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Subject: SPACE Digest V11 #308

SPACE Digest                                     Volume 11 : Issue 308

Today's Topics:
          Re: Radar (was Re: Drake Equation
              Re: Dyson spheres?
NASA to brief media on Hubble Space Telescope instrument test (Forwarded)
           Re: Questions about the Voyagers
          Launch date set for Consort 3 (Forwarded)
       Re: Drake Equation (was Re: Interstellar travel)
              Re: Decompression and 2001
                Re: Our galaxy
----------------------------------------------------------------------

Date: 24 Apr 90 02:21:02 GMT
From: zephyr.ens.tek.com!wrgate!mrloog![e-mail]  (Dan Tilque)
Subject: Re: Radar (was Re: Drake Equation

[e-mail] (John Sahr) writes:
>[e-mail] (Dan Tilque) writes:
>[]
>>Now the largest military radars (as I said in an earlier post) are
>>large phased array systems which watch for ICBMs.  The U.S. has five of
>>them (or did that last I heard).  Three of these, located in Alaska,
>>Greenland and England, look for missiles launched from the Soviet
>>Union.  The other two are located on the U.S. east and west coasts and
>>look for submarine launches missiles.  These last two use over the
>>horizon radar (using a troposcatter effect, I think) so much or most of
>>their emissions probably do not escape to space.
>
>OTH radars use ionospheric refraction to see "over the horizon."

That's right.  I was confusing radar with an over the horizon microwave
comm system.


>>In order to detect ICBMs, these radars would have to have ranges of
>>about 2 or 3 times that of regular radars.  That means that (assuming
>>similar receiver sensitivity) they would use 16 to 81 times the power
>>of ordinary radar (which typically run about 2-5 MW).
>
>Not necessarily true.  For an OTH radar, the signal return is
>currently limited by clutter, notably ionospheric irregularities.
>Thus, increasing the transmitter power just increases the clutter.

Henry Spencer has already pointed out that the ICBM detection radars are
line of sight called BMEWS (for Ballistic Missile Early Warning System).
I couldn't remember the acronym when I made my post (thanks, Henry).
It's these guys which are the large phased array systems.  There are three
of them which cover a huge arc of territory from the Gulf of Alaska,
across the North American Arctic and over to Europe.  They have to be
powerful to do that.

The OTH systems were called "Pave Paws" the last I heard.  That's a code
word, they may have assigned an acronym to them by now.  These look for
submarine launched missiles.

>Even for the DEW-line radars, it may be pointless to increase the
>power.

The DEW line radars are probably about as powerful as other USAF airplane
detection radars, i.e. 2-5 MW.

To get this back on the topic of aliens detecting these from out there --
most of these powerful radars (BMEWS, DEW, etc and Soviet counterparts)
are primarily located in the northern hemisphere, in fact, many are well
north of 50 degrees north.  Thus aliens from stars in that section ofthe
sky are much more likely to detect us than other aliens.

>>of ordinary radar (which typically run about 2-5 MW).
>
>2-5 MW is a pretty boss transmitter, no matter what.

2-5 MW is what most long range Air Force search radars typically operate
at.  You must remember that the enemy planes are not necessarily going to
have their IFF/SIF turned on.

>Radio amateurs familiar with "meteor scatter" accompish hard target
>scatter at hundreds of kilometer ranges with a few hundred watts of
>transmitter power.

Remember, radar operates under an inverse 4th power function.

---
Dan Tilque    --    [e-mail]

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

Date: 23 Apr 90 12:54:38 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Re: Dyson spheres?

In article <[e-mail]> [e-mail] (Steve Robiner) writes:
>In article <[e-mail]> [e-mail] writes:

>>    the advancement  of some civilizations,  they  would  develop  the
>>    ability to  transform all of the matter of their solar system into
>>    a very thin  layered  hollow sphere  centered  on  their star.  In
>>    this way  they could fully utilize the total stellar energy output
>>    as well as the maximum surface area on the interior of the sphere.
>
>A civilization that advanced would surely not need a star as an energy source.
>In order to move that much mass around you would have to have a very advanced
>energy source already.  And since such a sphere would have no 'gravity' or
>other centripital forces at its poles, and no 'night' anywhere on the surface,
>the simple creation of another planet would be far more preferable.

The energy output of a sun is more than enough to reengineer a solar
system, given thousands or millions of years.

It's a common misconception that Dyson was talking about a single
solid sphere of material.  In fact, he was talking about a large
collection of objects, independently orbiting at different distances
from the star, that (collectively) englobe the star.

Also, the name "Dyson sphere" was coined by SF writers; Dyson himself
says he got the idea from Olaf Stapledon's (sp?) SF works of the early
20th century ("Last and First Men", I think).

>>    Dyson  recognized that an Earth-based observer would  see  a  very
>>    bright infared source with no visible component.
>>
>If they were that advanced, they'd surely contruct the sphere out of materials
>which fully absorbed all the energy from the star in *every* wavelength.  We
>would never see it even if they did exist.

Unless they have figured out how to violate the second law of thermodynamics
(in which case they don't need a sun), they have to dump waste heat
somewhere.  It is this waste heat Dyson was talking about.

    Paul F. Dietz
    [e-mail]

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

Date: 23 Apr 90 21:28:57 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: NASA to brief media on Hubble Space Telescope instrument test (Forwarded)

Paula Cleggett-Haleim
Headquarters, Washington, D.C.                     April 23, 1990
(Phone:  [phone])


N90-26 Editors Note
NASA TO BRIEF MEDIA ON HUBBLE SPACE TELESCOPE INSTRUMENT TEST


     Approximately 7 days after deployment of the Hubble Space
Telescope (HST), NASA engineers will be obtaining a test image of
star field NGC 3532 from the Goddard Space Flight Center (GSFC),
Greenbelt, Md.  Media can view this image from the HST newsroom,
located in the GSFC Visitors Center.

     Prior to NASA's reception of this first test image, media
will be briefed on how the telescope is focused and the image is
captured.  The exact time of the image capture cannot be
determined until after deployment and a number of maneuvers have
been successfully conducted.

     During the mission of STS-31, an update will be given on the
approximate time of the engineering test briefing at a change-of-
shift news briefing.

     The complete orbital and science verification period, which
ensures that all systems and instruments are functioning
properly, extends over an 8-month period.

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

Date: 23 Apr 90 17:34:35 GMT
From: usc!elroy.jpl.nasa.gov!jato!mars![e-mail]  (Ron Baalke)
Subject: Re: Questions about the Voyagers

In article <[e-mail]> [e-mail] (Robert Casey) writes:
>In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>>
>>I don't know what the situation is right now, but in the long run, as
>>projects like Magellan and Galileo demand increasing chunks of DSN's time,
>>much of the (fairly boring and routine) data the Voyagers are sending will
>>be lost.  It won't all be lost, as there is still some value to it
>>
>I would have thought that the Voyagers would store the data for transmission
>at scheduled times, chosen to be received at Earth when the antennas are not
>needed for the newer probes.  Use the on-board "video" tape that was used to
>store images at planet encounters for storing the cruise data?

This is what happens. However, the Voyagers are given low priority on antenna
time, and since it takes over 8 hours to receive any data from Voyager, it is
often the case the data will be transmitted back to deaf ears.  The family
portrait images sat in Voyager's tape recorders for over a month before they
were allocated DSN time.  DSN utilization will be at an all time high this
fall when Galileo playback its Venus science data and does an Earth flyby,
when Magellan will enter Venus orbit and start mapping the planet, and when
Ulysses is launched.

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 23 Apr 90 21:22:15 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: Launch date set for Consort 3 (Forwarded)

Barbara Selby
Headquarters, Washington, D.C.                    April 23, 1990
(Phone:  [phone])

Rick Mould
University of Alabama-Huntsville
(Phone:  [phone])

Walter Pennino
Space Services, Inc., Houston
(Phone:  [phone])


RELEASE:  90-58

LAUNCH DATE SET FOR CONSORT 3


      The launch of Consort 3, a commercial suborbital rocket
carrying 12 microgravity experiments, has been set for May 17 at
10:40 a.m. EDT, by the University of Alabama-Huntsville's (UAH)
Consortium for Materials Development in Space (CMDS), a NASA
Center for the Commercial Development of Space (CCDS).

      Consort 3 will be launched from the Naval Ordnance Missile
Test Station facilities at the U.S. Army's White Sands Missile
Range (WSMR), N.M., by Space Services, Inc., Houston, using its
Starfire rocket.  The rocket will carry the payload to an
altitude of 200 miles and will provide the experiments
with 7 to 8 minutes of microgravity time.

      The rocket and launch services are funded by a grant from
NASA's Office of Commercial Programs, Wash., D.C.  Commercial
participants provided most of the funding for the payload.

      The Consort 3 mission will carry experiments from three
other NASA commercial development centers.  They include the
Center for Advanced Materials, Battelle Columbus Laboratories,
Columbus, Ohio; the Center for Cell Research, Penn State
University, State College; and the Center for Bioserve
Space Technologies, University of Colorado, Boulder.

      The UAH CMDS and the Center for Advanced Materials will
perform materials science experiments, while the Penn State and
Colorado centers will conduct biotechnical experiments, each
using the effects of microgravity in their investigations.

      This is the third commercial launch for the UAH CMDS and
Space Services.  Consort 1, carrying six microgravity
experiments, was successfully launched on March 29, 1989.

      Consort 2, launched Nov. 15, 1989, was terminated 30
seconds into the flight by the WSMR range flight safety
personnel.  However, the undamaged payload was recovered by
parachute.  The Consort 3 experiment package is essentially the
same payload as the aborted Consort 2 mission.

      An incident investigation board, chaired by Space Services,
Inc., determined that the Consort 2 flight anomaly was caused by
a mechanical failure in the MIDAS gyro platform that provides
attitude reference input into the S19 boost guidance system.  The
loss of the platform caused the vehicle to cone, which lead to
high structural loads and premature separation of the payload
from the booster.

      "Management and independent experts have carefully analyzed
the known and other potential failure modes," said Donald (Deke)
Slayton, President of Space Services.  "All possible corrective
actions have been taken."



                            - end -

NOTE TO EDITORS:

      While this event is not open to the general public, news
media representatives may attend.  Requests for accreditation to
attend the launch of Consort 3 should be submitted directly by
May 10, 1990, to:

      Debbie Bingham, PAO
      Building 122
      White Sands Missile Range, N.M.  88002-5057

      Phone:  [phone]

      Radio and television reporters planning live coverage
directly from the range are required to submit their transmission
frequencies to the WSMR Department of Defense Area Frequency
Coordinator (505/678-5417) for approval to transmit.  Requests
must be received no later than May 7, 1990.

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

Date: 23 Apr 90 17:41:58 GMT
From: att!cbnewsl!moss![e-mail]  (Forrest Gehrke,2C-119,7239,ATTBL)
Subject: Re: Drake Equation (was Re: Interstellar travel)

In article <[e-mail]>, [e-mail] (Steve Nuchia) writes:
> The 10 Hz beat would be interesting.  The phase relationship
> probably doesn't change very much, since most grids are phase-locked
> to a coordinated time base.

If you think a beat could be detected any distance out beyond the
earth, build yourself a low frequency receiver and listen for it
right here on Terra Firma.  You will be rewarded with more racket
than you ever dreamed possible, but no 10 hz beat.  I have read
somewhere that at any moment there are several thousand lightning
storms going on somewhere on earth.  You will think you are
hearing them all.

I know that receivers that operate below the standard broadcast
band are not plentiful, but if you ever have the chance to
listen to one you will learn that those wavelengths are a
far piece from what you hear in the FM band.  A lightning bolt
has to be within visible distance to hear it at these
short wavelengths.

As to radiation from high power transmission lines, consider for
moment how much radiation you would get from an antenna array whose
element current vectors at all points add up to virtually zero.  Why
would you expect to get any substantial far field radiation from such
an antenna?

Forrest Gehrke [e-mail]

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

Date: 23 Apr 90 19:47:24 GMT
From: convex![e-mail]  (Edward V. Wright)
Subject: Re: Decompression and 2001

[e-mail] (Blake Philip Wood) writes:

>In being exposed to a vacuum
>you certainly wouldn't want to simply open your mouth, because with no
>air in your lungs you have only about 15 sec of consciousness.  The best
>strategy may be to exhale and hold that.


In some of his science fiction stories, when there was a sudden decompression,
Jerry Pournelle had his characters scream to force as much air as possible
out of there lungs.

Dr. Pournelle was the head of Boeing's human factors research lab during
part of the Apollo program.  He should know what he's talking about and
usually tries to get things right in a story.

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

Date: 23 Apr 90 15:19:06 GMT
From: haven!aplcen!jhunix![e-mail]  (Garrett A Wollman)
Subject: Re: Our galaxy

In article <[e-mail]> [e-mail] (Will Martin) writes:
>[...] Or perhaps
>a Latinized name like we use "Terra" instead of "Earth"? [Since, actually,
>both of those words can be translated to "dirt", they really are not
>very dignified names for the home planet. I suppose every intelligent
>extraterrestrial species has a name for their home planet that means
>"dirt"... Is there *any* Earth language that has a name for the planet
>that is different from the word for "dirt" or "soil" or "ground"?]

How about Sol-3?

Of course, that's cheating.  What we need is a numbering system that's
not so geocentric; we should chose some other center (perhaps that
hypothetical point 10 kpc away?) from which to base our system...still
purely arbitrary, but it would at least free us to speak in less charged
terms about our home.


-GAWollman


--
"All societies are based on rules to protect pregnant women and children.
 . . . As racial survival is the only universal morality, no other bases
 is possible."           - Lazarus Long [RAH, _TEFL_]
---------------Hopkins doesn't *want* my opinions------------------------

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

End of SPACE Digest V11 #308
*******************