Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_6/V13_667.TXT

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Subject: SPACE Digest V13 #667

SPACE Digest                                     Volume 13 : Issue 667

Today's Topics:
        Re: Tethers (was Re: Laser launchers)
  Pregnancy in space (was Re: Rational next station design process)
                Re: lifeboats
                Re: lifeboats
            Re: Alien Astrophysics
              Re: SPACE Digest V13 #577
              Re: SPACE Digest V13 #580
             Re: Antenna testing
             Re: Antenna testing
               How was San Antonio SDC?
         Re: Moonbase movie *Plymouth* to air Sunday?

Administrivia:

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  [e-mail].  Other mail, esp. [un]subscription requests,
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----------------------------------------------------------------------

Date: 27 May 91 20:14:03 GMT
From: usc!elroy.jpl.nasa.gov!jarthur!nntp-server.caltech.edu![e-mail]  (Earl A. Hubbell)
Subject: Re: Tethers (was Re: Laser launchers)

[e-mail] (Lydick, Carl) writes:

>In article <[e-mail]>, [e-mail] (Walter Dnes    ) writes...
>>
>>[e-mail] (Christopher Neufeld) and
>>[e-mail] (Earl A. Hubbell)
>>
>>     have both responded to a previous posting of mine. They point
>>out that tethers work better if tapered, rather than a uniform
>>thickness (my example assumed a uniform thickness). However, as
>>Earl Hubbell has pointed out...
>>
>>> Note that you
>>> do pay a price for exponential taper - the total mass of your
>>> cable system goes up >very< fast - a severe consideration for space work.

>Afraid not.  You GAIN by using the exponential taper.  The proper exponential
>taper is on that has constant tension per unit cross-sectional area for the
>entire length of the tether, and you pick that value to be close to the
>breaking strain for the material.  Any other geometry is going to require more
>material than an exponential taper, for a given strength/weight ratio for your
>material.

    Um...after having been semi-quoted - the point I was trying to
make with that statement was that while you can build tethers of any
length with just about any material by choosing a proper geometry, the
mass increases very quickly as your strength to weight ratio drops. I.e.
steel gives ridiculous masses, while (pick strong, light material of
choice) gives a much more reasonable mass for cables of lengths one is
likely to see, but in all cases the mass of the cable grows as an
exponential function of the length.
    I was comparing it to the 'straw man' of a simple linear cable -
which simply >breaks< in the example given.
    Perhaps it was a poorly chosen statement :-). My apologies.

>Carl J Lydick    HEPnet/NSI: SOL1::CARL    Internet: [e-mail]
--
Earl Hubbell -- [e-mail] -- Opinions expressed: mine
"There's a whole new breed of scientist out there today:  They drink,
smoke, fool around with women, but they won't answer one simple
question:  How do you destroy Washington, D.C.?" -villian, Matt Helm flick

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

Date: 28 May 91 16:32:05 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!think.com!linus!linus!cyclone![e-mail]  (S. J. Okay)
Subject: Pregnancy in space (was Re: Rational next station design process)

In article <[e-mail]> [e-mail] (Frank Crary) writes:
>In article <[e-mail]> [e-mail] (George William Herbert) writes:
>I think a "LabRatSat" would be limited by the lifetime of a rat. (Anyone
>know how long that is, I think less than 2 years...) Since there might
>well not be a next greneration of rats. (e.g. if they all were in individual
>cages, or due to zero-gravity pregnency problems...)

Just how much of a problem is this? I would think that given the the fetus is already
floating weightless inthe amniotic sac during its development, the absence of
gravity wouldn't be that much of a problem (but then, I'm no MD either).
Just curious, as I've seen this brought up here enough time to fire
my curiosity.

Thanks,
---Steve

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

Date: 29 May 91 04:51:22 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!rpi!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: lifeboats

In article <[e-mail]> [e-mail] (Fraering Philip) writes:
>I think I have seen ref. to the CM having translation
>capabilities. When the thrusters around the top side of
>the base and the bottom side are taken into account,
>it should have translation...

Not really.  I checked the CSM news reference, and confirmed my recollection:
by design, the CM system was purely attitude control.  There were only 12
thrusters, and no attempt was made to locate them symmetrically.  It might
have been possible to do translation in one or two directions, by firing
unusual combinations, but there simply weren't any thrusters pointing in
some directions, and in most of the others the thrust was far off center.
--
"We're thinking about upgrading from    | Henry Spencer @ U of Toronto Zoology
SunOS 4.1.1 to SunOS 3.5."              |  [e-mail]  utzoo!henry

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

Date: 29 May 91 15:07:36 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!caen!ox.com!fmsrl7![e-mail]  (Ron Carter)
Subject: Re: lifeboats

In article <[e-mail]> [e-mail] (S. J. Okay) writes:
>A small kick-thruster package to
>get you pointed in the right attitude for re-entry is about all you
>need for a lifeboat.

Only for a ballistic capsule a la Soyuz, which gives a rather
rough ride on the way down; peak G's are very high.

Apollo was a lifting capsule design (had to be in order to hold
itself in the atmosphere while moving > 18000 MPH).  In order
to direct the lift in the proper direction, it is necessary to
have active attitude control.  A lifting capsule can hold itself
high in the atmosphere and brake more slowly, giving a much
nicer ride down.

I very much doubt that making a thruster system which can be
stored reliably for > 1 yr before use is a problem for US
space technology.  We have proven systems on the Pioneers
and Voyagers which have been running for over a decade.

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

Date: 29 May 91 17:29:09 GMT
From: convex![e-mail]  (Richard A. Schumacher)
Subject: Re: Alien Astrophysics

I just sent mail to Mr. Fraering saying that the whole range
of fusion reactions would still be taking place in concentric
shells of a core, even if it had already detonated at the
center, but now I wonder: how would the huge neutino flux
influence the various fusion reactions?

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

Date: Wed, 29 May 91 18:47:34 EDT
From: [e-mail]
Subject: Re: SPACE Digest V13 #577
Newsgroups: sci.space
Cc:

In article <[e-mail]> you write:
>
>Paleolithic to Neolithic    Wood (Probably)
>Agricultural to Industrial  Coal
>Industrial to 'Post modern' Oil, Nuclear
>
>These sources all appeared unlimited to the ones who started using them, but
>we now know they are all limited.

Nuclear's limits are very far away.  Uranium in breeders will last
for thousands of years, even at many times the current world energy
use.

> Look around the major cities (even minor ones nowdays).  They are lit by
> oil.  They are full of devices that use oil.  The materials were mined
> and refined (glass, steel, etc) with oil-based energy.  The food eaten
> by the inhabitants was fertilized by oil-produced compounds.  Etc, etc.

Cities in the US are lit by electricity, of which only a very small
fraction (about 5%) is generated by burning oil.  Most comes from
coal, nuclear, hydro and natural gas.

Petroleum enters into the manufacture and transport of glass and steel,
but the primary energy input in their manufacture is coal (for steel)
and (I believe) natural gas (for glass).  Oil is certainly not
absolutely necessary.

The primary energy input in fertilizer manufacture is natural gas.
It is used to make hydrogen for synthesis of ammonia.  Any souce of
hydrogen would do, however.

Powersats may, someday, produce electricity, but by that time
competing technologies, including fast breeders, will be well
advanced.  Nuclear reactors can also produce process heat at the
Earth's surface without conversion to electricity, which is not
possible with powersats.

Powersats and space industrialization are not necessary to save
civilization from collapse anytime soon (read: for many centuries,
if then).  The beginning of "The High Frontier" screwed this up
badly.

    Paul F. Dietz
    [e-mail]

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

Date: 30 May 91 14:51:37 GMT
From: mentor.cc.purdue.edu!pop.stat.purdue.edu![e-mail]  (Herman Rubin)
Subject: Re: SPACE Digest V13 #580

In article <[e-mail]>, [e-mail] writes:
> Re: Unrestricted Launches;
>
> >>>What we need is for the government to allow those who want to do it to
> >>>do so without restriction from government restrictions.
>
> >>Sounds good to me -- what *specific* restrictions are currently
> >>preventing private and non-profit organizations from pursuing space
> >>exploration and development?
>
> >Essentially any launch must be approved, no matter where it occurs.

> Speaking of getting beyond this type of restriction, I learned a while back
> that there were a few proposals that involved creating a space-port somewhere
> on/near the equator.  Not only for the orbital energy advantage, but also as
> a base to improve international space relations, or even a home for an inter-
> national space admin.

This does not even address the problem.  The present law prohibits individuals
who are American citizens (I do not know the precise limitations) from launching
anywhere without permission.  I understand that the ARRL had to get permission
to launch an amateur radio satellite on Ariane.

Secondly, having an international space administration instead of the US
government would make things even worse.  I cannot imagine any earth
government being desirous of having a significant human presence in space
not firmly under the thumb of earth.  There are a few countries now in which
there is still enough freedom to hopefully get them to allow significant
free human activity in space, and a few small countries which recognize
that they are not in a position to block space activity might cooperate.

But will the US, USSR, China, India, etc., let them get away with it?

> I guess India was quite vocal about their wish to be the place for such a
> facility (though most equatorial nations recognized the benefit of a space-
> port for their economies and expressed interest)
--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: [phone]
[e-mail] (Internet, bitnet)   {purdue,pur-ee}!l.cc!hrubin(UUCP)

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

Date: 30 May 91 15:14:55 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!rpi!news-server.csri.toronto.edu!utgpu!cunews!mitel!testeng1![e-mail]  (Chris Stanfield)
Subject: Re: Antenna testing

In article <[e-mail]> [e-mail] (Bruce Dunn) writes:
>
>     Difficulty in unfurling antennas (and solar panels) seems to be one of the
>major causes of satellite and spacecraft failures (Galileo, newly launched
>Anik, nearly Gamma Ray Observatory).

Would it be feasible, with shuttle launched payloads, to deploy the
antennas before the IUS is fired? This would mean that the satellite
would be more easily recovered, or just repaired then and there, if
there were some kind of deployment problem. Maybe, with all the
antennaes, etc. deployed, the ground-based people could do a more
thorough system test before the satellite was boosted in higher orbit.
One of the problems with Anik is that it doesn't, apparently, have
enough fuel to get it down an orbit where the shuttle could pick it
up, assuming that to be a cost-effective and readily available
solution :-). There is obviously no problem with aerodynamic stresses
and satellites certainly have at least some maneouvering capability
with everything deployed. Am I out to lunch or is this feasible? Would
increased engineering costs make it not worth while? Not to mention
lack of shuttle launch spaces!

Chris Stanfield, Mitel Corporation: E-mail to:- uunet!mitel!testeng1!stanfiel
[phone] Ext.4960
We do not inherit the world from our parents - we borrow it from our children.

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

Date: 30 May 91 16:37:41 GMT
From: bonnie.concordia.ca!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Antenna testing

In article <[e-mail]> [e-mail] (Chris Stanfield) writes:
>Would it be feasible, with shuttle launched payloads, to deploy the
>antennas before the IUS is fired?

Only if the antennas (a) can take the acceleration loads, and (b) won't
upset the center of gravity.  Unfortunately, acceleration loads are often
an issue.  The hardware is typically lighter if it doesn't have to take
upper-stage accelerations after deployment.  On-board thrusters typically
are small and induce only quite low accelerations.

There are also sometimes other constraints.  Galileo, in particular, had
no choice because its antenna had to stay hidden behind the sunshade until
after the first Earth encounter; it wasn't designed to operate inside of
Earth's orbit.
--
"We're thinking about upgrading from    | Henry Spencer @ U of Toronto Zoology
SunOS 4.1.1 to SunOS 3.5."              |  [e-mail]  utzoo!henry

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

Date:     Thu, 30 May 1991 12:41 CDT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject:  How was San Antonio SDC?
Original_To:  SPACE

I had to miss attending the National Space Society's Space Development
Conference in San Antonio last week.

So how did it go?  Can anybody give us a report?

     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |     Bill Higgins   Fermi National Accelerator Laboratory
 \       /     Bitnet:     [e-mail]
   -   -       Internet:  [e-mail]
     ~         SPAN/Hepnet:      43011::HIGGINS

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

Date: 31 May 91 03:54:07 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!rpi!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Moonbase movie *Plymouth* to air Sunday?

In article <[e-mail]> [e-mail] (Lance Franklin) writes:
>I also noted that they seemed to have an explosive device that blew a plug
>to open a passage for air to compress the airlock in an emergency.  Perhaps
>I'm a bit conservative, but I don't think I would particularly like to
>have an electrically-operated explosive device in a position where it can,
>if it blows accidentally, reduce the room to a vacuum in a few seconds.

In fact, they almost certainly would not have an electrically-operated
explosive device to do that, period.  The traditional space-hardware
preference for doing lots of things with pyrotechnics would have to be
severely modified or abandoned for a long-term colony with many relatively
unsophisticated people around.  Those things are dangerous even if they
*don't* reduce rooms to vacuum when fired.  Pyrotechnic hardware kills
people regularly.  They are accepted in current use because they can do
many jobs with very lightweight hardware.  For a lunar base, safety issues
would almost certainly take priority.
--
"We're thinking about upgrading from    | Henry Spencer @ U of Toronto Zoology
SunOS 4.1.1 to SunOS 3.5."              |  [e-mail]  utzoo!henry

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

End of SPACE Digest V13 #667
*******************