accelerate decay from the
>Poynting-Robinson effect...

No need to invoke something as slow as the P-R effect.  Use the lasers
more directly:  vaporize small fragments, de-orbit larger ones by laser
rocketry (blowing bursts of gas off their leading faces).  If I recall
correctly, Jordin Kare said that even the first-phase proof-of-principle
laser for a laser-launcher system could do a dandy job on this.
--
If OSI is the answer, what is |     Henry Spencer at U of Toronto Zoology
the question?? -Rolf Nordhagen| uunet!attcan!utzoo!henry [e-mail]

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

Date: 3 May 90 02:05:14 GMT
From: dino.qci.bioch.bcm.tmc.edu![e-mail]  (Timothy B. Reynolds)
Subject: Apollo 11-17

Ok here's a trip back in history.
In the late 60's or early 70's I remember watching TV when the
astronauts were walking on the moon, one of the major networks
was doing the "moon-walk" simulations with puppets of the astronauts.
The looked very real ! Anyway I have spent 15 years calling the networks
trying to find out where these puppets came from or who made them.
On the broadcast they even interviewed the man that was operating them !
No one I have talked with remembers this (at the nets) if I remember
correctly it was WALTER CRONKITE that did this, this means means CBS.
If anyone has any info on this or remembers it please e-mail me
with the details. I WONT GIVE UP...

                                                 Thanx...T
==============================================================================
     Timothy B. Reynolds               |             VAX Systems Manager
Howard Hughes Medical Institute        |         Structural Biology Laboratory
  Baylor College of Medicine           |               Houston, Texas
==============================================================================
Disclaimer: My opinions are my own, not HHMI's or Baylor College of Medicine
==============================================================================

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

Date: 2 May 90 17:02:19 GMT
From: sdd.hp.com!zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!aristotle![e-mail]  (Peter Scott)
Subject: Re: (How to get rid of) space garbage

In article <[e-mail]>, [e-mail] (Jonathan
Leech) writes:
>
>     In light of the current 'life of HST' discussion, maybe we could
> talk about ways to get rid of orbital debris.  First off the wall
> suggestion: use high-powered lasers to accelerate decay from the
> Poynting-Robinson effect.  If this thread takes off, I'll run some
> numbers on this suggestion.

Since I saw a similar suggestion in the space-tech group, I've been
impressed with this idea.  The suggestion was to use a mirror to
reflect sunlight onto trash to deorbit it gradually.  I think this is
an even neater suggestion, since it doesn't require any onboard power
and could be launched right now.  I don't understand why this isn't
being pursued vigorously, since it would have the greatest effect on
the small trash and very little on larger items such as satellites.
Of course, one would hope that it wasn't in the wrong position when
Hubble came around one orbit, or whoops...

Maybe you could run some numbers for the mirror; what diameter Mylar
film to deorbit 50% of LEO junk < .5cm within 6 months, say?

This is news.  This is your       |    Peter Scott, NASA/JPL/Caltech
brain on news.  Any questions?    |    ([e-mail])

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

Date: 2 May 90 23:49:21 GMT
From: sdd.hp.com!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!mephisto!prism![e-mail]  (Shannon Bell)
Subject: Re: Niven's inertialess drive (was Re: Dyson spheres, heat flow)

In article <[e-mail]> [e-mail] (Steven P Coltrin) writes:

:In article <[e-mail]> [e-mail] (Clive D.W. Feather) writes:
:>But in "Flatlander" an Outsider ship accelerates Beowulf and Elephant to 0.9c
:>in a matter of minutes. This can't be a simple reaction drive; it has to act
:>on the occupants as well as the ship, or they'd be squashed.
:>
:The Outsiders likely just have unghodly gravity generators and are able to
:compensate.  I'm not nearly sure, but I think one of the Louis Wu stories
:mentions grav. generators needed to compensate for thruster acceleration.

Or maybe they used the anticoncussion field from _The_Soft_Weapon_. While
Niven didn't give any particulars about the operation of the field, I don't
thing gravity generators could do that (basically an anti-motion field)
and still not generate a healthy change in perceived weight. Perhaps
something like an inductor, but acting on kinetic energy in a volume,
rather than electricity in the wire?

Shannon Bell                   Internet: [e-mail]
uucp:      ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!ccastbs
PO Box 36266   Georgia Institute of Technology, Atlanta Georgia, 30332
Any opinions herein are probably not held by Ga. Tech, even if I say they are.

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

Date: 2 May 90 16:22:13 GMT
From: convex![e-mail]  (Edward V. Wright)
Subject: Re: Giant crawler transporter to pass 1000 miles on STS-35 rollout (Forwarded)

[e-mail] (Henry Spencer) writes:

>power.  They burn Diesel oil; mileage is something like 30 ft per gallon.

Don't you mean footage? -:)

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

Date: 2 May 90 21:56:15 GMT
From: uokmax![e-mail]  (Michael Dean Thompson)
Subject: Re: * SpaceNews  30-Apr-90 *

In article <[e-mail]> [e-mail] (John Magliacane) writes:
>
>
>* STS-31 NEWS *
>===============
>Mike (WD8KPZ) of Phoenix, Arizona reported hearing space shuttle astronaut
>communications on a frequency of 279.000 MHz AM during their EVA during the
>deployment of the Hubble Space Telescope.
>
>Mike used an Icom R-7000 receiver and a quarter-wave ground plane antenna at
>an altitude of 15 feet to receive the astronauts.

When I watched the deployment of the Hubble,  I never remember Bruce or Kathy
being let out of the airlock.  So when was this EVA?  (I'm sure Bruce would
like to know :-) )


--
        [e-mail]
    "I don't know...I can imagine quite a bit..."
                        H. Solo

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

Date: 2 May 90 14:55:08 GMT
From: philmtl!philabs!ttidca![e-mail]  (Dick Jackson)
Subject: Phhotos from Space (was: Hubble Telescope)

In article <[e-mail]> [e-mail] (Russ Tillman) writes:
>something they understand.  I remember back in the 70's, that while enroute to
>Jupiter, Pioneer took a picture of both the earth and the moon in the same
>frame.  A picture like that get's people thinking!

Is there not a plan to have Voyager turn around to get a family snap of
the solar system? Has this been approved?

Dick Jackson

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

Date: 3 May 90 05:03:45 GMT
From: deimos.cis.ksu.edu!maverick.ksu.ksu.edu!uafhp![e-mail]  (Brian L. McCormick)
Subject: Re: (How to get rid of) space garbage

In article <[e-mail]>, [e-mail] (Christopher Neufeld) writes:
[stuff deleted]
> ... My proposal was to have a 300km diameter mirror out
> around 80000km from the Earth, balanced off the solar radiation pressure
> and the Earth's gravitational pull. Essentially, it is a solar sail which
> can't quite get away from the Earth's pull when it's 80000km out. The
> existing solar sail technology seems to indicate it should work.
[more stuff chopped]
> Because of the way it is positioned, it has a 100% duty cycle. It does not
> orbit the Earth, but floats ahead of it in orbit around the Sun.
[remainder zapped]

I am not particularly inclined towards the mathematics of this sort of
calculation, but it seems to me that this proposal ignores the gravitational
effect of the moon on an object "floating" in the vicinity of the Earth.
I have heard that the moon has enough of an impact to shorten the orbital
life of satellites considerably and it seems as though this effect would
be much more significant for an object that is not actually orbiting the
Earth.  Any thoughts on whether or not such an orbit is actually possible?

--------------------------------------------------------------------
(|||)  Brian McCormick     a.k.a.     [e-mail]  (|||)
 |||   - I deny being in any way affiliated with engineering -  |||
(|||)     Any disclaimer you can think of probably applies.    (|||)
--------------------------------------------------------------------

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End of SPACE Digest V11 #348
*******************