Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_6/V13_697.TXT

Internet Message Format | 1991-06-24 | 19KB

Return-path: <[e-mail]>
X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson
Received: from hogtown.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/[e-mail] (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests)
          ID </afs/andrew.cmu.edu/usr1/ota/Mailbox/kcNNmxm00WBw48GU5t>;
          Mon, 24 Jun 91 03:18:21 -0400 (EDT)
Message-ID: <[e-mail]>
Precedence: junk
Reply-To: [e-mail]
From: [e-mail]
To: [e-mail]
Date: Mon, 24 Jun 91 03:18:16 -0400 (EDT)
Subject: SPACE Digest V13 #697

SPACE Digest                                     Volume 13 : Issue 697

Today's Topics:
            Re: Beanstalk analysis reprise
     Re: L-5 Society is now National Space Society (NSS)
            Re: Fred Vote Thursday
       Pendulum analogy for sloshing propellants - help needed
         Re: Self-sustaining infrastructures
      Lunar gravity in movies, was Re: Moonbase movie *Plymouth*
          NASA Prediction Bulletins:  Space Shuttle
              Re: Microgravity?
            Re: RFD:  talk.politics.space
               Re: More on Freedom Vote

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription requests,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

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

Date: 5 Jun 91 20:57:46 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!caen!ox.com!fmsrl7![e-mail]  (Ron Carter)
Subject: Re: Beanstalk analysis reprise

In <[e-mail]>,
 [e-mail] (Walter Dnes) writes:
>     I get to play the devil's advocate again.

I wish you'd find something you do well, and then do it.

>I don't like to
>destroy people's dreams, but a reality check is in order here.

Don't flatter yourself.

>Your calculations seem to be based on an airless earth, i.e a
>good vacuum. Don't forget that we have an atmosphere.

Beanstalks don't do work on the air, so air drag is not a
major consideration.

>     1) You've allowed for longitudinal forces. What about
>perpendicular forces ? What happens when the beanstalk gets hit
>by a 100 km/h (60 mph) wind ? How about a 250 km/h

If the wind continues long enough, the beanstalk assumes a
catenary curve rather than running upward in a straight line.
Changing winds excite vibrations, which may have to be damped.

Alternative:  trifurcate the beanstalk at a point high in
the stratosphere.  Attach each third to a separate anchor,
on the points of an equilateral triangle.  No matter which
way the wind blows, it only moves tension from one part
to another; it does not push the beanstalk as a whole.

>Can you supply some typical "Asurf" values...

Depends how much you want to lift.  1 square inch @ 2MPSI
working tension should be able to lift 100 Klbs.  The weight
to be lifted is not something which can be determined a priori.

> along with the taper as a function of height.

I posted all the mathematics required to do that.  Evaluate
the taper integral for some endpoint other than geosync.
I assume you still want the bottom to be on terra firma,
so the 6380 km lower limit for the integration stands.

You lose two points for not having the wits to know the
answer was in your hand.

>     2) Since a geosynchronous orbit sits on the equator, you
>won't have to worry about icing... *AT SEA LEVEL*. At higher
>elevations in the atmosphere it will be a worry in two ways.
>Heavy icing will strain the beanstalk by sheer weight alone.
>Icing will also increase the cross-section that wind loading
>works on.

Any flex in the beanstalk, or vehicles moving up and down,
will cause it to shed ice.  Also, it can be heated electrically
if icing is a difficulty.

>     3) Surface temperatures at the equator can hit 40C to 50C.
>You can expect -40C to -50C up in the atmosphere, and some
>utterly farcical values (both hot and cold) in the vacuum of
>space. How will your materials react to this gradient ? How will
>the outer-space portion of the beanstalk react to extreme diurnal
>cycles (day/night) in a vacuum ?

You are trying to tell me that a 100 C temperature difference
between two parts of a very narrow structure some kilometers
distant is going to cause problems with differential expansion?
<<Ron rolls on the floor laughing>>

Graphite, aluminum, Mylar, and many other materials have no
problems whatsoever with the "extreme diurnal cycles".

>     4) Besides a beanstalk, you'll also be operating the world's
>biggest damn lightning rod. What happens to the crystalline
>structure of the beanstalk after a few hits ? I'm assuming, of
>course, that the beanstalk isn't so thin at low levels that the
>first good strike evaporates several meters of the beanstalk.

If its resistance is high enough to make heating from lightning
strikes a problem, coat it with aluminum or something else
highly conductive.  Currents to ground can be limited by
insulating the bottom end of the beanstalk and grounding it
through a high-impedance leak, which will absorb the bulk of
the energy of any current flow.  End of problem.

A much greater difficulty will be supporting the required
weight of aircraft warning strobes and such.  It may make
more sense to use a Lofstrom loop for the portion of the
structure which is in the atmosphere, because it can be
self-supporting and carry (and power) lots of accessories.
The tension-supported part could run from 80 km upward.
(This also cuts the required amount of material for the
rest of the tether by about 1/e; quite a savings!)

>     5) What about charged particles in the van Allen belts
>"doping" the crystalline structure of the beanstalk ?

Replace weakened strands as they lose strength, or creep lengthens
them beyond the maximum length for good strands.  If doping doesn't
cause weakening or embrittlement, then it is irrelevant.

I'm disappointed that you can't come up with better objections.
Much more to the point would be "Where are you going to get 15
million metric tons of graphite whisker?"  That's a much more
difficult question, because we don't know how to make the stuff
in quantity yet.  I'm assuming that this will be done, soon,
because the market for high-strength fibers is large and
growing, and the state of the art is progressing rapidly.

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

Date: 6 Jun 91 01:30:11 GMT
From: agate!spool.mu.edu!rex!wuarchive!usc!isi.edu![e-mail]  (Craig E. Ward)
Subject: Re: L-5 Society is now National Space Society (NSS)

In article <[e-mail]> [e-mail] (James T. Green) writes:
>In article <[e-mail]> [e-mail] (W.A.Simon) writes:
>>    does anyone know what has the L5 Society become?  I have
>>    not hear of/from/about them in years.
>>
>The L-5 Society merged with the National Space Institute
>several years ago.  The new organization is called
>the National Space Society and is headquartered in
>Washington DC, with about 100 chapters last time I
>checked.

There are over 130 chapters now, covering North America, Europe, Asia, and
Australia.  (The list I have now doesn't have the Ecuador chapter.  If it's
still alive, add South America.)  Australia is also organized nationally.
The most recent chapter is a SIG covering the uses of nanotechnology.

For more information, write (if you're in California, write me):

National Space Society            National Space Society of Australia
922 Pennsylvania Ave. SE        5 Boyce Ave.
Washington, DC 20003            Homebush, NSW 2140 Australia
[phone]                [phone]

The NSS Family of Organizations includes a lobbying group, Spacecause, and a
Political Action Committee, Spacepac.  These can also be reached the DC
address.  (Australia also has a Spacecause.)

NSS offers a variety of ways to get involved and make a difference in
creating "a spacefaring civilization with communities beyond the Earth."
--
Craig E. Ward <[e-mail]>     Slogan:    "nemo me impune lacessit"
USPS:    USC/Information Sciences Institute
    4676 Admiralty Way, Suite 1200
    Marina del Rey, CA 90292

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

Date: 5 Jun 91 07:17:12 GMT
From: agate!spool.mu.edu!rex!wuarchive!emory!wa4mei!ke4zv![e-mail]  (Gary Coffman)
Subject: Re: Fred Vote Thursday

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>This is incorrect, 217 is enough to win by one vote. At the moment there
>are only 432 members in the House (three seats are vacant due to death,
>resignation, ect). Also note that a tie is a win since the VP gets the
>tiebreaking vote.

The VP is President Pro Tem of the Senate, not the House.

Gary

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

Date: 5 Jun 91 16:05:36 GMT
From: eagle!venus.lerc.nasa.gov![e-mail]  (Ronald E. Graham)
Subject: Pendulum analogy for sloshing propellants - help needed

I have an application involving the dynamics of a spinning spacecraft
(in this case ACTS) undergoing thrust from low- to high-earth orbit.
The question concerns energy dissipation during the maneuver caused by
sloshing of propellants.

I have created a simple math model to describe the dynamics of this
system, and I am modeling the sloshing propellants as pendulums.  Each
pendulum has two degrees of freedom (one responding to thrust, the other
to spin transients), and has time-varying mass and length (due to the
depletion of propellants).  If the spacecraft is assumed to have no
center-of-gravity offset of thrust misalignment, and if each propellant
tank is depleted at the same rate, then all pendulum DOFs can be treated
as having the same response.

What I am looking for are references that describe the means of selecting
pendulum mass and length, given shape of tank, percentage full, and flight
conditions.  There has been work done for launch vehicles by the folks at
the Southwest Research Institute, but I would like, if possible, to hone
down the literature search before it begins.  Can anyone help me locate
some info on this subject?  I would be most grateful, and would be glad to
summarize if I get more than one relevant response.

Follow-ups directed to sci.engr, due to the technical nature of the subject.

RG

"talk.politics.space" - its time has come.

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

Date: 5 Jun 91 21:09:37 GMT
From: iggy.GW.Vitalink.COM!widener!hela![e-mail]  (Allen W. Sherzer)
Subject: Re: Self-sustaining infrastructures

In article <[e-mail]> [e-mail] (Henry Spencer) writes:

>Titan IVs, while not in abundant supply, are available to NASA if it asks
>far enough in advance and coughs up the cash.

In fact the Air Force recently reduced the number of Titan IV's they
will buy per year. This means that Martin likely can make more if
needed. Also, Titan III is made on the same line and there is no
trouble making them. Production shouldn't be a problem.

   Allen

--
+---------------------------------------------------------------------------+
|Allen W. Sherzer |   DETROIT: Where the weak are killed and eaten.         |
|   [e-mail]   |                                                         |
+---------------------------------------------------------------------------+

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

Date: 5 Jun 91 18:58:24 GMT
From: pmafire!uudell!sequoia![e-mail]  (John K. Gibbons)
Subject: Lunar gravity in movies, was Re: Moonbase movie *Plymouth*

In article <[e-mail]> [e-mail] (Frank Crary) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>>  [... difficulty and desirabilty of portraying movement under 1/6 G ...]
>
>I would think it would be almost impossible. There is no actual data
>on how people would walk under these conditions. The Apollo LM was too
>small to do any real walking in. The problem you refer to might not ever
>exist for slower motions (e.g. a reasonably slow pace.) ...
>
>                       Frank Crary

A combination of attention to walking style, occasional use of slow-motion,
and just ignoring the issue for more static shots might succeed.  As Frank
Carey says, we don't really know what normal gait in a shirt-sleve Lunar
habitat would be like.  However, slow motion (_not_ necessarily at 1:6,
just enough to convey that steps can be longer, falling slower, stopping
more difficult, etc.) would enhance verisimilitude -- which is after all
not quite the same as accuracy or truthfullness.

--

----------------------------------------------------------------------------
John K. Gibbons                   |   UUCP:  ...!cs.utexas.edu!execu!jkg
Comshare, Inc.   Austin, Tx.      |   Internet:  execu![e-mail]
#include "std.disclaimer"         |              [e-mail]
----------------------------------------------------------------------------

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

Date: 5 Jun 91 23:29:08 GMT
From: udecc.engr.udayton.edu!blackbird.afit.af.mil![e-mail]  (TS Kelso)
Subject: NASA Prediction Bulletins:  Space Shuttle


The most current orbital elements from the NASA Prediction Bulletins are
carried on the Celestial BBS, [phone], and are updated several times
weekly.  Documentation and tracking software are also available on this
system.  As a service to the satellite user community, the most current
elements for the current shuttle mission are provided below.  The Celestial
BBS may be accessed 24 hours/day at 300, 1200, or 2400 baud using 8 data
bits, 1 stop bit, no parity.

STS 40
1 21399U 91 40  A 91156.61632683  .00103988  00000-0  25599-3 0    22
2 21399  39.0093 332.9214 0014542 346.9167  13.1696 15.94684099    07
--
Dr TS Kelso                           Assistant Professor of Space Operations
[e-mail]          Air Force Institute of Technology

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

Date: 5 Jun 91 07:33:40 GMT
From: agate!spool.mu.edu!rex!wuarchive!emory!wa4mei!ke4zv![e-mail]  (Gary Coffman)
Subject: Re: Microgravity?

In article <[e-mail]> [e-mail] (Herman Rubin) writes:
>In article <[e-mail]>, [e-mail] (Bev Freed) writes:
>
>            .....................
>
>> A 710-meter shaft set deep into the Earth forms the centerpiece of a
>> new microgravity experimentation facility which will open in July.
>> The center is expected to make a significant contribution to
>> biotechnology, metallurgy, ceramics, and other space related
>> research.
>
>            ..................
>
>I must be missing something.  How do we get microgravity at this depth?
>The formula I recall would have the gravitational force there approximately
>.9999 g.

Think free fall drop shaft. You get about 117 seconds of free fall in a
710 meter shaft. Lots of Gs at the bottom though. :-)  Assuming that they
intend to slow and capture the samples more gently than splat, the amount
of free fall time will be reduced. I'm guessing that they plan to evacuate
the shaft to avoid turbulence during the drops, otherwise the elevator
shaft of a tall building would suffice.

Gary

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

Date: 6 Jun 91 01:08:23 GMT
From: agate!spool.mu.edu!rex!wuarchive!zaphod.mps.ohio-state.edu!usc!isi.edu![e-mail]  (Craig E. Ward)
Subject: Re: RFD:  talk.politics.space

In article <[e-mail]> [e-mail] writes:
>...
>    As easily as creating a political subgroup, we might of created a more
>technical subgroup (as has been suggested).

A technical mailing list already exists, (No, I don't have the info on it
handy.) just as a commercial, investors, list also exists.  Each mailing list
might be large enough to support subgroups.  Any conventional wisdom on how
big a list should be before moving to a newsgroup?  100? 500?
--
Craig E. Ward <[e-mail]>     Slogan:    "nemo me impune lacessit"
USPS:    USC/Information Sciences Institute
    4676 Admiralty Way, Suite 1200
    Marina del Rey, CA 90292

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

Date: 5 Jun 91 18:34:53 GMT
From: dimacs.rutgers.edu!morley.rutgers.edu![e-mail]  (Mark Purtill)
Subject: Re: More on Freedom Vote

[e-mail] (Matthew DeLuca) writes:
>In article <[e-mail]> [e-mail] writes:
>>In article <[e-mail]>, [e-mail] (Matthew DeLuca) writes...
>>>As for the production line bit, the production line was closed when
>>>Challenger blew up, and yet we have Endeavour.  I'll believe you when
>>>they destroy the tooling used in making shuttles.

>[I meant to say before Challenger blew up, not when.]

>>Yup.  Of course, now that they've assembled Endeavor, they no longer have the
>>stock of spare parts they did before Challenger blew up.

>Actually, I understand that the spare part situation is better now than it
>was before; they were cannibalizing parts from one shuttle (usually Columbia)
>to keep the others flying; this has been rectified.

    Different spare parts.  The spare parts used to make Endevour
are "structural spares", which I gather are things like spare wings
(well, maybe not wings, but big chunks) which are not swapped between
shuttles.  The parts that were being swapped were much smaller things,
maybe up to main engines.  They still are swapping things; for
instance, when the had the problem with the external fuel connection
thingee, either Atlantis or Discover flew with Endevour's.
    The structural spares are being replaced, I think; in the
budget comparison posted a while back as part of the Fred flamage,
there's a line under Space Transportation for them.  (The subcommittee
mark-up with Fred would have cut $75 million from it (out of how much,
I have no idea) over what they actually passed.)  There may be a
danager, however, of the shuttle production lines closing after
they're built -- I seem to remember the last set of structural spares
was funded partly to keep the production lines open, as otherwise
Rockwell was going to start building B-1's there.

^.-.^ Mark Purtill         [e-mail]         [phone] (O)
((")) DIMACS, P.O. Box 1179, Rutgers U., Piscataway, NJ 08855 [phone] (H)
****** I'm moving on or about August 24th; watch this space for details. ******

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

End of SPACE Digest V13 #697
*******************