Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V08/V8_302.TXT

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Date: Fri, 29 Jul 88 01:05:39 PDT
From: Ted Anderson <[e-mail]>
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Subject: SPACE Digest V8 #302

SPACE Digest                                      Volume 8 : Issue 302

Today's Topics:
              Re: Rocket engine
             Re: Von Braun quote
              Re: Spy Satellites
             Re: Nuclear Fantasma
              Re: Spy Satellites
              Re: Orbital Launch Methods
          Re: Lithium cells for use on Space Shuttle
               Recent Gender Discussion
              Re: Orbital Launch Methods
            Re: Electromagnetic Launchers
                 Microgravity
               recent gender discussion
            KH-11 Orbital Elements
----------------------------------------------------------------------

Date: 14 Jul 88 15:45:10 GMT
From: vrdxhq!daitc!csed-1![e-mail]  (Jonathan Zweig)
Subject: Re: Rocket engine

Simulating a nuclear EXPLOSION is totally different than simulating a
nuclear BOMB. In the former case you have hot gases, plasma, drag, and
typically at least one axis of symmetry -- in the latter you need
millimeter (or micron) resolution in space, complex systems of wires and
IC's and stuff (Yes! The radio emission from transmissions from the
power leads into your detonator MIGHT MATTER!) to model, probably femto-
second resolution in time, and what your interested in is moving at
relativistic velocities.

I'll eat this VT240 if anybody -- even the big boys at LANL -- is
simulating nuclear bombs going off with intent to circumvent testing. If
you are interested in blast-effects and stuff like that, you can do a
reasonable simulation, but it's fifty orders of magnitude simpler than
taking some CAD information about a bomb and simulating to see if it'll
go off and calculate megatonnage and whatnot.

If any University on the planet has the horsepower to simulate a real
live rocket engine in 3-D taking into account drag, the viscosity of the
propellants, turbulence-effects around all the manifolds and nozzle
effects at every pipe-junction -- the intent being to figure out if a
design works without prototyping it and burning up some test equipment,
then they are keeping very quiet, and I know some DoD and KGB foklks who
might like to have a heart-to-heart chat with them.

(Try simulating a network of 1024 80386-based PC's (a much simpler
problem) and then we'll discuss rocket engines.)

Here's a thought on rocket engine design: fuels rush in where angels
fear to tread.

-Johnny Zweig
(generic
    type NEWSGROUP is limited private;
package DISCLAIMER is
    with TEXT_IO.......;
end DISCLAIMER;)

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

Date: 14 Jul 88 00:02:22 GMT
From: unmvax!charon!geinah.unm.edu![e-mail]  (SEDS-UNM)
Subject: Re: Von Braun quote


Hmmmm.  I wonder if that Phil is really a computer...  Phil <-> Hal ???

Hmmmm.

(just kidding Phil)

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

Date: 15 Jul 88 12:56:26 GMT
From: linus![e-mail]  (Ralph Marshall)
Subject: Re: Spy Satellites

In article <[e-mail]> [e-mail] (Richard the Nerd) writes:
>
>
>Hello space enthusiasts,
>
>There has been some talk on the net lately about spy satellites.  It
>might be of interest to you that our amateur satellite group (based in
>Toronto) has tracked down a few of these.  NASA is not too cooperative
>in this respect since they keep the orbits of these things classified,
>so we find them on our own.  Presently, the best object we are
>-Rich Brezina
> (Kevin Renner, really ;-)
> [e-mail]   (works from most nets)

    I don't know whether or not the orbits are really considered
classified, and I seriously doubt that the Russians don't know where
they are, but if in fact the orbits _ARE_ classified the fact that you
discovered them on your own still does not give you permission to
distribute the information.  It is still classified.

    Personally, I don't much care.  As I said, if you can find them
I'm sure The Other Side can too, so I doubt you're compromising national
security.  I'm merely commenting on the fact that guys from the NSA with
absolutely NO sense of humor might not view it with quite the same
liberal viewpoint, making your venture costly in terms of the harassment
you could get.

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

Date:     Fri, 15 Jul 88 15:45 O
From: <[e-mail]>
Subject:  Re: Nuclear Fantasma

Excuse me for interjecting again my probably outdated rad-lib-pacifist
(since peace is out, war must be in?) worldview into the digest, but I'll keep
it short this time.  It's just that reading the conversation about nuking
the surface of Mars to get rid of inconvenient boulders brings to my mind a
quote from the late Finnish writer and cartoonist Henrik Tikkanen, which I can't
resist quoting:

"Of course we have our problems, but can't they be destroyed,
like everything else?"

Disclaimer: These opinions don't reflect anything; they refract.

Teemu "M-14" Leisti                    U of Helsinki, Dept. of CS
[e-mail]                    Finland

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

Date: 15 Jul 88 14:18:51 GMT
From: agate!garnet![e-mail]  (Obnoxious Math Grad Student)
Subject: Re: Spy Satellites

In article <[e-mail]>, marsh@linus (Ralph Marshall) writes:
>    I don't know whether or not the orbits are really considered
>classified, and I seriously doubt that the Russians don't know where
>they are, but if in fact the orbits _ARE_ classified the fact that you
>discovered them on your own still does not give you permission to
>distribute the information.  It is still classified.

This reminds me of a letter sequence in SCIENCE this past February
or so.  Someone wrote in to complain nastily about some space museum
or other that had been mentioned.  It seems this museum was giving
out these maps/guides to satellites in space, and the complainer was
horrified when he noticed that several TOP SECRET satellites were on
the list.  The person responsible for the maps/guides replied that
when he tried to get satellite information from NASA--innocently
unaware of security problems--he was given some kind of hassle, so
he then wrote to the Soviets for the information, and used that as
his source.

Some of the details may be wrong, but you get the gist.

ucbvax!garnet!weemba    Matthew P Wiener/Brahms Gang/Berkeley CA 94720

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

Date: 15 Jul 88 13:28:18 GMT
From: [e-mail]  (Paul F. Dietz)
Subject: Re: Orbital Launch Methods

In article <[e-mail]> [e-mail] (John Logajan x3118) writes:
>
>I've never worked out the math, but I always wondered if one might be able to
>get into orbit more cheaply by first going straight up and then going
>horizontal at an altitude where the orbital speed would be much lower.
>(I forget, does the moon go 2000mph or 4000mph?)

As I mentioned when talking about electromagnetic launchers, this is
indeed the case, especially if you go into an eccentric rather
than a circular orbit.

Consider an eccentric orbit with perigee distance r1 from the
center of the earth, apogee distance r2.  If v1 and v2 are the
speeds of the spacecraft at perigee and apogee, respectively, then
v1 r1 = v2 r2, by conservation of angular momentum.  So, if r2 / r1 = 20
(say), then v2 < 600 meters per second (since v1 is less than escape
speed).

Depressing the trajectory 30 degrees from vertical increases the
distance through the atmosphere by 15%, but supplies about 1/2 the
needed angular momentum.  The kick at apogee in this case would
be 300 meters per second.

Paul F. Dietz
[e-mail]

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

Date: 15 Jul 88 18:43:33 GMT
From: thumper![e-mail]  (Phil R. Karn)
Subject: Re: Lithium cells for use on Space Shuttle

> >>>The reason NASA bans them from the Shuttle is because they have been
> >>>known to explode when shorted. [...]
>
>    Well, they can explode, or as we preferred to say, "rapidly out-gas",
> but to my knowledge as an eight year design engineer at NASA JSC, they are
> still approved for use.

Okay, the rule is probably applicable only to GAS payloads.

Phil

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

Date: 15 Jul 1988
From: [e-mail]

Date:    Fri, 15 Jul 88       14:01:12 PDT
From:    Donna Reynolds <[e-mail]>
         (University of California, San Francisco)
To:       <[e-mail]>
Subject: Recent Gender Discussion

I am not convinced that this newsgroup is the best possible venue
for a discussion of the pros and cons of "sexist" language.  As the
newsgroup name implies, most sci.space readers (women included) are
here to talk/read about space.  (No flames, please.  I am a woman.)

-DR

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

Date: 15 Jul 88 19:16:55 GMT
From: thumper![e-mail]  (Phil R. Karn)
Subject: Re: Orbital Launch Methods

> I've never worked out the math, but I always wondered if one might be able to
> get into orbit more cheaply by first going straight up and then going
> horizontal at an altitude where the orbital speed would be much lower.

This once occurred to me too, and a friend dubbed it the "tennis ball
serve" launch.

The answer is no. If it weren't for the earth's atmosphere, and if you
could accelerate fast enough, the most efficient launch trajectory into
orbit would be nearly horizontal. Think of a launch as a Hohmann
transfer and it should make sense. Here's another way to think of it:
any thrust component that is directed toward the center of the earth
instead of perpendicular to the vertical is spent merely overcoming
gravity.  Ideally you want all your thrust going into increasing your
tangential velocity.

Real launch trajectories are planned with a complex nonlinear
optimization process that takes into account aerodynamic loads, any
special tracking requirements, and the capabilities (restartability,
throttability) of the various stages. For example, you want to jettison
the fairing as quickly as possible to get rid of its substantial mass,
but you can't do this until the aerodynamic heating is less than some
amount (typically 1Kw/m^2). Doing this quickly requires a more lofted
trajectory, which is less efficient. Launchers typically follow a
preprogrammed flight path for the early part of the flight low in the
atmosphere, and then switch to closed-loop guidance when aerodynamic
forces are no longer a factor.

One aspect of Pegasus that hasn't gotten much comment here is that the
majority of the expected savings in launcher mass come not from the
initial altitude and velocity of the carrier aircraft but rather because
the thinner atmosphere at the launch altitude allows the use of a
flatter trajectory and a less rugged aerodynamical design.

Phil

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

Date: 14 Jul 88 15:48:17 GMT
From: mcvax!unido!ecrcvax![e-mail]  (John Gregor)
Subject: Re: Electromagnetic Launchers

In article <[e-mail]> [e-mail] (Mike Stuard) writes:

> Could a linear electric motor be used?
> If a magnetic track was long enough the extended period of
> acceleration would reduce the G-forces enough for more sensitive equipment
> that is needed in orbit.

You still have the problem of the atmosphere.  It will cause no end of
troubles with heating and drag.

> This idea is much better than the Launch Loop (which is a mechanical
> version of this idea).

If you mean that there is a mechanical link between the payload and the
reaction mass (earth-loop system), you are wrong.  The payload hovers
above and is accelerated by the ribbon via eddy current repulsion.  The
somewhat unique architecture of the loop and the linear motor -> ribbon
-> payload indirection is a result of the need to get things out of the
atmosphere.  But each subsystem is magnetically coupled, not
mechanically.  The only mechanical link is that the linear induction
motors would be rather firmly attached to the planet.  Have you read
the paper?


--

John Gregor                                       [e-mail]

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

Date: 15 Jul 88 20:18:23 GMT
From: [e-mail]  (Paul F. Dietz)
Subject: Microgravity

I am a bit surprised space advocates have not used the following
argument (at least, I haven't seen it):

   Microgravity lets one grow larger protein crystals, so one
   can determine atomic positions using x-ray diffraction with
   better accuracy. (As has been pointed out to me, private
   firms are interested in this for drug design.)

   Knowledge of the precise structure of proteins is necessary
   when designing new proteins, even earth-grown ones.

   The ability to custom design enzymes is the first step to
   nanotechnology.

   Developing nanotechnology will require the ability to debug
   nanomachines, which means determining the position of atoms
   to high accuracy.

So:

   Microgravity will be useful and possibly essential to the
   development of nanotechnology.

Comments?

    Paul F. Dietz
    [e-mail]
    "Our steak prepared to your likeness!"

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

Date: Fri, 15 Jul 88 19:29:36 EDT
From: Marvin Minsky <[e-mail]>
Subject:  recent gender discussion
To: [e-mail], [e-mail]
Cc: [e-mail]

In reply to "k.c. powell": When I was writing "The Society of Mind"
(Simon and Schuster, 1988) I became more and more conscious of the
unconscious gender implications, particularly since the opening
portrays a child building structures with building-blocks.  My own
identification was partly with my own infancy but also partly with
impressions of my first child who happened to be a girl and,
eventually, mathematician and engineer.  The use of "he" irritated me
enough, but I didn't do anything about it until I read (and heard
from) Robin Lakoff.  At first it seemed impossible to write sexually
neutral English but, after what I recollect as a really extensive
skill-acquisition experience, it became second nature.

If you want to see how it can be done, there are examples in virtually
every paragraph.  The trouble is, of course, that you can't see them -
I hope.  In Chapter 3 you'll find traces of some parts I found hard,
and they show a little when I talk about "the child's mind" - instead
of "his/her mind".  And once in a while I tried referring to the child
as "it" - just for fun.  A few parents then complained that I *didn't*
specify the child's sex, and this annoyed them, presumably because
they couldn't invoke a handy stereotype.

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

Date: 15 Jul 88 22:54:38 GMT
From: [e-mail]  (Richard the Nerd)
Subject: KH-11 Orbital Elements


A few of you asked for the Keplerian elements for the KH-11 spy
satellite we have tracked down.  All right, here is our best set.  I
know, I know, this says the perigee is inside the atmosphere, but it
works fine for moderate latitudes.  Can't be perfect all the time!

Satellite: KH-11
Norad: 15423
Epoch: 88189.10268819
Ndot/2: 0
B*: 0
Inclination: 97
RA of Node: 250.4
Eccentricity: 0.038
Arg. of Perigee: 235
Mean Anomaly at Epoch: 125
Mean Motion: 15.765

The drag coefficients were intentionally left at zero since whoever
controls this thing does a very good job of boosting it up (I dunno
where they get all that fuel.)

Last time I saw it (2 days ago) it was 6 minutes early compared to
the prediction.  Expect _big_ errors!  But it's really bright.

-Rich

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

End of SPACE Digest V8 #302
*******************