Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v08/v8_279.txt

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Date: Sun, 17 Jul 88 19:06:29 PDT
From: Ted Anderson <[e-mail]>
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Subject: SPACE Digest V8 #279

SPACE Digest                                      Volume 8 : Issue 279

Today's Topics:
              Space Shuttle Differences
               Re: SPACE Digest V8 #255
            Re: Henry's von Braun comment
     Re: advance space news from June 6 AW&ST -- Pegasus!
             Niven's _Ringworld_
          Re: Long Term Effects of Weightlessness...
     Re: advance space news from June 6 AW&ST -- Pegasus!
               More on Data Compression
               Re: spacecraft computers
                 Re: Pegasus
             Re: Cometesimals at Tunguska
             Re: Cometesimals at Tunguska
----------------------------------------------------------------------

Date: 23 Jun 88 05:22:20 GMT
From: aplcen!jhunix![e-mail]  (Choon Kiat Goh)
Subject: Space Shuttle Differences


 Are all the operational shuttles the same, ie. in terms of lifting
capability, weight, etc. ? Or are there functional differences?

--- Ian ---

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

Date: 23 Jun 88 19:49:26 GMT
From: nsc![e-mail]  (Kchula-Rrit)
Subject: Re: SPACE Digest V8 #255

In article <[e-mail]> [e-mail]
(Dess-DEMON-a) writes:

 > ...

 >Q:  Does anyone REALLY believe that earthings will be able to survive in
 >    space stations in various locations? Just a thought... (Do you think
 >    we'll have an orbital station around Uranus?  Who'd want to live there?
 >    It's SO COLD!)
          ^^^^

    Sure, I'll go!  It'll be just like home!  I'm from Minnesota...

                    K-R

--
                        Kchula-Rrit

"In challenging a kzin, a sream of rage is sufficient.
 You scream and you leap."

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

Date: 23 Jun 88 19:53:26 GMT
From: devvax!jplpro![e-mail]  (Lee Mellinger)
Subject: Re: Henry's von Braun comment

In article <[e-mail]> [e-mail] (Eugene N. Miya) writes:
|
|I don't quite know what Todd meant about Voyager computer problems,
|they added data compression for Uranus and beyond.  There were a few
|other things.  Oh, I did meet Henry last evening at Usenix, briefly,
|associated a net address with a face.
|
|--eugene

Hi Gene, you might remember me from about 1978-79 in regards to a
Modcomp Pascal project I was peripherally involved with in the DSN.

Voyager, which one I don't remember (must be age, the first thing to
go you know), had some serious control problems shortly after launch.
One of the things the project did to clear the problems was a complete
CCDS reload (which the project had promised they would never do).
I remember this quite vividly, as the commanding, 8 plus
hours of it, was done by the then brand new and buggy Mark III command
system at DSS 12.  We were all holding our collective breath.

The Voyager computers have been completely reprogrammed more than
twice since launch, on one occasion to make the attitude control fuel
usage *much* more efficient, and twice to refine the image handling
and compression techniques.

Lee

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
|Lee F. Mellinger                         Jet Propulsion Laboratory - NASA|
|4800 Oak Grove Drive, Pasadena, CA 91109 818/393-0516  FTS 977-0516      |
|-------------------------------------------------------------------------|
|UUCP: {ames!cit-vax,psivax}!elroy!jpl-devvax!jplpro!leem                 |
|ARPA: jplpro!leem!@cit-vax.ARPA -or- [e-mail]            |
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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

Date: 22 Jun 88 17:45:46 GMT
From: hpda!hpcuhb!hpsel1![e-mail]  (Bob Campbell)
Subject: Re: advance space news from June 6 AW&ST -- Pegasus!

>> Man is the best computer we can put aboard a spacecraft. --Von Braun

> . . .
>
> I'd like to see some fighter jock/astronaut do as well by flying a
> launch manually.  Perhaps you should limit the scope of this statement
> somewhat.
>
> Phil
----------

Were all of the computers used onboard the spacecraft?

I agree that Von Brauns statement may need some context help, but we
could quickly disolve into a disscussion of what is a computer.

Bob Campbell                Some times I wish that I could stop you from
[e-mail]        talking, when I hear the silly things you say.
Hewlett Packard                                    - Elvis Costello

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

Date: Fri, 24 Jun 88 04:03:15 EDT
From: "Keith F. Lynch" <[e-mail]>
Subject: Niven's _Ringworld_
To: [e-mail]
Cc: [e-mail], [e-mail], [e-mail],
        [e-mail]

There are no major problems with the concept of a ringworld.  Obviously
it would be an extremely difficult engineering feat.  There are several
minor problems, most of which Niven addresses in his sequel _The
Rignworld Engineers_.

Personally, I think it would be more likely that people will colonize
asteroids, and when we run out that we will demolish useless planets to
make more asteroids.  Ultimately, this strategy can support a much
higher population than a ringworld.  It's also much more immune to
common-mode failures such as the superconductor eating bacterium in
_Ringworld_ and the far greater danger in _The Ringworld Engineers_.

                                ...Keith

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

Date: 23 Jun 88 22:58:53 GMT
From: ihnp4!ihlpm![e-mail]  (DiMasi)
Subject: Re: Long Term Effects of Weightlessness...

Scott S. Campbell writes:
>
> .....
>
> I'm generally (i.e., non-techinically) curious about the affects of
> weightlessness on the human body over long periods of time.  Now that the
> Soviet Union has put several people into zero-G for extended periods of time,
> has there been any mention of the ability of these cosmonauts to re-adapt to
> the pull of Earth's gravity?  How did the recovery time relate to the amount
> of time spent in the space station?  What thereapy was necessary to re-adjust?

I don't recall the details, but I remember reading (about 2 years or so ago?)
that cosmonauts who had flown on more than one long-duration mission re-adapted
to 1G more quickly on their second (third if any) missions.  It seems that
the human body "learns" to re-adapt.  As I remember, only re-adaptation to
1G in terms of ability to move around easily, pick up objects, etc. was
discussed in the article I read.  I don't recall anything about recovery of
muscle mass, bone mass, etc.

Nick DiMasi
Uni'q Digital Technologies (Fox Valley Software subsidiary;
   ^          working as a contractor at AT&T Bell Labs in Naperville, IL)
(  | this is an accent mark, supposed to replace the dot over the 'i')

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

Date: 24 Jun 88 01:14:36 GMT
From: necntc!adelie!infinet![e-mail]  (Rob Horn)
Subject: Re: advance space news from June 6 AW&ST -- Pegasus!

In article <[e-mail]> [e-mail] (Roy Smith) writes:
>[e-mail] (Henry Spencer) writes:
>> Pegasus, a winged three-stage design that will be air-launched from a B-52.
>> [...] Payload is 600lb into low polar orbit, 900 into low equatorial orbit.
>
>What does a typical commsat weigh, for example?
Depends on the type.  Geosynch tend to be heavier.  2000kg and up.
One major consideration is power supply and another is fuel for
station keeping.  BUT, low earth orbit fit easily in this.  The latest
AMSAT (Up and WORKING !!!! yeah) weights 140 kg.  This kind of
satellite supports packet radio techniques.  DARPA has funded paper
studies of a ``cloud'' of these as an alternative to geosynch.

>  Or a typical package of
>scientific instrumentation?
I've gotten data from a 10kg satellite.  But there is no typical.
>  Or (God forbid), a typical military payload
>(warhead, spysat, whatever).
Spysats are HUGE, partly because optics are huge and partly because
they want maneuvering capability (fuel+motor) and partly for long
life.  But a lot of this is the result of the present difficulty in
making a decision to launch on a day's notice.  (Optics being the exception.)

--
                Rob  Horn
    UUCP:    ...harvard!adelie!infinet!rhorn
        ...ulowell!infinet!rhorn, ..decvax!infinet!rhorn
    Snail:    Infinet,  40 High St., North Andover, MA

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

Date: Fri, 24 Jun 88 14:05:48 PDT
From: Eugene Miya <[e-mail]>
To: [e-mail], [e-mail]
Subject: More on Data Compression

Just when you thought it was safe to go back and read Aviation Leak and
Space Technocracy, the latest issue of Computing Surveys has an article
on DATA COMPRESSION.  It's not a bad article by two authors from Irvine,
it lacks a few words (I think the section on Errors could say a bit more,
but it is a Survey).

%V 19
%N 3
%D Sept. 1987

I decided to give the above refer with keywords (The list is more than I want
to type).
%P 261-296


--eugene

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

Date: Fri, 24 Jun 88 16:24:37 EDT
From: [e-mail] (Paul F. Dietz)

Interested parties might want to read this article:

  "Electromagnetic Launch: Highway to the Stars", IEEE Trans. on
  Magnetics, Vol. 24, No. 2, March 1988, pages 703-710.

It is highly readable, if somewhat hyperbolic, and makes some
interesting claims.  To summarize...

Use of space has been blocked by the stagnation of launch cost
using chemical rockets.  Historically, further progress depends on
the introduction of new technology. Electromagnetic launchers promise
much higher payload ratios.  Recent progress in e.m. launcher and
associated technology has been rapid.

The article describes one particularly attractive concept, called
the solenoid quench gun.  The launcher is a superconducting solenoid
with a field of 20-30 Tesla.  The projectile coil, also
superconducting, is accelerated up the solenoid, quenching
solenoid segments as its goes (so the coil remains at the "end"
of the solenoid).  If the quenched coils are shunted through a
s.c. circuit the efficiency can approach 100%.

The most interesting things about the launcher are its inherent
simplicity and small size.  The article claims that a 3 ton projectile
(1 ton of which is payload destined for geosynchronous orbit) could
be launched by a gun with a mass in the *tens* of tons.

E.m. launchers would seem to be well suited to materials processing,
since only a modest kick motor is needed to raise the projectile into
a long elliptical orbit (and, similarly, to deorbit it).

    Paul F. Dietz
    [e-mail]

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

Date: 24 Jun 88 20:31:32 GMT
From: pioneer![e-mail]  (Eugene N. Miya)
Subject: Re: spacecraft computers

In addition to the well cited CACM articles, I recall the IEEE has advertised
some books on spacecraft computer systems.  I seem to recall them
because I think they were advertised with some books on communication
systems by Pierce and Posner.  Serious readers can determine this (costs
were in excess of $75, I'll check Posner next time I swing past my old
Branch's library).  Computers onboard tend to be small, small scale
things.  I think Lee would agree with this. 8-)  I think most of the
companies who would seriously buy these books will not be on the net
(like Hughes or Huge).  I also note there is increasing interest in GaAs.

Another gross generalization from

--eugene miya, NASA Ames Research Center, [e-mail]
  resident cynic at the Rock of Ages Home for Retired Hackers:
  "Mailers?! HA!", "If my mail does not reach you, please accept my apology."
  {uunet,hplabs,ncar,decwrl,allegra,tektronix}!ames!aurora!eugene
  "Send mail, avoid follow-ups.  If enough, I'll summarize."

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

Date: 22 Jun 88 15:27:35 GMT
From: mnetor!utzoo!dciem!nrcaer!cognos!geovision![e-mail]  (Alastair Mayer)
Subject: Re: Pegasus


Don't have the reference handy to give the exact figures, but Pacific
American's  Liberty I launcher has equivalent payloads to Pegasus to
orbit at around $2 to $4million.  Payload weight may even be higher.
Either way the per/lb cost is substantially less than Pegasus.
  And yes, Pacific American has a customer for Liberty I, they're
currently bending metal on it.  (I heard they're 'rolling out' first
engine and propellant tanks this week or next).
  Liberty is conservative design: pressure-fed LOX/kerosene first stage,
N2O4-hydrazine second stage.  That's one of the keys to low cost.

--
 Alastair JW Mayer     BIX: al
                      UUCP: ...!utzoo!dciem!nrcaer!cognos!geovision!alastair

"Anyone who is not shocked by quantum theory has not understood it."

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

Date: 24 Jun 88 15:18:49 GMT
From: hplabsb![e-mail]  (David Smith)
Subject: Re: Cometesimals at Tunguska

In article <[e-mail]>, [e-mail] writes:
>            In 1908, a large explosion flatened a section of the Tunguska
> region in Siberia. As far as I know, there has never been a satisfactory
> explaination for this event.
>
> The sticking point is that the damage pattern matches that of a nuclear air
> burst. Trees are broken down in a pattern radiating away from ground zero,
> but with no significant crater or extra damage at ground zero itself. This
> couldn't happen with a normal meteor, because anything large enough to have
> caused the blast would have survived to ground impact.
>
> I wonder if the fluffy snowball wouldn't do it. I'm thinking that a large,
> low density, fast moving object could couple all of its kinetic energy to
> the atmosphere. This would leave a shock wave traveling on the same path as
> the object, which might leave the right damage pattern.

Around six years ago, Science News ran an article on explosions of
meteors, largely based on photographic patrols in Czechoslovakia.
The conclusion was that fast-moving stony meteors, undergoing great
stress in the atmosphere, can suddenly shatter into many small pieces.
The greatly increased surface area causes extremely rapid "burn-up" of
the fragments in an explosion.  The researchers believed this to be the
best explanation of the Tunguska event.
--

            David Smith
            HP Labs
            [e-mail]

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

Date: 25 Jun 88 21:18:25 GMT
From: puff![e-mail]  (Lou Goodman)
Subject: Re: Cometesimals at Tunguska


when speaking of "old" sources for Tunguska, I seem to remember
one of the films in the ACClarke "mysterious somthing-or-other"
in which he examined it. One of the experiments made was to do
an air blast over simulated trees. The zone of "ground zero" under
the simulated blast was relatively unaffected by the blast while
outside of that zone the "trees" were flattened.

He also pointed out that it was not until the 20's that anyone
even got to the site and that it is a morass of fens and bogs,
very people unfriendly. I've always enjoyed the "spaceship
(read ufo) gone critical". By now most evidence (if any does
or did indeed exist) may be gone/incorporated into the current
matrix.


astrix (Lou R. Goodman), UW Madison

-------------------------------------------------------------------
|| He who knows, who really knows, and knows that he knows...... ||
|| knows just how much he doesn't know......                     ||
-------------------------------------------------------------------
|| "Sticks and stones can break my bones, but flames... oy weh!" ||
-------------------------------------------------------------------

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

End of SPACE Digest V8 #279
*******************