Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_2/V15NO268.TXT

Internet Message Format | 1993-07-13 | 36KB

Date: Thu,  1 Oct 92 05:14:23
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #268
To: Space Digest Readers
Precedence: bulk


Space Digest                Thu,  1 Oct 92       Volume 15 : Issue 268

Today's Topics:
                       another sad anniversary
                       Clinto and Space Funding
                        Disney's Man in Space
                        Long-term investments
                              Population
                            Porous Silicon
       PUTTING VENUS IN AN ORBIT SIMILAR TO THE ORBIT OF THE EA
             Russia's OPERATIONAL Starwars Defense System
                 Space FAQ 02/15 - Network Resources
                    Space FAQ 04/15 - Calculations
                            What is this ?

    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: 30 Sep 92 23:57:05 GMT
From: _Floor_ <[e-mail]>
Subject: another sad anniversary
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Michael V. Kent) writes:
] Why on earth did they turn them off?  Maybe stop listening for a while, but
      ^^^^^^^^
Ummm...'them' were on the moon.

  _____    "But you can't really call that a dance. It's a walk." - Tony Banks
 /  ___\  ___  __ ___   ___      _____________   [e-mail]
 | / __  / _ \ | /   \ / _ \     |  physics  |   [e-mail]
 | \_\ \ | __/ |  /\ | | __/     |racquetball|   [e-mail]
 \_____/ \___/ |_| |_| \___/     |volleyball |   [e-mail]
 Gene Van Buren, Kzoo Crew(Floor), Washington U. in St. Lou - #1 in Volleyball

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

Date: 30 Sep 92 23:18:51 GMT
From: Kevin Maguire <[e-mail]>
Subject: Clinto and Space Funding
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Gary
Coffman) wrote:
>
> In article <[e-mail]> [e-mail] writes:
> >
> >I would suggest one area that need serious consideration are lung cancer
> >subsidies (ie. the money given to the tobacco producers which goes to subsidise
>
> I can't let this old chestnut pass. Tobacco is the *one* agricultural
> product where growers do *not* receive money from the government. It
> is the one program that works because the government limits the amount
> of tobacco a given producer can sell. This keeps supply low enough that
> it sells at a profit. The government does *not* pay a subsidy to the
> farmer. Instead a clerk at the ACS office fills out a permit once a
> year, about 5 minutes of government clerk time goes to each tobacco
> farmer in the district. That's *it*.
>
       I can't speak to the issue of whether or not direct cash subsidies are
spent on tobacco crops, or whether or not it's proper for the government to

restrict production to keep prices artificially high.
       However, it is a fact that the State Dept. applies enormous pressure,
inlcuding threats of retaliation in other trade areas, to ensure minimum
imports of American cigarettes/tobacco into Southeast Asian countries
despite
the presence of much cheaper local tobacco and serious local government
anti-smoking campaigns.

---------------------------------------------------------------------------
Kevin Maguire                         No, not THAT Kevin Maguire
[e-mail]          I'm a rocket scientist, not an artist

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

Date: 30 Sep 92 23:30:59 GMT
From: Stan Brown <[e-mail]>
Subject: Disney's Man in Space
Newsgroups: sci.space

[e-mail] (Ed McCreary) writes:

>...article deleted for brevity....

>I went down to Johnson a few weeks ago.  In one of the exhibit
>rooms, several monitors were showing the Disney film.  Surrounding
>it was an exhibit of sketches and artwork done for the film.
>Wonderful stuff.

   I Believe that these same films (or excerpts from them) are also
   shown continuosly at the US Space and Rocket center at Huntsville
   Ala.


>--
>In the midst of the word he was trying to say,|[e-mail]
>     In the midst of his laughter and glee,   |Me, speak for Compaq?
>He had softly and suddenly vanished away---   |Yeah, right.
>     For the Snark *was* a Boojum, you see.   |#include <stddisclaimer.h>
--
Stan Brown                        Electric Systems Inc.
Home [phone]                Atalanta Ga. (USA)
Home [phone]                Chattoonaga TN (USA)
Work [phone]                [e-mail]
dixie.com = Public Access UNIX in Georgia

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

Date: 1 Oct 92 00:33:36 GMT
From: John Roberts <[e-mail]>
Subject: Long-term investments
Newsgroups: sci.space

-From: [e-mail] (Nick Szabo)
-Subject: Re: Lunar landing in 2002
-Date: 26 Sep 92 23:51:29 GMT

-In article <[e-mail]> [e-mail] (Gary Coffman) writes:
->...US private industry won't fund
->a return to the Moon because the results won't show up in their bottom
->lines in the less than six months timeframe that institutional investors
->will allow them for venture investments.

-This is silly socialist rhetoric.  Chevron, among others, is planning
-their oil operations in Siberia out beyond 2030 -- forty years.

Then Chevron is to be congratulated. Question: *how much* are they spending
now on projects that won't start to pay for forty years? If it's more than
a few million a year, then I'm *really* impressed.

My impression is that the situation regarding long-term investment by US
business is gradually improving, but that it still has quite a long way to
go before it reaches an "optimum". A privately owned company might have a
better chance in the long run than a public corporation, provided that it
can get the money to invest in the first place.

John Roberts
[e-mail]

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

Date: 1 Oct 92 00:07:10 GMT
From: John Roberts <[e-mail]>
Subject: Population
Newsgroups: sci.space

-From: [e-mail] (Doug Mohney)
-Subject: Re: Population
-Date: 24 Sep 92 18:28:19 GMT
-Organization: Computer Aided Design Lab, U. of Maryland College Park

-In article <[e-mail]>, dudemon@dakine (me ) writes:
->so i would like to rephrase THE QUESTION (tm) in a slightly less homocentric
->manner:
->How many species are you willing to sacrifice to save some humans from a little
->inconvience?

-I suppose we should next try to restore the dinosaurs to the prominance they
-had a couple million years ago?

That's a *little* beyond our current capability. I believe the current
(and recent) record for DNA extraction is ~25 million years, for a termite
trapped in amber. Reconstructing the entire genetic code from DNA fragments
and using that code to produce a living organism are additional challenges.

I'd like to see the restoration of the wooly mammoth. With frozen tissue
available, there's a pretty good chance that they could be cloned.

John Roberts
[e-mail]

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

Date: 30 Sep 92 22:52:42 GMT
From: Carl Hage <[e-mail]>
Subject: Porous Silicon
Newsgroups: sci.energy,sci.space

: In article <[e-mail]>, [e-mail] (Howard Smith) writes:
: > The  "cold-fusion" syndrome seems to be back. On page 33  of  the
: > September  22  issue of Electronic Engineering Times there  is  a
: > report  of a photovoltaic cell which measures 97% efficient.

Not quite. This was measuring the efficiency of a photodetector in being
able to detect photons, not the energy conversion efficiency of a
photovoltaic cell. From the article (actually Sept 21), "We found the MPS
(metal/porous-silicon/silicon) photodiode is comparable in performance to
commercially available silicon photodiodes, but without needing an
anti-reflection coating." ... "Standard silicon photodiodes need
additional surface treatment to keep photons from bouncing off before they
are captured in the silicon lattice. Experiments at SUNY suggest that a
porous-silicon layer is able to trap 100 percent of the photons striking
it eliminating the additional anti-reflection processing step." (Of
course they didn't mention that making porous silicon is an additional
processing step.)

The advance in porous silicon is eliminating the problem of reflection.
In there experiments, the 97% efficient detector had reflection measured
at 2%. The article did not mention an estimated power conversion efficiency
in photovoltaic applications.

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

Date: 30 Sep 92 22:26:06 GMT
From: Patrick Chester <[e-mail]>
Subject: PUTTING VENUS IN AN ORBIT SIMILAR TO THE ORBIT OF THE EA
Newsgroups: sci.space

What about the gas torus that Titan orbits inside of? Isn't that made
up of escaped gas? Would that also affect the atmosphere of Titan?

No flames please, just curious.

--
--------------------------------------------------------------------------------
Patrick Chester            |"The earth is too fragile a basket in which to keep
[e-mail] |  all your eggs." Robert A. Heinlein
Politically Incorrect      |"The meek shall inherit the earth. The rest of us
Future Lunar Colonist      |  are going to the stars." Anonymous
--------------------------------------------------------------------------------

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

Date: 30 Sep 1992 22:10:47 GMT
From: Robert Andrew Knop <[e-mail]>
Subject: Russia's OPERATIONAL Starwars Defense System
Newsgroups: sci.space

[e-mail] (Nick Haines) writes:

>I love this guy. Best laugh of the morning.

Indeed.  And, since it is difficult for others to see in a net post, that
you're a wide eyed, frothing-at-the-mouth lunatic, this guy did a good job of

CAPITALIZING every word that he thought needed EMPHASIS, DAMMIT so that we got
the idea that he was RANTING and RAVING with YOUR TAX DOLLARS!  (Oops, sorry
about that last bit, got carried away.)

-Rob Knop
[e-mail]

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

Date: 30 Sep 92 23:06:39 GMT
From: Jon Leech <[e-mail]>
Subject: Space FAQ 02/15 - Network Resources
Newsgroups: sci.astro,sci.space,news.answers

Archive-name: space/net
Last-modified: $Date: 92/09/30 18:59:19 $

NETWORK RESOURCES

OVERVIEW

    You may be reading this document on any one of an amazing variety of
    computers, so much of the material below may not apply to you. In
    general, however, systems connected to 'the net' fall in one of three
    categories: Internet, Usenet, or BITNET. Electronic mail may be sent
    between these networks, and other resources available on one of these
    networks are sometimes accessible from other networks by email sent to
    special 'servers'.

    The space and astronomy discussion groups actually are composed of
    several mechanisms with (mostly) transparent connections between them.

    One mechanism is the mailing list, in which mail is sent to a central
    distribution point which relays it to all recipients of the list. In
    addition to the general lists for space (called SPACE Digest for
    Internet users, and SPACE on BITNET), there are a number of more
    specialized mailing lists described below.

    A second mechanism is Usenet 'netnews'. This is somewhat like a bulletin
    board operating on each system which is a part of the net. Netnews
    separates contributions into hundreds of different categories based on a
    'group name'. The groups dealing most closely with space topics are
    called 'sci.space.news', 'sci.space', 'sci.space.shuttle', 'sci.astro',
    and 'talk.politics.space'. Contributors 'post' submissions (called
    'articles' in netnews terminology) on their local machine, which sends
    it to other nearby machines. Similarly, articles sent from nearby
    machines are stored locally and may be forwarded to other systems, so
    that an article is posted locally and eventually reaches all the Usenet
    sites interested in receiving the news group to which the article was
    posted.

    Gateway machines serve to redirect Usenet netnews into Internet and
    BITNET mailing lists and vice versa. If you can receive netnews, its
    more flexible interface usually makes it the preferred option to getting
    on one of the main mailing lists.

MAILING LISTS

    SPACE Digest is the main Internet list, and is now being run by the
    International Space University (in only its second change of management
    in over a decade). Email [e-mail] (message body
    should be in the format 'subscribe space John Public') to join. Note
    that the moderated SPACE Magazine list is defunct at present for lack of
    a moderator.

    Elements is a moderated list for fast distribution of Space Shuttle
    Keplerian Elements before and during Shuttle flights. NASA two line
    elements are sent out on the list from Dr. Kelso, JSC, and other sources
    as they are released. Email to [e-mail] to join.

    Space-investors is a list for information relevant to investing in
    space-related companies. Email Vincent Cate ([e-mail]) to join.

    Space-tech is a list for more technical discussion of space topics;
    discussion has included esoteric propulsion technologies, asteroid
    capture, starflight, orbital debris removal, etc. Email to
    [e-mail] to join. Archives of old digests and
    selected excerpts are available by anonymous FTP from
    daisy.learning.cs.cmu.edu (128.2.218.26) in /usr/anon/public/space-tech,
    or by email to space-tech-request if you don't have FTP access.

    SEDS-L is a BITNET list for members of Students for the Exploration and
    Development of Space and other interested parties. Email
    [e-mail] with a message saying "SUBSCRIBE SEDS-L your
    name". Email saying "INDEX SEDS-L" to list the archive contents.

    SEDSNEWS is a BITNET list for news items, press releases, shuttle status
    reports, and the like. This duplicates material which is also found in
    Space Digest, sci.space, sci.space.shuttle, and sci.astro. Email
    [e-mail] saying "SUBSCRIBE SEDSNEWS your name" to join.
    Email saying "INDEX SEDSNEWS" to list the archive contents.

    Ron Baalke ([e-mail]) runs a mailing list which
    carries the contents of the sci.space.news Usenet group. Email him
    to join the list.

    As a general note, please mail to the *request* address to get off a
    mailing list. SPACE Digest, for example, relays many inappropriate
    'please remove me from this list' messages which are sent to the list
    address rather than the request address.

PERIODICALLY UPDATED INFORMATION

    In addition to this FAQ list, a broad variety of topical information is
    posted to the net (unless otherwise noted, in the new group
    sci.space.news created for this purpose). Please remember that the
    individuals posting this information are performing a service for all
    net readers, and don't take up their time with frivolous requests.

    ACRONYMS
    Garrett Wollman ([e-mail]) posts an acronym list around the
    first of each month.

    ASTRO-FTP LIST
    Veikko Makela ([e-mail]) posts a monthly list of
    anonymous FTP servers containing astronomy and space related
    material to sci.space and sci.astro.

    AVIATION WEEK
    Henry Spencer ([e-mail]) posts summaries of
    space-related stories in the weekly _Aviation Week and Space
    Technology_.

    BUYING TELESCOPES
    Ronnie Kon ([e-mail]) posts a guide to buying telescopes to
    sci.astro.

    ELECTRONIC JOURNAL OF THE ASA
    Don Barry ([e-mail]) posts the monthly Electronic Journal
    of the Astronomical Society of the Atlantic to sci.astro.

    ESA BULLETIN
    Harm Munk ([e-mail]) posts summaries of articles in the
    quarterly _ESA Bulletin_ and the _ESA Journal_.

    FLIGHT INTERNATIONAL
    Swaraj Jeyasingh ([e-mail]) posts summaries of
    space-related news from _Flight International_. This focuses more on
    non-US space activities than Aviation Week.

    LARGE ASTRONOMICAL PROJECTS
    Robert Bunge ([e-mail]) posts a list describing many
    "Large Telescope Projects Either Being Considered or in the Works"
    to sci.astro.

    NASA HEADLINE NEWS & SHUTTLE REPORTS
    Peter Yee ([e-mail]) posts a variety of NASA material,
    including NASA Headline News (with the schedule for NASA SELECT),
    shuttle payload briefings and flight manifests, and KSC shuttle
    status reports. For Usenet users, much of this material appears in
    the group sci.space.shuttle.

    NASA UPDATES
    Ron Baalke ([e-mail]) posts frequent updates from
    JPL, Ames, and other centers on the Ulysses, Gailileo, Pioneer,
    Magellan, Landsat, and other missions.

    ORBITAL ELEMENT SETS
    TS Kelso ([e-mail]) posts orbital elements from
    NASA Prediction Bulletins.

    Mike Rose ([e-mail]) posts orbital elements for the Hubble
    Space Telescope to sci.astro.

    Jost Jahn ([e-mail]) posts ephemerides for asteroids,
    comets, conjunctions, and encounters to sci.astro.

    SATELLITE LAUNCHES
    Richard Langley ([e-mail]) posts SPACEWARN Bulletin, which
    describes recent launch/orbital decay information and satellites
    which are useful for scientific activities. Recent bulletins are
    available by anonymous FTP from nssdca.gsfc.nasa.gov in
    ANON_DIR:[000000.ACTIVE.SPX].

    SHUTTLE MANIFEST
    Ken Hollis ([e-mail]) posts a compressed version
    of the Space Shuttle launch manifest to sci.space.shuttle. This
    includes dates, times, payloads, and information on how to see
    launches and landings.

    SOLAR ACTIVITY
    Cary Oler ([e-mail]) posts Solar Terrestrial reports
    (describing solar activity and its effect on the Earth) to
    sci.space. The report is issued in part from data released by the
    Space Enviroment Services Center, Boulder Colorado. The intro
    document needed to understand these reports is available by
    anonymous FTP from solar.stanford.edu (36.10.0.4) in
    pub/understanding_solar_terrestrial_reports. nic.funet.fi
    (128.214.6.100) also has this document in
    /pub/misc/rec.radio.shortwave/solarreports and is an archive site
    for the reports (please note this site is in Europe, and the
    connection to the US is only 56KB). A new primary archive site,
    xi.uleth.ca (142.66.3.29), has recently been established and will be
    actively supported.

    SOVIET SPACE ACTIVITIES
    Glenn Chapman ([e-mail]) posts summaries of Soviet space
    activities.

    SPACE ACTIVIST NEWSLETTER
    Allen Sherzer ([e-mail]) posts a newsletter, "One Small Step for
    a Space Activist," to talk.politics.space. It describes current
    legislative activity affecting NASA and commercial space activities.

    SPACE EVENTS CALENDAR
    Ron Baalke ([e-mail]) posts a calendar including
    anniversaries, conferences, launch dates, meteor showers and
    eclipses, and other space-related events.

    SPACE NEWS
    John Magliacane ([e-mail]) posts "SpaceNews" (covering
    AMSATs, NOAA and other weather satellites, and other ham
    information) to rec.radio.amateur.misc and sci.space.

    SPACE REPORT
    Jonathan McDowell ([e-mail]) posts "Jonathan's Space
    Report" covering launches, landings, reentries, status reports,
    satellite activities, etc.

    TOWARD 2001
    Bev Freed ([e-mail]) posts "Toward 2001", a weekly
    global news summary reprinted from _Space Calendar_ magazine.


WARNING ABOUT NON-PUBLIC NETWORKS

    (Included at the suggestion of Eugene Miya, who wrote the item)

    NASA has an internal system of unclassified electronic mail and bulletin
    boards. This system is not open for public use. Specifically, NASA
    personnel and procurement operations are regarded with some sensitivity.
    Contractors must renegotiate their contracts. The Fair and Open
    Procurement Act does not look kindly to those having inside information.
    Contractors and outsiders caught using this type of information can
    expect severe penalities. Unauthorized access attempts may subject you
    to a fine and/or imprisonment in accordance with Title 18, USC, Section
    1030. If in fact you should should learn of unauthorized access, contact
    NASA personnel.


NEXT: FAQ #3/15 - Online (and some offline) sources of images, data, etc.

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

Date: 30 Sep 92 23:06:51 GMT
From: Jon Leech <[e-mail]>
Subject: Space FAQ 04/15 - Calculations
Newsgroups: sci.astro,sci.space,news.answers

Archive-name: space/math
Last-modified: $Date: 92/09/30 18:59:15 $

PERFORMING CALCULATIONS AND INTERPRETING DATA FORMATS

    COMPUTING SPACECRAFT ORBITS AND TRAJECTORIES

    References that have been frequently recommended on the net are:

    "Fundamentals of Astrodynamics" Roger Bate, Donald Mueller, Jerry White
    1971, Dover Press, 455pp $8.95 (US) (paperback). ISBN 0-486-60061-0

    NASA Spaceflight handbooks (dating from the 1960s)
    SP-33 Orbital Flight Handbook (3 parts)
    SP-34 Lunar Flight Handbook   (3 parts)
    SP-35 Planetary Flight Handbook (9 parts)

    These might be found in university aeronautics libraries or ordered
    through the US Govt. Printing Office (GPO), although more
    information would probably be needed to order them.

    M. A. Minovitch, _The Determination and Characteristics of Ballistic
    Interplanetary Trajectories Under the Influence of Multiple Planetary
    Attractions_, Technical Report 32-464, Jet Propulsion Laboratory,
    Pasadena, Calif., Oct, 1963.

    The title says all. Starts of with the basics and works its way up.
    Very good. It has a companion article:

    M. Minovitch, _Utilizing Large Planetary Perubations for the Design of
    Deep-Space Solar-Probe and Out of Ecliptic Trajectories_, Technical
    Report 32-849, JPL, Pasadena, Calif., 1965.

    You need to read the first one first to realy understand this one.
    It does include a _short_ summary if you can only find the second.

    Contact JPL for availability of these reports.

    "Spacecraft Attitude Dynamics", Peter C. Hughes 1986, John Wiley and
    Sons.

    "Celestial Mechanics: a computational guide for the practitioner",
    Lawrence G. Taff, (Wiley-Interscience, New York, 1985).

    Starts with the basics (2-body problem, coordinates) and works up to
    orbit determinations, perturbations, and differential corrections.
    Taff also briefly discusses stellar dynamics including a short
    discussion of n-body problems.


    COMPUTING PLANETARY POSITIONS

    More net references:

    Van Flandern & Pullinen, _Low-Precision Formulae for Planetary
    Positions_, Astrophysical J. Supp Series, 41:391-411, 1979. Look in an
    astronomy or physics library for this; also said to be available from
    Willmann-Bell.

    Gives series to compute positions accurate to 1 arc minute for a
    period + or - 300 years from now. Pluto is included but stated to
    have an accuracy of only about 15 arc minutes.

    _Interactive Computer Ephemeris_ (from the US Naval Observatory)
    distributed on IBM-PC floppy disks, $35 (Willmann-Bell). Covers dates
    1800-2049.

    "Planetary Programs and Tables from -4000 to +2800", Bretagnon & Simon
    1986, Willmann-Bell.

    Floppy disks available separately.

    "Fundamentals of Celestial Mechanics" (2nd ed), J.M.A. Danby 1988,
    Willmann-Bell.

    A good fundamental text. Includes BASIC programs; a companion set of
    floppy disks is available separately.

    "Astronomical Formulae for Calculators" (4th ed.), J. Meeus 1988,
    Willmann-Bell.

    "Astronomical Algorithms", J. Meeus 1991, Willmann-Bell.

    If you actively use one of the editions of "Astronomical Formulae
    for Calculators", you will want to replace it with "Astronomical
    Algorithms". This new book is more oriented towards computers than
    calculators and contains formulae for planetary motion based on
    modern work by the Jet Propulsion Laboratory, the U.S. Naval
    Observatory, and the Bureau des Longitudes. The previous books were
    all based on formulae mostly developed in the last century.

    Algorithms available separately on diskette.

    "Practical Astronomy with your Calculator" (3rd ed.), P. Duffett-Smith
    1988, Cambridge University Press.

    "Orbits for Amateurs with a Microcomputer", D. Tattersfield 1984,
    Stanley Thornes, Ltd.

    Includes example programs in BASIC.

    "Orbits for Amateurs II", D. Tattersfield 1987, John Wiley & Sons.

    "Astronomy / Scientific Software" - catalog of shareware, public domain,
    and commercial software for IBM and other PCs. Astronomy software
    includes planetarium simulations, ephemeris generators, astronomical
    databases, solar system simulations, satellite tracking programs,
    celestial mechanics simulators, and more.

    Andromeda Software, Inc.
    P.O. Box 605
    Amherst, NY 14226-0605


    COMPUTING CRATER DIAMETERS FROM EARTH-IMPACTING ASTEROIDS

    Astrogeologist Gene Shoemaker proposes the following formula, based on
    studies of cratering caused by nuclear tests.

             (1/3.4)
    D = S  S  c  K  W        : crater diameter in km
     g  p  f  n

           (1/6)
    S = (g /g )            : gravity correction factor for bodies other than
     g      e  t              Earth, where g = 9.8 m/s^2 and g    is the surface
                        e              t
                  gravity of the target body. This scaling is
                  cited for lunar craters and may hold true for
                  other bodies.

        (1/3.4)
    S = (p / p )        : correction factor for target density p  ,
     p      a   t                                t
                  p  = 1.8 g/cm^3 for alluvium at the Jangle U
                   a
                  crater site, p = 2.6 g/cm^3 for average
                  rock on the continental shields.

    C                : crater collapse factor, 1 for craters <= 3 km
                  in diameter, 1.3 for larger craters (on Earth).

                                (1/3.4)
    K                : .074 km / (kT TNT equivalent)
     n                  empirically determined from the Jangle U
                  nuclear test crater.

          3           2               19
    W = pi * d    * delta * V  / (12 * 4.185 * 10  )
                : projectile kinetic energy in kT TNT equivalent
                  given diameter d, velocity v, and projectile
                  density delta in CGS units. delta of around 3
                  g/cm^3 is fairly good for an asteroid.

    An RMS velocity of V = 20 km/sec may be used for Earth-crossing
    asteroids.

    Under these assumptions, the body which created the Barringer Meteor
    Crater in Arizona (1.13 km diameter) would have been about 40 meters in
    diameter.

    More generally, one can use (after Gehrels, 1985):

    Asteroid        Number of objects  Impact probability  Impact energy
    diameter (km)               (impacts/year)       (* 5*10^20 ergs)

     10                10             10^-8        10^9
      1             1 000             10^-6        10^6
      0.1           100 000             10^-4        10^3

    assuming simple scaling laws. Note that 5*10^20 ergs = 13 000 tons TNT
    equivalent, or the energy released by the Hiroshima A-bomb.

    References:

    Gehrels, T. 1985 Asteroids and comets. _Physics Today_ 38, 32-41. [an
    excellent general overview of the subject for the layman]

    Shoemaker, E.M. 1983 Asteroid and comet bombardment of the earth. _Ann.
    Rev. Earth Planet. Sci._ 11, 461-494. [very long and fairly
    technical but a comprehensive examination of the
     subject]

    Shoemaker, E.M., J.G. Williams, E.F. Helin & R.F. Wolfe 1979
    Earth-crossing asteroids: Orbital classes, collision rates with
    Earth, and origin. In _Asteroids_, T. Gehrels, ed., pp. 253-282,
    University of Arizona Press, Tucson.

    Cunningham, C.J. 1988 _Introduction to Asteroids: The Next Frontier_
    (Richmond: Willman-Bell, Inc.) [covers all aspects of asteroid
    studies and is an excellent introduction to the subject for people
    of all experience levels. It also has a very extensive reference
    list covering essentially all of the reference material in the
    field.]


    MAP PROJECTIONS AND SPHERICAL TRIGNOMETRY

    Two easy-to-find sources of map projections are the "Encyclopaedia
    Brittanica", (particularly the older volumes) and a tutorial appearing
    in _Graphics Gems_ (Academic Press, 1990). The latter was written with
    simplicity of exposition and suitability of digital computation in mind
    (spherical trig formulae also appear, as do digitally-plotted examples).

    More than you ever cared to know about map projections is in John
    Snyder's USGS publication "Map Projections--A Working Manual", USGS
    Professional Paper 1395. This contains detailed descriptions of 32
    projections, with history, features, projection formulas (for both
    spherical earth and ellipsoidal earth), and numerical test cases. It's a
    neat book, all 382 pages worth. This one's $20.

    You might also want the companion volume, by Snyder and Philip Voxland,
    "An Album of Map Projections", USGS Professional Paper 1453. This
    contains less detail on about 130 projections and variants. Formulas are
    in the back, example plots in the front. $14, 250 pages.

    You can order these 2 ways. The cheap, slow way is direct from USGS:
    Earth Science Information Center, US Geological Survey, 507 National
    Center, Reston, VA 22092. (800)-USA-MAPS. They can quote you a price and
    tell you where to send your money. Expect a 6-8 week turnaround time.

    A much faster way (about 1 week) is through Timely Discount Topos,
    (303)-469-5022, 9769 W. 119th Drive, Suite 9, Broomfield, CO 80021. Call
    them and tell them what you want. They'll quote a price, you send a
    check, and then they go to USGS Customer Service Counter and pick it up
    for you. Add about a $3-4 service charge, plus shipping.

    A (perhaps more accessible) mapping article is:

    R. Miller and F. Reddy, "Mapping the World in Pascal",
    Byte V12 #14, December 1987

    Contains Turbo Pascal procedures for five common map projections. A
    demo program, CARTOG.PAS, and a small (6,000 point) coastline data
    is available on CompuServe, GEnie, and many BBSs.

    Some references for spherical trignometry are:

    _Spherical Astronomy_, W.M. Smart, Cambridge U. Press, 1931.

    _A Compendium of Spherical Astronomy_, S. Newcomb, Dover, 1960.

    _Spherical Astronomy_, R.M. Green, Cambridge U. Press., 1985 (update
    of Smart).

    _Spherical Astronomy_, E Woolard and G.Clemence, Academic
    Press, 1966.


    PERFORMING N-BODY SIMULATIONS EFFICIENTLY

    "Computer Simulation Using Particles"
    R. W. Hockney and J. W. Eastwood
    (Adam Hilger; Bristol and Philadelphia; 1988)

    "The rapid evaluation of potential fields in particle systems",
    L. Greengard
    MIT Press, 1988.

        A breakthrough O(N) simulation method. Has been parallelized.

    L. Greengard and V. Rokhlin, "A fast algorithm for particle
    simulations," Journal of Computational Physics, 73:325-348, 1987.

    "An O(N) Algorithm for Three-dimensional N-body Simulations", MSEE
    thesis, Feng Zhao, MIT AILab Technical Report 995, 1987

    "Galactic Dynamics"
    J. Binney & S. Tremaine
    (Princeton U. Press; Princeton; 1987)

        Includes an O(N^2) FORTRAN code written by Aarseth, a pioneer in
        the field.

    Hierarchical (N log N) tree methods are described in these papers:

    A. W. Appel, "An Efficient Program for Many-body Simulation", SIAM
    Journal of Scientific and Statistical Computing, Vol. 6, p. 85,
    1985.

    Barnes & Hut, "A Hierarchical O(N log N) Force-Calculation
    Algorithm", Nature, V324 # 6096, 4-10 Dec 1986.

    L. Hernquist, "Hierarchical N-body Methods", Computer Physics
    Communications, Vol. 48, p. 107, 1988.


    INTERPRETING THE FITS IMAGE FORMAT

    If you just need to examine FITS images, use the ppm package (see the
    comp.graphics FAQ) to convert them to your preferred format. Failing
    that, the basic reference for FITS may be found in the following 3
    papers:

    Wells, D. C., Greisen, E. W., and Harten, R. H., "FITS: a
    flexible image transport system," Astronomy and Astrophysics
    Supplement Series, 44, 363-370, 1981.

    Grosbol, P., Harten, R. H., Greisen, E. W., and Wells, D. C.,
    "Generalized extensions and blocking factors for FITS,"
    Astronomy and Astrophysics Supplement Series, 73, 359-364, 1988

    Harten, R. H., Grosbol. P., Greisen, E. W., and Wells, D. C.,
    "The FITS tables extension, Astronomy and Astrophysics
    Supplement Series, 73, 365-372, 1988.

    A DRAFT document describing FITS and the Floating Point Agreement
    defining FP storage formats is available by anonymous FTP from
    nssdca.gsfc.nasa.gov (128.183.36.23). Get ANON_DIR:[FITS]README.;1 to
    begin with. There are known to be errors and ambiguities in this
    document, so it should not be used as a fundamental reference. Questions
    should be sent by email to the FITS support office
    ([e-mail]) or telephone at (301)-513-1634

    A FORTRAN library for reading and writing FITS files is available by
    anonymous FTP from tetra.gsfc.nasa.gov (128.183.8.77) in directory
    pub/fitsio3. Contact the author, William Pence
    ([e-mail]) for more details.


    SKY (UNIX EPHEMERIS PROGRAM)

    The 6th Edition of the Unix operating system came with several software
    systems not distributed because of older media capacity limitations.
    Included were an ephmeris, a satellite track, and speech synthesis
    software. The ephmeris, sky(6), is available within AT&T and to sites
    possessing a Unix source code license. The program is regarded as Unix
    source code. Sky is <0.5MB. Send proof of source code license to

    E. Miya
    MS 258-5
    NASA Ames Research Center
    Moffett Field, CA 94035-1000
    [e-mail]


    THREE-DIMENSIONAL STAR/GALAXY COORDINATES

    To generate 3D coordinates of astronomical objects, first obtain an
    astronomical database which specifies right ascension, declination, and
    parallax for the objects. Convert parallax into distance using the
    formula in part 6 of the FAQ, convert RA and declination to coordinates
    on a unit sphere (see some of the references on planetary positions and
    spherical trignometry earlier in this section for details on this), and
    scale this by the distance.

    Two databases useful for this purpose are the Yale Bright Star catalog
    (sources listed in FAQ section 3) or "The Catalogue of Stars within 25
    parsecs of the Sun" (in pub/SPACE/FAQ/stars.data and stars.doc on
    ames.arc.nasa.gov).


NEXT: FAQ #5/15 - References on specific areas

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

Date: 30 Sep 92 22:52:50 GMT
From: Carl Hage <[e-mail]>
Subject: What is this ?
Newsgroups: sci.space

[e-mail] writes:
: Have the U.S. some kind of RPV with such performances ?
:
:  Seconds after    Heading                    Speed    Altitude
:    lock-on       (degrees)                  (knots)    (feet)
:
:       00            200                       150       7000
:       01            200                       150       7000
:       02            200                       150       7000
:       03            200                       150       7000
:       04      sharp 200          acceleration 150       6000
:       05       turn 270             = 22 g    560       6000
:       06            270                       560       6000
:       07            270                       570       6000
:       08            270                       560       7000
:       09            270                       550       7000
:       10            210                       560       9000

It must have a warp drive since it managed 1000 feet of altitude change
while going only 150 knots (253 f/s). Does anybody know what kind of
accelerations are typical in an air-air or ground-air missle? What
about a MARV ICBM reentry vehicle?

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

End of Space Digest Volume 15 : Issue 268
------------------------------