Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_0/V10_056.TXT

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Date: Sun, 17 Sep 89 21:16:14 -0400 (EDT)
Subject: SPACE Digest V10 #56

SPACE Digest                                      Volume 10 : Issue 56

Today's Topics:
         Re: Economies of Scale in Launchers
               Re: Face on Mars
     Re: Galileo Jovian atmospheric probe -- is it sterilized???
             Re: Laser propulsion
             ATTN NASA Personnel
               News of the Week, Sep 7
             Re: Laser propulsion
         Re: Economies of Scale in Launchers
Re: Progress M-1 (new type of cargo craft) launched to USSR's Mir station
            Re: Printing on a laserwriter
----------------------------------------------------------------------

Date: 7 Sep 89 19:12:41 GMT
From: skipper![e-mail]  (Mary Shafer)
Subject: Re: Economies of Scale in Launchers


>In article <[e-mail]> [e-mail] (Bob Pendleton) writes:
>> Are we confusing high thrust with efficiency?
>
>Could be. I don't claim to be an expert...
>As I remember it, I don't have the articles with me, The effective
>back pressure is lower for a high molecular weight exhaust. I could
>have this wrong. But, "Aerospace America" is the journal of the
>American Insitute for Aeronautics and Astronautics and they did say
>that high molecular weight exhaust is preffered in the lower
>atmosphere.

No, "Aerospace America" is _not_ the journal of the AIAA.  It's not
only unrefereed but until recently, it was edited by someone who
thought that it was more important that articles read well than be
accurate.  However, I believe that a new editor has recently been
hired, so the technical content may soon be reliable again.

I say this as an AIAA Associate Fellow, who has been receiving
"Aerospace America" (or its predecessor, "Aeronautics & Astronautics")
for 12+ years.  However, the AIAA Bulletin in the back, with the calls
for papers and announcements of AIAA conferences and short courses, is
quite reliable.

The _real_ journal you're interested in is the "Journal of Spacecraft
and Rockets."  Real technical papers, written, reviewed, and edited
by technical people working in the field.

There also a "Journal of Propulsion and Power" but I don't know whether
this includes non-airbreathing engines.  Again, a _real_ journal.

Better than AA, but not totally technical is "Aerospace Engineering"
from SAE.  SAE probably also has specialist journals, but I don't
know about this.

--
--
Mary Shafer   [e-mail]  arpa!elxsi.dfrf.nasa.gov!shafer
         NASA Ames-Dryden Flight Research Facility, Edwards, CA
                    Of course I don't speak for NASA

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

Date: 7 Sep 89 20:28:33 GMT
From: [e-mail]  (Kevin William Ryan)
Subject: Re: Face on Mars


   As someone who does a _lot_ of image processing on a variety of images, I
have noted that you must be careful how you are enhancing your images.
Different enhancement techniques, in various orders, will enhance vastly
different parts of an image.  You can bring up aspects of an image that were
difficult to see or masked by other information - you can just as easily
suppress information that might lead to another conclusion.  You can quite
simply emphasize features of a given size within a specific grey scale, while
throwing away equally important information elsewhere.  You have to be real
careful about what you do, and should maintain a history of your manipulation
so that others can confirm and/or criticize your work.
   I have the 100x100 images that were posted of the face - I will be decoding
and examining them as soon as I have some spare time...  If anyone wants I
can give my opinion of them at that point...

                                            Kevin Ryan
                                            Asst. Dir. Imaging Technology
                                            Biological Sciences
                                            Carnegie Mellon Univ.

        [e-mail]

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

Date: 7 Sep 89 05:36:48 GMT
From: ibmpa![e-mail]  (nick szabo)
Subject: Re: Galileo Jovian atmospheric probe -- is it sterilized???

>The following is from the Christic Institute in Washington, D.C.
>...
>A number of experts believe that despite the harsh
>environment of outer space, a large colony of earth
>microorganisms will survive the journey to Jupiter in the
>interior of the spacecraft.

Who are the "experts" of whom you speak?  Be specific.  Galileo will pass
through temperature and radiation extremes from ranging from Venus orbit
to Jupiter.  It will be in vacuum.  No nutrients.

>The probe's
>unsterilized parachute will probably carry billions of live
>microbes.

Again, please cite evidence for this claim.

>Although conditions on Jupiter are very different from
>earth, the planet's atmosphere includes clouds of liquid water at
>temperatures at which earth microbes could survive and grow.

What about necessary proteins, minerals, vitamins, etc.?   What about
the updrafts/downdrafts and temperature extremes?   Have any experiments
performed or was this just a research paper?

>Even if the microbes could not survive on their own, the Sagan
>paper suggests they could find a supportive environment inside
>native organisms on the planet.

This is, for all practical purposes, impossible (see below).

>The Christic Institute supports the exploration of the outer
>planets, but urges NASA to postpone the Galileo mission until the
>spacecraft is sterilized and its plutonium generators are
>replaced by a safer alternative energy source.

Yes indeed, the Christic Institute has just been so active promoting
space exploration.  Where were you when the Saturn rockets were scrapped?
Where were you when Galileo, Magellan, Mars Observer, Ulysses, Hubble,
etc. were delayed?  What are you doing now for CRAF, Cassini, and the
Lunar Polar Orbiter?

The plutonium generators cannot be "replaced".  No technology exists to
field an equivalent generator with equivalent mass, space and thermodynamic
properties.  Essentially Mariner Mark II (Galileo, CRAF, and Cassinni) would
have to be scrapped, and a new spacecraft designed, with technology that is
currently speculative.

In article <[e-mail]> [e-mail].e
du (Wayne Hayes) writes:

>irresponsible mistake, to launch the atmospheric probe.  In the remote
>possibility that Jupiter's atmosphere harbors indigenous life, we may
>pollute the atmosphere with Earth's life and never know for sure whether
>the life we later discover is in fact indigenous.

It will be very easy to discriminate life native to Jupiter or other
planets from Earth life, just as it is easy to distinguish bats from
birds, or prokaryotes from eukaryotes.  Earth life consists of only
a minscule fraction of possible DNA combinations (something like
10^14/4^10,000=1/10^5,986).  Even if we go wild with the Drake equation,
and assume DNA is the only possible structure for life, there will be
no repititions, or even anything close, to Earth life anywhere else in
our galaxy.

In fact, all Earth life will be like brothers and sisters in structure,
compared to any independently evolved ET life.  This relates
to another issue.  Diseases will not spread between Earth and
ET life, for the same reason that you can't give influenza to a tree.
Diseases rely on identicalities (not just similarities) in their hosts to
propagate.  Of course, toxins of simple chemistry produced by Earth forms
may well harm extraterrestrial forms, and vice versa.

There are speculative scenarios where life on Jupiter and Earth did
*not* independently evolve.  For example, perhaps Jupiter and Earth
forms are both decended from prokaryotes that evolved in comets.
In which case, there will be some similarities, but we can still deduce
that species found on both Earth and Jupiter came from Earth, and species
found only on Jupiter are native to Jupiter.  Disease risk will come
only from diseases that infest both prokaryotes and eukaryotes--ie none.

All Earth organisms inhabit a specific niche.  The chance
that a random bacteria can use a Jupiter niche, radically different than
any on Earth, better than a Jupiter native, is slim to nil.

"An investment does not owe you anything."
                        Max Gunther

--
--------------------------------------------
Nick Szabo
uunet!ibmsupt!szabonj
These opinions are not related to Big Blue's

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

Date: 7 Sep 89 16:18:14 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Laser propulsion

In article <[e-mail]> [e-mail] (Walt Leipold) writes:
>... As the rock leaves the center of the beam,
>it contacts the opposite 'wall' of the beam, and the thrust generated
>by the explosion of that part of the rock forces the rock back toward
>the beam center.

A beam powerful enough to do that is powerful enough to be a weapon in
its own right, with far higher rate of fire than laser-steered rocks.
--
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry [e-mail]

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

Date: 7 Sep 89 15:16:58 GMT
From: hp-pcd!hpcvlx![e-mail]  (Greg Goebel)
Subject: ATTN NASA Personnel

I try to keep up with space activities; and I notice that NASA gets
raked over the coals on a regular basis (not only here on the net but
in publications like SCIENCE and others).

As a somewhat distant observer, it is difficult for me to take such
criticisms at face value; I am in no position to make a serious evaluation
of them.  However, as a person with a journalistic bent, I'm always
interested in hearing the other side of the story.

So ... out of curiosity ... I know there are a lot of NASA people on the
Net -- what do YOU people think of NASA's situation?  Or, to be more
specific:

   * Are the criticisms of NASA justified?
   * What are the prospects of NASA's future activities?
   * If NASA is in need of reorganization, what proposals would make sense?
   * How does space commercialization fit into the picture?

I realize that speaking frankly in a large organization can be very dangerous
(I always think twice or three times before saying anything that even could
be misinterpreted as sounding bad about HP!) so I suggest email would make
more sense than posting responses.  All such responses would be in strictest
confidence; I might consider a posting summarizing the responses I got, but
I would make no quotes, name no names, and make no references to specifics
that might identify a particular individual unless specifically authorized to
do so.

    +---------------------------------------------------------------------+
    | Greg Goebel                                                         |
    | Hewlett-Packard CWO / 1000 NE Circle Boulevard / Corvallis OR 97330 |
    | [phone]                                                      |
    | INTERNET: cwo_online@hp-pcd                                         |
    | HP DESK:  CWO ONLINE / HP3900 / 20                                  |
    +---------------------------------------------------------------------+

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

Date: 8 Sep 89 14:51:21 GMT
From: frooz!cfa250![e-mail]  (Jonathan McDowell)
Subject: News of the Week, Sep 7

Jonathan's Space Report

Sep 7, 1989 (no.24)
Happy Plutonic Perihelion!
---------------------------------------------------------------------

Soyuz TM-8 was launched from Baykonur on Sep 5 and docked with the Mir
orbital station on Sep 7.  The crew are Aleksandr Viktorenko (Kdr) and
Aleksandr Serebrov (BI, or flight engineer).

The final Titan 34D was launched on Sep 4 from Cape Canaveral.  AvLeak
prelaunch reports suggested the payload was a pair of DoD comsats (DSCS
II F-16 and DSCS III F-4) with an IUS upper stage, but I have not
managed to confirm this.

Kosmos-2037, launched Aug 28 by Tsiklon from Plesetsk, is a geodetic
satellite.

NASDA's Himawari-4/GMS-4 weather satellite was successfully
launched from Tanegashima, Japan by H-I vehicle on Sep 5.

(c) 1989 Jonathan McDowell

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

Date: 9 Sep 89 00:45:22 GMT
From: vsi1!daver!lynx![e-mail]  (Neal Woodall)
Subject: Re: Laser propulsion

In article <[e-mail]> [e-mail] (Walt Leipold) writes:

>.......It involves using a big
>rock as a kinetic kill 'vehicle', launched via railgun or some other
>high-velocity technique.  To guide the rock, you aim a toroidal
>high-energy laser at it, then simply swing the laser to point at the
>target you want to destroy.  As the rock leaves the center of the beam,
>it contacts the opposite 'wall' of the beam, and the thrust generated
>by the explosion of that part of the rock forces the rock back toward
>the beam center.

Interesting idea, but don't you think that a laser (or any directed
energy device) that powerful would be a formidable weapon itself?









Neal

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

Date: 9 Sep 89 22:40:50 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Economies of Scale in Launchers

In article <[e-mail]> [e-mail] (Bob Pendleton) writes:
>Can anyone tell me if there is a relationship between mass flow rate
>and optimal nozzle skirt length? A relationship that is independent of
>back pressure.

Mmm...  mass flow rate is proportional to throat area.  For a given flow
rate, assuming negligible back pressure, maximum thrust comes with the
longest possible nozzle, for maximum expansion.  But nozzles weigh something,
so there is a length tradeoff.  The square-cube law says the nozzle gets
heavier faster than the throat gets bigger, so optimizing for thrust/weight
ratio will favor longer nozzles for smaller engines.  There are lots of
hidden assumptions in this, though.  I'm not aware of any specific formal
relationship.

>So, Henry, when are you going to post the text of your talk at the BIS
>bash in Boston?

Shortly after I get back from my first visit to the Moon. :-)  That talk
was long -- much longer than I'd thought it would be -- and typing it up
would be quite a job.
--
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry [e-mail]

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

Date: 7 Sep 89 16:18:51 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Progress M-1 (new type of cargo craft) launched to USSR's Mir station

In article <[e-mail]> [e-mail] (Matthew Francey) writes:
>  An un-manned vehicle will dock with an un-manned space station?  Is this
>possible? (Well, of course it is possible... can anyone do it?)

Yes.  The Soviets do it all the time.  The US can't do it yet.
--
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry [e-mail]

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

Date: 7 Sep 89 20:27:38 GMT
From: lorelei![e-mail]  (Laura Lemay)
Subject: Re: Printing on a laserwriter


The original article was NOT SUPPOSED to be cross-posted to this group.
It was A MISTAKE.  I didn't check the newsgroups in the header
I was working on.

I heartily apologize for any confusion and/or anger this may have caused
you.  Tho you should have been able to figure it out.  We're all smart
people here.

So why don't you just hit the 'n' key when you come across a cross-posted
followup, or even better, put it in your kill file (ooh, what a concept.),
instead of sending me abusive mail every time.  OK?


thank you for your attention --






-Laura Lemay            [e-mail]
Redhead.  Drummer.  Geek.

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

End of SPACE Digest V10 #56
*******************