Date: Mon, 5 Sep 88 19:04:53 PDT
From: Ted Anderson <ota@angband.s1.gov>
Message-Id: <8809060204.AA01144@angband.s1.gov>
To: Space+@andrew.cmu.edu
Reply-To: Space+@andrew.cmu.edu
Subject: SPACE Digest V8 #350

SPACE Digest                                      Volume 8 : Issue 350

Today's Topics:
		     Initials for the Uninitiated
			Orbital Mech Algorithm
		       Interstellar Mining (?)
		   RE space expoitation/exploration
TRW selected to develop Advanced X-ray Astrophysics Facility (Forwarded)
	     Re: Why *THEY* might want to eat our lunch.
		  Re: space news from July 11 AW&ST
		Re: SETI: Why don't we hear anything?
		 RE:  space exploitation/exploration
----------------------------------------------------------------------

Date: 23 Aug 88 07:53:06 GMT
From: amdahl!nsc!taux01!taux02!amos@ames.arc.nasa.gov  (Amos Shapir)
Subject: Initials for the Uninitiated

Would it  be too  much to  ask of posters  in this  group not  to assume
everybody understands the  initials they use? I guess  most readers know
what NASA or SDI mean, and in this  group it's pretty safe to use ESA or
USAF, but I'm sure many readers are bewildered by AXAF, FRF, AW&ST, NRC,
OMV,  SRB, RCS  or SSME,  to quote  just a  few used  in the  referenced
article.

No, don't rush to post or mail  me explanations of these, I have already
taken the trouble to look them up;  all I ask is that future posters use
the  full  text of  the  initials,  at least  the  first  time they  are
mentioned.
-- 
	Amos Shapir				amos@nsc.com
National Semiconductor (Israel)
6 Maskit st. P.O.B. 3007, Herzlia 46104, Israel  Tel. +972 52 522261
34 48 E / 32 10 N			(My other cpu is a NS32532)

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

Date:    Tue, 23 Aug 88 10:09:23 PDT
From: greer%23666%utadnx%utspan.span@vlsi.jpl.nasa.gov
Subject: Orbital Mech Algorithm
X-St-Vmsmail-To: JPLLSI::"SPACE@angband.s1.gov"


Re: Orbital Mechanics questions asked by Munck, answered by Mueller
 
>I'd like to call on the combined expertise of the net for something I've
>been unable to find;  it's entirely on a "hobby" basis, no connection
>with anything commercial.
> 
>I want a simple, fast subroutine that will compute orbital motions...

>>You are attacking a non-trivial problem.
 

The triviality of a mathematical task depends on the accuracy desired and the
compute power available. 

	A general orbital mech algorithm can be very simple, e.g.:

		Do
		  a = -G*M*r/|r|**3
	          v = v0 + a*dt
		  r = r0 + v*dt + 0.5*a*dt**2
		Loop

	Where r, v, and a are vectors, G is the gravitational constant, and M
is the mass of the body being orbited.  This algorithm may not do well to
figure when MIR will next be overhead, but it's good enough to give a feel for
orbital mechanics.  More stuff can be added to the acceleration: 

	a = -G*M1*r1/|r1|**3 - G*M2*r2/|r2|**3 - ...
            + thrust + any_other_acceleration

	The accuracy, for *spherically symmetrical* bodies, depends on the ratio
v*dt:rM, since the algorithm assumes the acceleration is constant over the
period dt.  In a highly eccentric orbit, for example, the inaccuracy will be
greater near the periapsid than near the apoapsid.  Interestingly, this effect
is completely conservative over the period of an orbit, since the errors on one
one half of the orbit negate the errors on the other half.  The orbit keeps its
shape but precesses at a rate dependent on the ratio v*dt:r_periapsid. 
	Oops! I guess that means it isn't *completely* conservative if there is
precession, but the semi-major axis stays the same, even if the line of apsides
moves around.
	The algorithm is plenty fast enough to do an engaging and enlightening
simulation on the Mac, i.e., Orbital Mech (TM), even without the use of the
floating point unit of the Mac II.  I wrote Orbital Mech to run on any Mac, and
had to assume no FPU would be available.  I think you could do a pretty hot
orbital simulator with an 80386 and FPU.

"I feel like somebody strapped a		|       Dale M. Greer
 couple of jet engines on my back		| Center for Space Sciences,
 and we're ready to take off!"			|       UT at Dallas
                 -- Pat Robertson

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

Date: 23 Aug 88 17:04:25 GMT
From: cfa!cfa250!willner@husc6.harvard.edu  (Steve Willner P-316 x57123)
Subject: Interstellar Mining (?)

From article <3695@drivax.UUCP>, by macleod@drivax.UUCP (MacLeod):
> Given the unlikelihood of cheap transmutation of elements, even spacefaring
> races will probably continue to be interested in rare elements.  If Earth's
> crust is abnormally rich in these, we may be in for interesting times ahead.

Transmutation of elements typically takes about 0.1% of the rest mass
energy.  This amount of energy corresponds to a speed of about 3% of
light or about a 100 year trip to alpha Cen.  (Note: Piddly factors
of 2 and such are ignored.  The calculation implicitly assumes that
the mass of the interstellar vessel is mostly payload.)  The
energetics thus suggest that interstellar travel and element
transmutation are about equally difficult.

Speculating on the economics of advanced societies is a dubious
proposition, but it seems to me that transmutation would be
economically more attractive because of the shorter payback period
and thus the lower cost of capital equipment.  In fact, I would turn
the argument around and say that any interstellar-travelling society
is likely to use element transmutation routinely.

-- 
Steve Willner            Phone 617-495-7123         Bitnet:   willner@cfa
60 Garden St.            FTS:      830-7123           UUCP:   willner@cfa
Cambridge, MA 02138 USA                 Internet: willner@cfa.harvard.edu

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

Date: 23 Aug 88 15:18:00 GMT
From: apollo!nelson_p@eddie.mit.edu  (Peter Nelson)
Subject: RE space expoitation/exploration


> **********WARNING: NEW KID ON THE BLOCK WITH A CHIP ON HIS SHOULDER********
 
> Space is not some natural resource which can or should be controlled by an
> governmental or extra-governmental entity.  Instead, it is a resource much
 [ ... ] 
 
> Why?  Mankind needs room, we need to get off each other's shoulders. The
> sooner we spread out in this system (and beyond, but that happens MUCH
> later) the sooner we, as a race, can start believing that we might survive
> our own stupidity.  There's plenty of room out there for Palestine or
> Armenia or even White South Africa.  And something for the misfits in our
> society who would have been trappers and explorers and miners in a previous
> era.

  Sure if you don't mind living in lo-grav, crowded quarters and never
  going to the beach.  I don't know what you mean by 'room' but unless
  you like living in a pressure suit you're going to be living 'indoors'
  all the time.  Sounds cramped to me.  Besides you miss the entire point 
  of what the Palestinians, white South Africans, et al, want.
        
  Currently the world's population is growing at about 75 million
  people a year.  Even if we could slow our population growth to 50
  million a year, we'd have to ship a million people a week into space
  just to break even.  It's not like shipping colonists to the New World.
  The shelter, food, and life-support systems for them would have to be
  waiting when they arrived.

> Basically, though, none of this will happen if some Mickey Mouse (sorry
> Walt) third world country claims co-soveriegnty by virtue of some "natural
> right to share".  On the other hand, if I'm up there (and I plan to be),
> then any one who disputes me is welcome to come up with me.

  What do you mean by 'plan' to be?  My wife and I plan to take a
  vacation soon in Australia.  I've charted out my route, made
  airline arrangements, computed costs, determined how long I can stay, etc.
  What does your 'plan' consist of?   What have you *actually done* to
  further your plan?  

  One of the (many) reasons why our space program is going nowhere fast
  is that we have too many romantic dreamers who spend their time reading
  Omni and watching reruns of Star Trek and too few pragmatists.  Do you
  have any idea what it costs to even put a *handful* of people into 
  space for a few days and keep them there safely?  Do you have any concept
  of what would be required to create even a *small* self-sustaining colony
  of even a few hundred people?  Lots and lots of money and an enormous
  technological, industrial and academic base.  Do you really think they're 
  going to waste those resources and training putting 'misfits' up there?

                                              --Peter Nelson
 
> Dillon Pyron

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

Date: 23 Aug 88 22:16:05 GMT
From: yee@ames.arc.nasa.gov  (Peter E. Yee)
Subject: TRW selected to develop Advanced X-ray Astrophysics Facility (Forwarded)

Charles Redmond                                August 22, 1988
Headquarters, Washington, D.C.                 4:00 p.m. EDT

Bob Lessels
Marshall Space Flight Center, Huntsville, Ala.


RELEASE:  88-118

TRW SELECTED TO DEVELOP ADVANCED X-RAY ASTROPHYSICS FACILITY


     NASA announced today that TRW, Inc., has been selected for 
final negotiations leading to the award of contracts for extended 
definition and development of the space-based Advanced X-ray 
Astrophysics Facility (AXAF).

     The development contract will include a mirror development 
phase and a priced-option for spacecraft development and 
completion of the observatory.  Exercise of the option by NASA 
will require congressional approval and will be based upon the 
successful fabrication of the largest of six mirror pairs to the 
required resolution.  The principal place of performance will be 
the TRW plant, Redondo Beach, Calif., and that of the major 
subcontractor, Kodak Federal Systems Division, Rochester, New 
York.  The proposed cost of the contracts is approximately $508 
million.

     The facility will be the third in NASA's series of space-
based great observatories, following the Hubble Space Telescope 
and the Gamma Ray Observatory, into orbit in the mid-1990's. 
These observatories, as well as the Space Infrared Telescope 
Facility, which is to follow the X-ray observatory, will permit 
simultaneous, complementary observations of astrophysical 
phenomena over different wavelengths of the spectrum.

     The objective of this project is to develop a high-quality, 
X-ray telescope to be used by the international scientific 
community in conjunction with NASA for an operational period of 
15 years. 

     The observatory will be designed for on-orbit maintenance in 
order to extend its life and to upgrade its scientific 
capability.  The X-ray telescope will be used to gather data to 
expand our knowledge of quasars, black holes and the geometry and 
mass of the universe.

     The Marshall Space Flight Center, Huntsville, Ala., has 
management responsibility for the telescope and will manage the 
contract.  The AXAF program is under the direction of NASA's 
Office of Space Science and Applications, Washington, D.C.

     Also proposing was Lockheed Missiles and Space, Co., 
Sunnyvale, Calif.

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

Date: 23 Aug 88 22:38:24 GMT
From: tektronix!teklds!mrloog!dant@ucbvax.berkeley.edu  (Dan Tilque;1893;92-101;)
Subject: Re: Why *THEY* might want to eat our lunch.

Michael MacLeod writes:
>The last I heard (in lay articles) there were several theories that best
>seemed to fit observed facts about the genesis of the Moon and Earth planetary
>pair.  One of these called for a collision between the Earth and another
>body, carving out the Moon as a result.   This also explained the abundance
>of heavy elements near the top of the Earth's crust.  In Sunday supplement
>fashion, one article brayed: "The Gold In Your Ring is From Another Planet!"

The gold in your ring probably owes more to hydrologic and biologic action
than it does to a collision 4 billion years ago.

>If this is so, and such metal dispositions are rare in the universe (perhaps
>most planets turn out to be Jupiter-size gas giants), then any kind of mining
>survey is going to be of interest to those looking for accessible heavy
>elements.  

1) There are 5 terrestrial (rocky) type planets (Mercury, Venus, Earth,
Moon and Mars) in our solar system.  Relative to the gaseous and icy
planets in the outer solar system, these all have a high percentage of
metals (probably including heavy ones) in their crusts.  There are also
thousands of asteroids for which the same is also true.

2) The rocky nature of the inner solar system bodies is not an
accident.  It's probably safe to assume that many (if not most) single
stars and some double star systems have many rocky bodies in their
inner planetary system.

3) While veins of heavy metals are not likely on the other terrestrial
planets (no biological or hydrologic action), it's still possible to mine
them if you're given sufficient energy.

4) Iron and stoney-iron asteroids have many of their metals differentiated
out (probably at least as well as many veins of ores).

>Given the unlikelihood of cheap transmutation of elements, even spacefaring
>races will probably continue to be interested in rare elements.  If Earth's
>crust is abnormally rich in these, we may be in for interesting times ahead.

Seems to me that it would take a lot more energy to travel several
light-years than to take an asteroid apart for its materials.


---
Dan Tilque	--	dant@twaddl.LA.TEK.COM

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

Date: 23 Aug 88 16:39:04 GMT
From: attcan!utzoo!henry@uunet.uu.net  (Henry Spencer)
Subject: Re: space news from July 11 AW&ST

In article <880822121249.000001030E1@grouch.JPL.NASA.GOV> PJS@grouch.jpl.nasa.GOV (Peter Scott) writes:
>I seem to remember that one of the problems with ICBMs (also solid-fuelled)
>is that they have a finite and relatively short `shelf' life due to the
>propellant...  These SRBs are at least 2 years old,
>isn't this problem likely to be a consideration?  Unmanned or not, we can't
>exactly afford to lose the Columbia...

Yes, solid fuels do have a limited shelf life; this is one reason why the
USAF can justify a steady stream of Minuteman test launches from Vandenberg,
since the missiles won't last forever anyway.  But two years isn't enough
to make anyone really worry much.

And yes, rationally speaking, the unmanned nature of the proposed flights
is almost irrelevant, since the orbiters are a lot harder to replace than
the crews.
-- 
Intel CPUs are not defective,  |     Henry Spencer at U of Toronto Zoology
they just act that way.        | uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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

Date: 22 Aug 88 20:38:11 GMT
From: ndsuvax!nekinsel@uunet.uu.net  (Peter Kinsella)
Subject: Re: SETI: Why don't we hear anything?

In article <4989@watdcsu.waterloo.edu>, smann@watdcsu.waterloo.edu (Shannon Mann - I.S.er) writes:
> In article <561@unisv.UUCP> vanpelt@unisv.UUCP (Mike Van Pelt) writes:
> - large chunk left out to conserve bandwidth -
> Furthermore, as the radiosphere expands, the
> transmissions become more and more weak, disrupted by background noise, etc.
> Although the calculation is beyond me, I believe that, after a certain distance,
> the signals would be so weak as to become part of the background noise.
   
     I don't suppose background noise could actually be transmissions
 from various developed cultures ?   any comments ?

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

Date: 24 Aug 88 14:43:00 GMT
From: apollo!nelson_p@eddie.mit.edu  (Peter Nelson)
Subject: RE:  space exploitation/exploration


 In the mailbag today another dreamer writes...

>By room, those of us who believe in space and would invest in space mean room
>for mankind to thrive with independent societies.  This is becoming impossible
>on earth, with the spread of the welfare state, etc.  We do not want these
>statists to do anything more than get out of the way so man can live in space
>as free people.
 
 I might point out that the society today with with the most advanced space 
 program is also the the most 'statist' society on Earth: the USSR.

 Talk is cheap (except maybe on Usenet).  Results are what count.  The 
 U.S. has not had a space program to speak of for over 2 1/2 years and
 it isn't clear how much of one we're going to have in the future.  Yet
 I haven't seen private industry clamoring to provide an alternative.

>The greatest immorality of all is to impose ones morality on others.

  You don't say? . I thought it was torturing babies but let's not
  quibble over details...

>   We need independent societies in space; you would impose your
> standards, while I say only that if you do not wish to support me,
> do not hinder me.

  Where have I offered to impose my standards???   All I said to the 
  other guy, and I'll say it to you too, is:  What have you *actually 
  done* to further this dream of yours of going into space to start a 
  new society?  You're talking about a project that would absolutely
  dwarf any previous engineering or technical achievement in cost and
  scale!  If you want something like that to happen in your lifetime you
  had better be working real hard on it now.
 
  BTW, I'm actually very fond of dreamers and eccentrics, as I am sometimes
  one myself ;-)   America has a rich tradition of utopianism and there is
  an excellent book on the subject by Dover Press called 'Heavens on Earth'
  (by Mark Hollowell, I believe).  But one thing to remember is that there
  have been hundreds (if not thousands) of utopian communities started 
  with grand visions of how their particular philosophy would transform
  life and attract millions of followers.   Most of them fizzled within
  a year or so and even those that lasted for many years ultimately 
  either died out or adopted mainstream values and lifestyles.  This 
  notion that 'if only we could create a society of like-minded individuals
  we could all be free/happy/whatever has NEVER panned out.  And by the
  way, to my Libertarian friends: Historically, the most successful of
  the utopian experiments have, by far, been those which adopted 
  communist (NOTE THE SMALL 'c'!!) principles rather that individualist
  ones.  
                                       --Peter Nelson

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

End of SPACE Digest V8 #350
*******************