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/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests)
ID </afs/andrew.cmu.edu/usr1/ota/Mailbox/ccLkiUO00WBwQ3Rk5l>;
Wed, 19 Jun 91 03:45:36 -0400 (EDT)
Message-ID: <ccLkiOW00WBwA3Q04=@andrew.cmu.edu>
Precedence: junk
Reply-To: space+@Andrew.CMU.EDU
From: space-request+@Andrew.CMU.EDU
To: space+@Andrew.CMU.EDU
Date: Wed, 19 Jun 91 03:45:31 -0400 (EDT)
Subject: SPACE Digest V13 #666
SPACE Digest Volume 13 : Issue 666
Today's Topics:
Re: Help for science writer
INFO: Clandestine Mars Observer Launch??
Re: Beanstalk analysis reprise
Re: Moonbase movie *Plymouth* to air Sunday?
Re: satellite refuelling
Re: The Reasons for a Station? Was Re: Rational next station design...
Re: Extra Terrestrial Intelligence
Administrivia:
Submissions to the SPACE Digest/sci.space should be mailed to
space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests,
should be sent to space-request+@andrew.cmu.edu, or, if urgent, to
UUCP: ..uunet!tarpit!bilver!vicstoy!dona 0110 0110 0110 Just say NO!
Illuminati < MJ-12|Grudge|TLC|CFR|FED|EEC|Bush > WAR = "New World Order"
------------------------------
Date: 31 May 91 06:18:04 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!rpi!news-server.csri.toronto.edu!torsqnt!geac!torag!w-dnes!waltdnes@ucbvax.Berkeley.EDU (Walter Dnes )
Subject: Re: Beanstalk analysis reprise
wreck@fmsrl7.UUCP (Ron Carter) writes:
> Note: This analysis is of the static case. It ignores
> tidal considerations which are important to objects in the
> Earth-Moon-Sun system. A working beanstalk will require
> damping mechanisms to compensate for tidal forces. Dynamic
> momentum-transfer devices such as vertical Lofstrom loops
> or space fountains could also transmit forces from far up
> the tether back to the earth, reducing the tether's taper
> and the amount of material required.
I get to play the devil's advocate again. I don't like to
destroy people's dreams, but a reality check is in order here.
Your calculations seem to be based on an airless earth, i.e a
good vacuum. Don't forget that we have an atmosphere. I briefly
considered cross-posting this followup to sci.geo.meteorology,
but decided not to since it's all in support of a theoretical
space discussion. Some questions to consider...
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 (150 mph)
jetstream somewhere in the stratosphere ? Can you supply some
typical "Asurf" values along with the taper as a function of
height. I work in the Atmospheric Environment Service, (Canada's
weather service) in a unit that calculates meteorological
parameters for construction. Just down the hall from me, our
industrial meteorologist does recommendations for CSA-S37, the
design standard for antenna towers in Canada. I'd like to ask
her to calculate the wind loading on the lowest (and thinnest)
portion of the beanstalk.
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.
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 ?
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.
5) What about charged particles in the van Allen belts
"doping" the crystalline structure of the beanstalk ?
Questions 4 an 5 are important because you need the great
strength of a pure "whisker". Chemical impurities and crystal
irregularities will decrease the strength to the breaking point.
I remain a skeptic re: tethers/beanstalks. I hope against
hope that I'm proven wrong, but I think that the real-world
problems are insurmountable.
Walter Dnes
-------------------------
waltdnes@w-dnes.guild.org
73710.3066@compuserve.com
------------------------------
Date: 1 Jun 91 08:51:52 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!think.com!mintaka!ogicse!plains!person@ucbvax.Berkeley.EDU (Brett G Person )
Subject: Re: Moonbase movie *Plymouth* to air Sunday?
Is this a pilot? Could be a neat series. Especially if the moonwere
to suddenly be ripped out of oorbit and....
H
ope they make it a series. We could use a good SF network show again.