Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_4/V15NO401.TXT

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Date: Mon,  9 Nov 92 05:07:09
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #401
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Space Digest                Mon,  9 Nov 92       Volume 15 : Issue 401

Today's Topics:
                     2nd Annual AUSROC Conference
                      Comet deflection & mining
                        NASA Coverup (5 msgs)

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

Date: 9 Nov 92 20:19:49 GMT
From: [e-mail]
Subject: 2nd Annual AUSROC Conference
Newsgroups: sci.space,rec.models.rockets

2nd ANNUAL AUSROC CONFERENCE

Signal Processing Research Institute
University of South Australia - Levels Campus
9-11 December 1992

PROGRAM TIMETABLE

WEDNESDAY 9th December
9.00am  Opening                    M. Blair (DSTO)

AUSROC II Launch Campaign Review
9.10   Ausroc II Post Mortem            T. Chen (Ardebil)
9.30   Launch Operations - A Range User's    W. Williams (DSTO)
       Perspective
9.50   Flight Electronics - a Critical Review    J.Colemen
10.10  Ausroc II - The Next Generation            M. Blair (DSTO)
10.30  Morning Tea

AUSROC III Systems Descriptions
Propulsion
11.00      A3 Propulsion System & Components    M.Blair (DSTO)
11.20      A3 Injector & Ignition System        W.Williams DSTO

Structures
11.40      Composite Propellant Tanks            G.Reddon (Adl. Uni.)
12.00      Nose Cone / Fairings            S.Mitchell

Systems Analysis
12.20      Aerodynamic Analysis                 N.O'shea (RMIT)
12.40      Dynamic Analysis            R.Coning (RMIT)
1.00      Lunch
2.00      Trajectory Simulation            T.Winks (QUT)

Control Systems
2.20      Inertial Navigation System        A.Cheers (Ardebil)
2.40      INS Alignment Procedures        M.Pszczel (DSTO)
3.00      Motor Gimbal System            Adl. Uni.
3.20      Afternoon Tea
3.50    Auto-Pilot Algorithm            A.Burridge (Monash)
                        A.Coia (Monash)
                        R.Graham (DSTO)
Flight Electronics
4.10    Data Aquisition System                G.Hermann (U.SA)
                        S.Pietrobon (U.SA)

Ground Support
4.30    Launcher Infrastructure                P.Pemberton (USQ)
                        F.Jacobson (USQ)
                        D.Miller (USQ)
                        F.Naseasi (USQ)
                        A.Ried (USQ)

THURSDAY 10th December
9.00am    Launch Control Sequencer        T.Chen (Ardebil)
9.20    Static Motor Test Facility            R.Bromfield (ARE)

Payload
9.40    Experimental Payloads                I.French (ANU)
10.00    Payload Recovery System                P.Siaw (RMIT)
10.20    Morning Tea

Range Safety
10.50    Operations at the Woomera        W.Williams (DSTO)
    Rocket Range
11.10    Impact Prediction & Tracking            P.Wilson (QUT)
11.30    Flight Termination System        C.Biggs (DSTO)
11.50    Insurance Issues            K.Ikin (GIO)
                        W.Jones (ASIG)
12.10    Lunch

AUSROC IV
1.30    Ausroc IV - Orbital Capability            M.Blair (DSTO)

ASERA Projects
2.00    The Caratel Rocket Project        I. Bryce (HDH)
2.20    'Australis' - Amateur Satellite            C. Lindley (CSIRO)
    Project
2.40    Appropriate Quality Systems for            G.Coote (Hard Copy)
    Amateur Projects
3.10    Afternoon Tea

QLD Scramjet Project
3.40    Qld Uni. Student Scramjet Project    Qld.Uni.

FRIDAY 11th December

Commercial & Government Programs
9.00    "The Australian Space Program"            Ed Cory (ASO)
9.30    "Space Industry Development
    - An Integrated Business"            J.Douglas (SA Gov't.)
10.00    Morning Tea
10.30    "The Southern Launch Vehicle"            I.Touhy (B.Ae.Aust)
                        I.Bryce (HDH)
                        P.Arthur (Auspace)
12.00    "The RASS Small Satellite Project"      S.Pietrobon (U.SA)
12.30pm    Closing                    M. Blair (DSTO)
12.40    Lunch

Post-Conference Tour - WOOMERA ROCKET RANGE
        Friday 2.00pm Depart Adelaide (6hr drive)
        Saturday 9.00am Tour Woomera Range Facilities
        Sunday 10.00am Return to Adelaide

     The AUSROC Conference is free of charge and we extend an open invitation
to anyone with an interest in Aerospace activities in Australia to attend. The
Conference presents an opportunity for all those involved in the Ausroc
Program, around Australia, to get together in one location to present papers
and exchange information and ideas. Those interested in attending the Post
Conference Woomera Tour should reply in writing to Ausroc Projects as numbers
are required for organisational purposes.

Ausroc Projects, 42 Broadmeadows Rd. Elizabeth Nth SA  5113
Ph/Fax : [phone]


Previous AUSROC updates can be obtained by anonymous ftp to
audrey.levels.unisa.edu.au in directory space/AUSROC

--
Steven S. Pietrobon,  Australian Space Centre for Signal Processing
Signal Processing Research Institute, University of South Australia
The Levels, SA 5095, Australia.      [e-mail]

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

Date: 9 Nov 92 03:05:53 GMT
From: Nick Szabo <[e-mail]>
Subject: Comet deflection & mining
Newsgroups: sci.space,alt.sci.planetary

Deflecting anything but the strongest nickle-iron asteroid
with a nuclear explosive is questionable.  Many asteroids are
probably rubble piles, not single big rocks, and comets are so
fragile we've seen some calve off big chunks and obliterate themselves
just from internal gas pressure.  For a comet, farting can be suicide!
For best results use a large number of low-yield devices over a long
period.

10^11 tonnes about equals the annual U.S. consumption of
fresh water, so P/Swift-Tuttle wouldn't make make much difference
down here even if you could get it through the atmosphere
without damaging things.  A much better use is Earth orbit,
in suitably small wrapped pieces.  If we're to have any significant
manufacturing industry in space, we're going to need tons of volatiles.
For example, here is the water used to make various kinds of products
on earth:

            gallons/unit
            ------------
finished steel, ton    40,000
automobiles, unit    12,000
trucks, buses, unit    20,000
ref: Mark's Standard Handbook for Mechanical Engineers, 1987

Presumably we could economize and recycle more than we do on Earth,
but life is much nicer when there's a lot of water handy -- not to
mention the nitrogen, methane, etc. found mainly on comets.  Also
not included in those figures is the copious amount of air for cooling
and lubrication assumed by most industrial processes, eg milling.
Furthermore, most of the mass launched into space is propellant
for orbit-transfer and stationkeeping.  We can easily convert from comet
ice to various kinds of propellant or use as is in thermal rockets.

P/Swift-Tuttle at 50 km/s delta-v is extremely difficult
to get to.  It doesn't make sense to try to capture it; there
are many Jupiter-family comets with periods of 3.5-6 years
and only 8-10 km/s away.  There may be ice closer still in
some of the "mini-asteroids" or larger Apollo-Amors, but that
requires more exploration to confirm or eliminate.

With automated equipment we form a reasonably pure cylindrical
ice shape, attach a small thermal rocket, and capture over 10% of
that ice mass into Earth orbit, or 25% into Mars orbit, while
expelling the rest as thermal rocket exhaust.  Moving the same mass
of material from a gravity well would require rocket with five or
more orders of magnitude power.  Economics hinge on the mass-thruput
ratio of the extraction equipment, which could be similar to water-wells
and ice-makers on Earth.  At around 2,000:1 MTR it becomes economical
to capture Jupiter-family comet ice into Earth orbit.

Back to the P/Swift-Tuttle deflection problem.

If upper-stage technology advances sufficiently over the next 30-40
years, eg magsails powered by the solar wind + a very advanced nuclear
electric second stage, we might be able to catch up with P/Swift-Tuttle
at perihelion in 2057 to track it.  Alternately, we might develop very
good telescopes capable of tracking it that far out, eg huge microgravity-
based reflectors combined with optical interferometry.  Who knows what
technology we will have after 2100, but one possibility is to focus
sunlight with a large parabolic mirror over the period of several
months to change the time P/Swift-Tuttle crosses earth orbit by one day.
Even with this gentle method, we need to gaurd against the possibility
of disrupting the comet rather than deflecting it.  Rendesvous with 50 km/s
incoming will also be a challenge, perhaps several years with a tacking
magsail.



--
Nick Szabo                     [e-mail]

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

Date: 8 Nov 92 18:27:45
From: Craig Powderkeg DeForest <[e-mail]>
Subject: NASA Coverup
Newsgroups: alt.conspiracy,sci.space

In a rather misleading article, [e-mail] (Gary Coffman) writes:
   In article <foo> [e-mail] writes:
   > Dillon Pyron writes:
   >> To  the point.  Your calculations assume that the earth and moon have the
   >> same density, and that it is homogenous.
   >Beiser states , on page 118 , "A spherical object behaves  gravitationally
   >as  if  it's  mass  were concentrated at it's center"

   Beiser's assumption holds up as a close approximation when the two bodies
   are far enough apart that their radius is an insignificant part of their
   separation distance, say Earth-Sun distance. But they fail miserably when
   the separation is less than a few body radiuses. The mascons will warp the
   orbit of the satellite a measurable amount.

Actually, Beiser's assumption holds up extremely well, for snarfy's purposes.
The gravitational force from, say, the Earth on a small test mass near it
is the integral over the entire volume of the Earth of the pull from each
little chunk of mass inside the Earth.  With the assumption that the Earth
is homogenous, the integral can be done in closed form, easily.  One finds
that the pull is the same as that of a point mass at the center of the Earth.

If the mascons had a significant effect (say, 10%) on the local gravity
somewhere in the Earth's neighborhood, we'd find significant `mountains' in
the middle of the ocean.  While mascons do cause small (I seem to recall
order of 50') changes in sea level in certain places, a 10% shift in local
gravity at the surface would result in a change in sea level of the order
of (R-sub-earth) * (10%)^2, or about 50 miles, much higher than Mt. Everest!

Since we don't see 50-mile humps in the ocean (the CRC lists Earth's minimum
radius [the polar one] at 6357 miles, and maximum [equatorial] at 6379 miles),
we can assume that, to within better than 10%, the Earth is a homogeneous
sphere.  QED.

   The existance of tides is a direct result of the effect
   of differentials in gravitational potential across the diameter of a
   body. Using Beiser's simplifing assumption, there could be no tides on
   Earth. Since we can easily observe that there are, his assumption is
   invalid for bodies as close together as the Earth and the Moon.


This is plain wrong.  Using Beiser's simplifying assumption, there could be
tides on Earth.  The tides are due to the fact that the parts of the Earth
closer to the Moon are, well, closer to the Moon and therefore attracted more
strongly than those farther from it.  This is true for every point mass in
the Earth's vicinity, including Gary Coffman, who (if he lives in the
United States) attracts the Empire State Building considerably more than he
does the Opera House in Sydney.

   The other assumption Beiser uses is that of spherical objects. Neither
   the Earth nor the Moon are spheres. The Earth is an oblate spheriod, and
   the Moon is somewhat pear shaped with the greatest mass on the side facing
   Earth. This is again significant when the separation distance is a few
   planetary radiuses.

It's not significant unless the separation distance is less than a few times
the deviation from a sphere, considerably less than a planetary radius!

   The most damning evidence against your theory that the Moon has a
   gravity of .6 G is that we know the orbital period of the Moon to
   a great accuracy, and we know the mass of the Earth and the distance
   to the Moon. With those three numbers, we can calculate exactly how
   much centrifigual force is in the system, and thus how much gravitational
   force is required to counterbalance it. So if the Moon stays in orbit,
   and it does, we can state it's gravitational pull to a high degree of
   accuracy.

This is semi-right, but I'm not sure whether Mr. Coffman understands exactly
what he's saying.  If we assume that the Earth is much more massive than the
Moon, then knowing the distance to the moon and the mass of the Earth tells us
nothing about the mass of the moon.  The reason is that, with Me >> Mm, the
Moon could be made out of lead or out of papier-mache, and it would orbit with
the same period: the heavier the Moon is, the harder the Earth must pull it
to keep it in orbit; but the harder the Earth *does* pull it.

This is one of the great puzzles of Physics -- that gravitational `charge'
should be exactly the same quantity as inertial `mass', so that the mass
of an object is irrelevant to its trajectory through a fixed gravitational
field.  It is one of the reasons why most physicists believe Einstein's
theory of General Relativity, which unifies the ideas of gravity and inertia
on a macroscopic level.

If we start looking at the system more carefully, we note that the Moon doesn't
revolve around the exact center of the Earth, but that both the Earth and Moon
revolve around a point somewhere above the center of the Earth (but, in this
case, within the Earth).  The more complicated problem can be simplified by
modelling the Moon as orbiting around a large, `reduced mass' at the center
of the Earth.  If Snarfy really wants to prove his point, he should calculate
the orbital period of the Moon based upon the reduced mass implicit in his
claimed lunar mass.  [I'd do it here but (a)I have real work to do, and
(b) I believe the figures in my CRC.]

[BTW, one of my pet peeves is people who say "it's", short for "it is", when
they really mean "its", which is the proper form of the singular neuter
possesive pronoun in English.  So there!]
--
Craig DeForest -- astrophysicist for hire.   DoD#314159; PhD#271828

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

Date: 8 Nov 92 23:37:20 GMT
From: Craig Powderkeg DeForest <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.space,alt.conspiracy

In article <foo> [e-mail] (Josh 'K' Hopkins) writes:
   Did you know that fully _half_ of all babies are born within one week of a
   full  Moon!  No kidding.  Of course, if that surprises you or if you take
   allegations of such things seriously, you really could use some help.

Wait!  *I* thought it was that half of all babies were born within one week
of a new moon!  :-)
--
Craig DeForest -- astrophysicist for hire.   DoD#314159; PhD#271828

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

Date: 9 Nov 92 02:54:53 GMT
From: [e-mail]
Subject: NASA Coverup
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Gary Coffman) writes...
>A capture theory requires the influence of a third body, or as you state,
>artificially generated thrust. Both are extremely unlikely. Currently,
>the most popular theory is that the Moon is a result of a collision with
>the primordial Earth by a third body similar in mass to the present day
>Mars. The result of the collision is the much smaller present day Earth
>and the Moon.

Wouldn't a collision with something that size totally destroyed the Earth,
blasting it (and the Mars-sized thing) out of existance leaving not
much more than an asteroid belt?  If not, wouldn't the system be in a
rather elliptical orbit?

Could the Earth have captured the Moon if the Moon was originally a separate
planet in "somewhat the same orbit" as the Vice President would say, and
eventually the Earth-moon perturbed each other into a common orbit?

Also the process that forms binary stars must be common, why not have the
same process form a sort-of binary planet?

I realize the composition of the Moon is evidence against the last 2,
I'm wondering if there more such evidence.

-Mike

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

Date: Mon, 9 Nov 1992 05:31:14 GMT
From: Henry Spencer <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (david michelson) writes:
>>Actually, some of the recent books on Apollo give a reasonably good picture
>>of just how close to the edge that crew came...
>
>I'll bite.  To what recent books do you refer?

Murray and Cox's "Apollo: The Race To The Moon" is pretty good.  It focuses
on Mission Control, but in this context that's reasonable.  Apollo 13 was
the triumph of Mission Control, retrieving the crew from an accident that
was on the very edge of being unsurvivable.  (In fact, had you asked about
it before it happened, the official answer would have been that it *was*
unsurvivable... which is why nobody had planned for it.)

The best account is Henry Cooper's "Thirteen:  The Flight That Failed",
but it's long out of print.

>On a related topic (and it certainly wasn't an option on Apollo 13),
>I vaguely recall that there were some abort options after TLI that didn't
>take the CSM around the moon.  Some mighty hefty burns from the SPS were
>enough to reverse course, so to speak.  Can anyone remember the details?

Murray&Cox mention such "direct aborts" as something that would have been
considered for Apollo 13 had the SM engine still been usable.  I haven't
seen details but I don't think it's anything mysterious.  At very high
altitudes (above the Earth) orbital velocities are low and it doesn't take
that much propulsion to make quite radical orbit changes.

Just had a quick look at Cooper's book; he says there was considerable
interest in a direct abort at first, but apart from doubts about whether
the SM engine could be used, it would have meant jettisoning the LM to
reduce weight, and nobody wanted to do that with the CSM obviously in
deep trouble.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 9 Nov 92 04:51:56 GMT
From: Craig Powderkeg DeForest <[e-mail]>
Subject: NASA Coverup
Newsgroups: alt.conspiracy,sci.space

In article <[e-mail]>, I wrote:
   (the CRC lists Earth's minimum radius
   [the polar one] at 6357 miles, and maximum [equatorial] at 6379 miles),

OOPS -- that should be km, both times.  Should, of course, be clear from
context :-)

--
Craig DeForest -- astrophysicist for hire.   DoD#314159; PhD#271828

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

End of Space Digest Volume 15 : Issue 401
------------------------------