Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_5/V11_540.TXT

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Subject: SPACE Digest V11 #540

SPACE Digest                                     Volume 11 : Issue 540

Today's Topics:
         Re: Aim For The Moon - model rocket contest
               Re: Model rocket contest
             Re: Weather Satellite Photos
             Re: Weather Satellite Photos
           Hubble Space Telescope Update - 06/14/90
               Re: 10 psi overpressure
                  SpaceList

Administrivia:

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

Date: 18 Jun 90 18:41:42 GMT
From: att!cbnewse![e-mail]  (kevin.w.mckiou)
Subject: Re: Aim For The Moon - model rocket contest

In article <[e-mail]> [e-mail] (Vincent Cate) writes:
>
>1992 marks the 500 year anniversary of Columbus' trip to America.  It
>would be fun to commemorate this with an "Aim for the moon" model rocket
>contest.  The goal of the contest could be to get a small transmitter near
>the moon as cheaply as possible

Geezzz...couldn't we start with orbiting the earth?

Somebody want to volunteer to get the FAA clearance? :-)

Kevin

---------------------------------------------------------------------
Kevin McKiou                         UUCP:     att!ihlpy!kwm
NAR 51581
AT&T Bell Labs, Naperville, Ill      Internet: [e-mail]
---------------------------------------------------------------------

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Date:         Mon, 18 Jun 90 15:28:05 CDT
From: John Nordlie <[e-mail]>
Subject:      Re: Model rocket contest


>From: sam.cs.cmu.edu![e-mail]  (Vincent Cate)
>Subject: Aim For The Moon - model rocket contest


>1992 marks the 500 year anniversary of Columbus' trip to America.  It
>would be fun to commemorate this with an "Aim for the moon" model rocket
>contest.  The goal of the contest could be to get a small transmitter near
>the moon as cheaply as possible (cost could be measured as total
>newton-seconds of thrust for all stages).  The only restrictions would be
>that only off the shelf "model rocket motors" could be used and that the
>standard transmitter must be in the payload.  I think this limits people
>to using "N" or smaller rockets.

>It seems that using a small rocket to send a small transmitter to the
>moon would be very possible.  It would take a rocket with a number of
>stages starting with the larger size motors; however, I think you could do
>it without going so far as making a 10 stage rocket that starts with
>multiple "N"s.

This sounds like a very neat idea, if it can be done.  However, I have
some difficulty believing that a gun powder (model rocket engine
propellant is basically gun powder, with some other burn-controlling
chemicals added) rocket could achieve escape velocity, starting from
the earth's surface.  I remember reading in a book on rockets and
jets that a gun powder powered rocket the size of a Saturn V cound
not reach escape velocity.  The chemical potential energy per unit
weight is simply not high enough.

I have never heard of an "N" model rocket engine ("A" - "F" yes,
but not "N"), so I may be wrong about the fuel used in them.  If these
"N" engines were to use a suitably volatile solid fuel, it MIGHT
be possible to get one into LEO, or better.

>One might be the "cheapest" rockets to get within 100,000
>miles of the moon and go beyond the orbit of the moon.  Another might be
>for the rockets that come the closest to the center of the side of the
>moon facing us (crash landings ok).  Another might be for the shortest
>trip time.  Another might be for the cheapest to escape the Earth's
>gravitational field.

That's annother point: guidance.  I was just out today flying a
model rocket with a camera in the nose, and could not get the thing
to fly the direction I wanted it to no matter what I tried.  The rocket
kept turning into the wind after takeoff (this makes perfect sense if
you know a little about aerodynamics.  ie: weather vane).  I know
of no simple guidence system that would keep a rocket on course
(or even going straight up) while it travels through the atmosphere.
A simple guidance system using gyros would probably be too heavy
(or, if a very light one were made, too expensive).

My final argument is this:  There are many universities, organizations,
and private individules out there who would love to do some space
science.  If it is possible to get very small payloads out of earth's
gravity well using extremly cheap (compaired to comercial launch)
off the shelf rocket parts, why hasn't anyone done it already?  I know
that "It's never been done, so it can't be done" is not a valid or
logical argument, but don't you think someone would already be doing
it now?

(It's still a really neat idea, though!)
------------------------------------------------------------------------
John Nordlie      :     (Sorry, I couldn't come up with any clever
                  :      message/quote/disclaimer today)
------------------------------------------------------------------------

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

Date: 18 Jun 90 17:35:45 GMT
From: [e-mail]  (Kevin William Ryan)
Subject: Re: Weather Satellite Photos


   I have talked to the person responsible for the archive I use - they are
upgrading their net link from 56Kb to 1.5Mb in the next week or two.  When they
have done so I will post the various GIF program directory listings and the
address for anonymous FTP.  These are GIF readers for all sorts of CPU's; IBM,
Mac, X-windows, etc...

   In regards to bandwidth problems involved in opening FTP to all sorts of
sat data, perhaps a poll should be taken to see what the most desired photos
are.  For me that would be daily Eastern US weather shots (preferably taken
at the same time of day so I could view them as a series), and possibly the
occassional IR shot for comparison.  Would it be possible to offer some images
via request for the less commonly desired shots, such as (for example) IR and
ozone readings for the Southern Pacific?

                                                 kwr

P.S.  Until I get the OK to publicize the archive I mentioned, please go ahead
and hunt up your own sources for GIF and other image reading programs...

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

Date: 18 Jun 90 15:29:44 GMT
From: [e-mail]  (Kevin William Ryan)
Subject: Re: Weather Satellite Photos


   One thing that probably should be done to reduce bandwidth is to compress
the images.  There are several possible ways to do this - I would suggest using
the GIF (general image format) compression scheme, put together by the
Compuserver folks, which is a slightly modified Lempel-Ziv compression
algorithm.  Depending on image complexity compression reduces image size by
10-90%, with an average of about 40%.  Note that there are a variety of GIF
format read/display programs available, freeware and otherwise, for almost
any machine types.  (I suggest looking at users groups, Compuserve sources,
public archives, etc.)  This is a reasonably widely used format.  For sending
via text-only channels (such as mail) the GIF or otherwise compressed image
can be uuencoded into ascii.  This expands the image size by about 30%, though,
and the image usually will have to be broken into several pieces to be sent
through most mail systems.

   I am extremely hesitant to list the one or two places I know of where the
public domain GIf readers are stored - thus causing several thousand people to
try to access them at once.  I therefore am publicly requesting the people
running such archives to list themselves if they are agreeable.  In the
meantime I can give several pointers - look for the Mac programs QuickGIF and
Giffer, check the same archives that have NCSA Telnet, NIH Image, and other
freeware, and read the alt.sex.pictures UseNet group, where they have been
discussing GIF format images for a month or two; including Sun, X11, IBM, and
Mac programs.

                                                     kwr

Internet: [e-mail]

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

Date: 17 Jun 90 19:06:09 GMT
From: usc!jarthur!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Hubble Space Telescope Update - 06/14/90


                      Hubble Space Telescope Update
                             June 14, 1990


     Bootstrap Phase B part 3, coarse wavefront measurements, finished on
June 10.  The data obtained from this test was felt adequate enough to
provide an improvement in focus but not in alignment.  Data from the
independent measurements did not fully agree on where the focus was so a
decision was made to go with the determination that had the best
Signal-to-Noise Ratio (SNR).  A command was issued to move the mirror 24
microns (less than 1 wave) or equivalent to ~0.5 arcsec change in the image.
Planetary Camera (PC) pictures were then obtained.  These new "after" images
look different from the "before" image, but most of the difference is due to
a small attitude change that was put in to move a bright star to the center
of the image.  Quantitative analysis of the image show no statistically
significant difference between the two images.  The likely explanation of
this lack of difference was that the secondary was moved too much; it was
moved through focus to a position roughly the same distance from focus, but
on the other side of focus, as it was before the movement.  The next phase of
the focusing process, Bootstrap Phase B part 4, Exit Pupil Calibration,
begins on June 12 and runs through June 15.  The expectation is that after
this test the mirror will be moved in focus and aligned.  More PC pictures
will be obtained on June 15.

     The Faint Object Spectrograph (FOS) is in the process of slowly turning
their High Voltage (HV) on, all is going well so far. The High Speed
Photometer (HSP) is running Detector Dark Count tests, Detector 4 tests have
finished, Detector 1 testing is still in progress.  So far, no anomalies have
been reported.

     No new results from the analysis of the Pointing Control Subsystem (PCS)
problems.  Fixed Head Star Tracker (FHST) testing will be occurring a few
times per week for a while.  The Wide Field Planetary Camera (WFPC) is in
full operate mode. There will be more pictures this week in support of
Bootstrap Phase B focus and alignment.
       _   _____    _
      | | |  __ \  | |       Ron Baalke           |  [e-mail]
      | | | |__) | | |       Jet Propulsion Lab   |  [e-mail]
   ___| | |  ___/  | |___    M/S 301-355          |
  |_____/ |_|      |_____|   Pasadena, CA 91109   |

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

Date: 18 Jun 90 18:38:03 GMT
From: clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: 10 psi overpressure

In article <[e-mail]> [e-mail] (Carl Gooch) writes:
>...The force of the explosion was, I'm pretty sure, what
>destroyed the Orbiter; it wasn't designed to take the stress of a
>detonation wave hitting its bottom surface.

Sorry, wrong; there was no explosion.  The external tank fell apart,
and the fuel burned, but there was no detonation and the orbiter was
not particularly damaged by the fire.  It was destroyed because the
tank breakup threw it violently out of control in a Mach 3 slipstream,
and its structure simply isn't strong enough to take that.  It flies
forward just fine, but flying sideways is out of the question even for
jet fighters, and they are much tougher than shuttle orbiters.

A closer reading of the Rogers Commission report will give you the details.
--
As a user I'll take speed over|     Henry Spencer at U of Toronto Zoology
features any day. -A.Tanenbaum| uunet!attcan!utzoo!henry [e-mail]

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

Date: Mon, 18 Jun 90 09:41:34 PDT
From: [e-mail]
X-Vmsmail-To: UTADNX::UTSPAN::AMES::"[e-mail]"
Subject: SpaceList

Space List: What every Space Enthusiast Should Know

A List of Numbers and Equations Relevant to Space Exploration
  courtesy Dale M. Greer

Update 4: 18-JUN-1990 Solar info from Liam E. Gumley
Update 3: 23-MAY-1990 Rocketry info from Dave Newkirk

Numbers
   9.8 m/s^2       (  10) -- Acceleration at surface of Earth (one g)
  7726 m/s         (8000) -- Earth orbital velocity at 300 km altitude
  3075 m/s         (3000) -- Earth orbital velocity at 35786 km (geosync)
  6371 km          (6400) -- Mean radius of Earth (Re)
  6378 km          (6400) -- Equatorial radius of Earth (Re)
  1738 km          (1700) -- Mean radius of Moon (Rm)
  5.974e24 kg      (6e24) -- Mass of Earth (Me)
  7.348e22 kg      (7e22) -- Mass of Moon (Mm)
  1.989e30 kg      (2e30) -- Mass of Sun (Ms)
  3.986e14 m^3/s^2 (4e14) -- Gravitational constant times mass of Earth
  4.903e12 m^3/s^2 (5e12) -- Gravitational constant times mass of Moon
  1.327e20 m^3/s^2 (13e19) - Gravitational constant times mass of Sun
  384401 km        ( 4e5) -- Mean Earth-Moon distance
  1.496e11 m       (15e10) - Mean Earth-Sun distance (Astronomical Unit)
  1371 W/m^2       (1400) -- Mean solar constant at 1 AU
  6.672e-11 m^3/(kg*s^2)  -- Universal gravitational constant
 3.08 e13 km    parsec
 9.46 e12 km    light year
 0.46 km/s    Speed of Earth's rotation at equator
 3.0  e8 m/s    Speed of light in a vacuum

Conversions
  1.61   km / mi
  0.0254 m / in
  3.28   ft / m
  0.3048 m / ft
  1.467  fps / mph  (or 88 fps = 60 mph, exactly)
  0.447  m/s / mph
  2.2    lb / kg  (2.2 pounds-mass, that is)

Comparisons
  1 MJ = 0.28 kW hr

Equations
  Where d is distance, v is velocity, a is acceleration, t is time.

  For constant acceleration
    d = d0 + vt + .5at^2
    v = v0 + at
    v^2 = 2ad

  General Gravity
    f = G m1 m2 / r^2
    a = v^2 / r
    g = G Me / r^2

  Escape velocity is the critical speed you need to achieve orbit:
    sqrt(g R) or sqrt(2 G M / R)

  For circular Keplerian orbits, where u is gravitational constant, a is
    semimajor axis of orbit, P is period.
      v^2 = u/a
      P = 2pi/(Sqrt(u/a^3))

  Orbital eccentricity is:
    e = (apogee - perigee) / 2 r, where r is the average orbital radius.


  Rocketry

  The famous delta-v equation for how much velocity you get for burning a
  portion of fuel is:
    Dv = Ve LOGe(Mi / Mf), where Ve is the exhaust velocity,
                     Mi is the initial mass,
                     Mf is the final mass

  This can also be expressed by replacing Ve by g * Isp, where Isp is the
  specific impulse of the fuel.

  Here is a different form of the delta-v equation:
    Dv = Ve LOG(t0 / (t0 - t)), where t0 is the time when all the fuel
                    will be exhausted, and t is the start time.

  This give the displacement of a constantly accelerating rocket:
    d = c^2 / a COSH(at/c - 1), where a is acceleration,
                      t is the subjective time,
                      c is speed of light

  With long time spans and/or high accelerations, this demonstrates special
  relativity in action.  [ Note that COSH(x) = (e^x + e^-x)/2 ]

  The thrust of a rocket engine can be approximated by:
    2 A (p - p0), where A is the minimum nozzle area,
                p is the chamber pressure,
                p0 is the pressure outside the engine

  Or by:
    Ve * F, where F is the rate of fuel use

  Miscellaneous
      f = ma -- Force is mass times acceleration
      w = fd -- Work (energy) is force times distance

  Atmospheric density varies as exp(-mgz/kT) where z is altitude, m is
  molecular weight in kg of air, g is acceleration of gravity, T is
  temperature, k is Bolztmann's constant.  Up to 100 km,
    d = d0*exp(-z*1.42e-4)
  where d is density, d0 is density at 0km, is approximately true, so
    d@12km (13000 m -- 40000 ft) = d0*.18
    d@9 km ( 9800 m -- 30000 ft) = d0*.27
    d@6 km ( 6500 m -- 20000 ft) = d0*.43
    d@3 km ( 3300 m -- 10000 ft) = d0*.65

  Quantity                  Definition        Units

  Energy                    Q                 Joules (J)
  Flux                      dQ/dt             Watts (W)
  Irradiance                dQ/(dt*dA)        W per square meter (W/m^2)
  Monochromatic irradiance  dQ/(dt*dA*dl)     W/m^2 per micron (W/m^2/um^1)
  Radiance                  dQ/(dt*dA*dl*du)  W/m^2/um^1 per steradian
                                              (W/m^2/um^1/sr^1)
  Flux at sun surface = 3.92e+26  Watts

Selected Planetary Data

        Semimajor Axis   Sidereal Synodic Incl.to Grav.Cst.       Mass
                           Period  Period Eclipt. GM (10^12
          (AU)   (Mm)     (Tr.Y.)  (Days)   (deg)  m^3/s^2)    10^24kg
Mercury  0.3871   57.9    0.24085  115.88  7.0042     22.03    0.33022
Venus    0.7233  108.2    0.61521  583.92  3.3944    324.86    4.8690
Earth    1.0000  149.6    1.00004                    403.50    6.0477
Mars     1.5237  227.9    1.88089  779.94  1.8500     42.83    0.64191
Jupiter  5.2028  778.3   11.86223  398.88  1.3047 126712.0  1899.2
Saturn   9.5388 1427.0   29.4577   378.09  2.4894  37934.0   568.56
Uranus  19.1819 2869.6   84.0139   369.66  0.7730   5803.2    86.978
Neptune 30.0578 4496.6  164.793    367.49  1.7727   6871.3   102.99
Pluto   39.44   5900    247.7      366.73 17.17        1       0.012

The Moon         384.4   27.3217days                   4.90    0.073483


(Suggestions?  Favorite numbers, equations?)

_____________
Dale M. Greer
Center for Space Sciences, U.T. at Dallas, UTSPAN::UTADNX::UTDSSA::GREER

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End of SPACE Digest V11 #540
*******************