Uses of Bulk Nano Materials (was beanstalks)

Andrew Nowicki wrote: AN> The entire thread is ridiculous. AN> Armchair buckytubes conduct electric AN> current better than copper.
Henry Spencer wrote: HS> Which still isn't anywhere near good enough to HS> power a climber, not when the power has to be HS> transmitted tens of thousands of kilometers through
Buckytubes (also known as single wall carbon nanotubes.) have three kinds of crystallographic lattice: armchair, zigzag, and chiral. Drawing:
http://www.islandone.org/LEOBiblio/buckytubes.jpg
Armchair buckytubes are ballistic conductors, which means that their electric resistance is relatively small (6500 Ohms) and independent of length. If the armchair buckytubes are free of defects, one millimeter long buckytube has the same electric resistance as a buckytube that is one thousand kilometers long. Toroidal (or closed loop) buckytube would have no contacts, so its resistance would be extremely small. (Nobody knows how small.) The maximum current density of the armchair buckytubes is about one billion amperes per square centimeter -- 3 orders of magnitude more than the maximum current density of copper! Zigzag and chiral buckytubes behave like semiconductors.
I believe that armchair buckytubes could be used above the ionosphere and power the climbers -- high tension wires in North America transport electricity over hundreds of kilometers. Solar flares are a nuisance because they generate strong voltages in the conductive skyhook. I believe that dividing the skyhook into segments interspersed with line choke coils would solve this problem. Note that the armchair buckytubes are perfect wires for the coils.
If the skyhook is laid on the ground on the magnetic equator and strong electric current flows through it, the Earth magnetic field generates Lorentz force which levitates the cable. This is easier way to lift it into orbit than using the rocket launchers.
Although skyhook is theoretically possible, it makes no economic sense because it is vulnerable to terrorists and more expensive than related technologies: orbital slings and geomagnetic levitation. Orbital slings can be made now from relatively cheap, commercially available fibers. (By the way, I made a new thread in sci.space.tech named 'Levitating geomagnetic buckytubes.')
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I don't see why this has to be the case for a "beanstalk" if located in a isolated equatorial island. Any plane or boat coming anywhere near it could be detected and intercepted from hundreds of miles away.
Bob Clark
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Beanstalk was not mentioned in the holy Quran, so it is a kafir idea and it must be destroyed to save the world. We are going to mail our time bomb up the beanstalk so that it breaks it into two parts: the bottom part will plunge into the atmosphere, while the upper part will be hurled beyond the gravity of the earth.
Islamic Beanstalk Busters
La illaha illallah Muhammadum rasullullah!
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towelhead wrote:

Granted, you technically can say what you will (related to Mat. Sci.) on this news group. However, can you please try to respond to discussions with some small bit of respect/inteligence?
Seth
p.s. If you do as recommended by me, I'm sure that some lengthy, scientific and productive discussion (right or wrong on anyone's part) will ensue.
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Have you considered appling this idea to a non-tapered Rotator? It should help in using Rotators to move cargo to low orbits.
Earl Colby Pottinger
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Rotators strike me as a better idea than beanstalks. However, they may not be the best case for my pulley idea. Unlike a beanstalk which is lifting small masses up and down in the fashion of a continuous pipeline, rotators need to catch and throw fairly large masses at a time, with consequent big changes in tether tension. I'm not sure that pulleys are right for this regime. Furthermore, rotators can be used without much "elevating" at all. Catch at one angular position, release at another. Fine tune by shifting mass near the "hub". No need to shift mass near the tips.
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Earl Colby Pottinger wrote:

One of the great stupid things to do that I have seen recently is to talk about nanotubes with cross posting to a lot of different newsgroups.
The real smarts and the pseudo-smarts get into wars with each other.
To a large extent, the information content of the messages is dwarfed by the emotional content.
Really dumb thing to do, but then there are people who enjoy the flurry of semi-intellectual activity.
I will read about a dozen more elements of this thread and evaluate the usefulness of the time consumed in reading it.
Enjoy yourselves, as evidently does seem to happen.
sci.space.policy ...... ?????
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Welcome to the real world where a single invention/product can affect a number of people doing totally diffirent things. As it was I had trimmed out a number of newsgroups before I posted. It is my understanding that posting to more than three groups at a time is getting carried away.
Sci.Astro - Where the discussion started as far as I can tell.
Sci.Space.Policy - Where the discussion is make better rockets or can they be replaced with a beanstalk.
Sci.materials - What is the real state of the art in Nanotubes.
Earl Colby Pottinger
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Earl Colby Pottinger wrote:

I think you show bad taste, nevertheless.
However, at least people who want to endlessly discuss this subject in the sense of a disconnected semi-shouting match have kindly been provided this opportunity for endless discussion over a whole bunch of newsgroups.
This may be the real world, to use your phrase, but this "discussion" actually will have almost no significance to any of the participants.
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Earl Colby Pottinger wrote:

Sci.nanotech is more apppropriate, but the moderator would likely reject crossposting.
And there's the unmoderated alt.sci.nanotech.
--

You know what to remove, to reply....



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Dear Earl Colby Pottinger:
...

bulk
will
And yet the ignition of single flash bulb could ignite an entire structure? I think you are putting too much faith in a single technology. We need the stars, but in our eyes is the wrong place for achieving them.
David A. Smith
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No, it will not. That bright flash needs oxygen to get the burning going. You will not find oxygen available in either space or inside the resin bond fibers together - no to mention the resin will act like a heat sink preventing the rise in the nanotubes temperture. Check again, you claim only applies to single uncoated tubes under a very bright light.
Earl Colby Pottinger
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Dear Earl Colby Pottinger:

of
needed
structure?
the
going.
bond
only
This is what is documented, yes. And was totally unexpected.
Lightning strikes near the "cable", will induce sympathetic current in the cable. The heating can delaminate your cable, delamination in an area that is in full atmosphere.
Note that the coating you mention will act as an insulator, retaining the heat, so that a second "event", soon enough, will get it even hotter.
The highest loading should be outside the atmosphere, but it will be non-zero in the atmopshere. It wouldn't do to go drifting off... but then we are not talking about shadow square wire, are we?
David A. Smith
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The length of cable within the atmosphere -- especially within the region where lightning is an issue -- is such a small fraction of the total cable length that all kinds of special precautions can be taken there without increasing cable mass significantly.
--
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Dear Henry Spencer:
wrote:

the
that
cable
Sprites have been seen to 60 miles in altitude, and that is without a "lightning rod". Other than not having any one carbon fiber contacting any other, there isn't much you *can* do. Then there goes your strength.
David A. Smith
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There's lots you can do. Failing all else, you can probably just switch to Kevlar for the bottom 100km. It's only carrying its own weight, plus dynamic loads and cable tension -- it doesn't *need* that much strength.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
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Wouldn't magnetic storms induce strong currents along the whole length of the cable? You may need a few meters of kevlar every kilometer, all the way up.
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They might. I don't think this has been explored in detail.

Possibly, depending on how conductive our hypothetical nanotube-based material is. (It might not be very conductive; a good composite doesn't have the fibers themselves in contact with each other much.) I would hope it wouldn't have to be several meters every kilometer, because that might add quite noticeably to the cable mass. In general, doing *something* to the cable at intervals isn't a problem, provided the intervals are wide and the something isn't too massive.
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For what? Assuming a conducting cable, what circuit will the current take? And remember that although individual carbon nanotubes of some types are good conductors, they are not necessarily in good electrical contact. The elevator will not be a very good conductor, it's resistance over significant distances will be quite high.
--
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In sci.space.policy "N:dlzc D:aol T:com \(dlzc\)" <N: dlzc1 D:cox T: snipped-for-privacy@nospam.com> wrote:

Making the bottom 100 miles out of kevlar, or whatever is not a big problem. The only reason that nanofiber materials are needed is the huge taper implied if you tried to use conventional ones. For example, making the bottom 100 miles out of kevlar would only (about) double the total mass. If you tried to do it along the whole length, you'r looking at billions of times.
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