Can we now build the space elevator?

===========================================================From: Robert Clark ( snipped-for-privacy@yahoo.com) Subject: Re: beanstalks (was Re: Metallic hydrogen ...)
Newsgroups: sci.physics, sci.astro, sci.space.policy, sci.materials, sci.energy Date: 2004-06-09 02:06:53 PST
snipped-for-privacy@spsystems.net (Henry Spencer) wrote in message

Tie? Hmmm. Do you think it might work to tie the ends together of the 20 centimeter long nanotubes already produced? Looking up some links on knots, the knotted ropes always have less strength than the single, unbroken ropes. I confirmed this by testing on sewing thread. Still it might be interesting to find out how strong they are compared to single nanotubes.
Bob Clark =========================================================== Testing with thread confirmed that a break always occurred where two strands were tied together. However, to estimate the strength of a single strand of thread, I wrapped two ends around my fingers and found that the break occurred in the middle of the thread, not where I was holding the thread. My guess was that the softness of my fingers prevented the thread from breaking at the attachment point (where I was holding it.) I confirmed this by holding one end by a pair of pliers and the other end with my fingers. The break occurred where the pliers held the thread. However, when I put a soft cloth between the thread and the pliers, the break occurred in the middle of the thread, as when I was holding both ends with my fingers. I imagine this must actually be a common way of testing tensile strength. That is, you don't want to attach the strand or rope to something that will make the rope break at the attachment point. This would give an invalid measure of the rope strength. You want it to break somewhere in the middle. I therefore suggest connecting together the already produced 20 centimeter long nanotubes with a soft material or by whatever means used to insure nanotubes don't break at the attachment point during tensile strength testing. This will allow the full strength of the nanotubes to be maintained even when they are connected together. What will need to be investigated is what soft material will also be light enough so as not to cancel out the weight savings of using the nanotubes. Note that this soft material might be heavier than the nanotube material but because it only has to be used at the connections it can be quite small so quite conceivable may only add minimally to total weight. It still needs to be confirmed that the macroscopic sized nanotubes really are as strong as the nanotubes tested on the microscale. This report showed that 20 centimeter interwoven strands were significantly weaker than the tested individual microscale nanotubes:
Direct Synthesis of Long Single-Walled Carbon Nanotube Strands. Science, Vol 296, Issue 5569, 884-886 , 3 May 2002 http://www.sciencemag.org/cgi/content/full/296/5569/884
However, the theory is that this is because there were many single nanotubes connected together by weaker van der Waals forces rather than the stronger carbon-carbon molecular bonds that prevail in individual nanotubes. This is explained here:
Pulling nanotubes makes thread http://www.trnmag.com/Stories/2002/103002/Pulling_nanotubes_makes_thread_103002.html
What still needs to be tested is the strength of the *individual* nanotubes that make up these 20 centimeter long strands.
This article describes a group that proposes that competively offered prizes could make possible the technologies required for the space elevator by 2010:
Space elevator contest proposed. ‘Elevator:2010' aimed at encouraging technology development. http://www.msnbc.msn.com/id/5792719 /
Bob Clark
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snipped-for-privacy@yahoo.com (Robert Clark) wrote in message

http://www.trnmag.com/Stories/2002/103002/Pulling_nanotubes_makes_thread_103002.html
The vibration resonance, must, be damped somehow. And to use lines like guywires from the earth is required.
So in effect a flexible tower must be built.
And then the tower must be supported from above, because the light weight material would collapse otherwise.
And to get the power from above means the earths weight and the satilites weight must be considered.
Meaning the maximum power from the orbit causes the light weight wires.
And the limit of power is a fractional percentage of the satilite mass.
So a very heavy satilite like the moon is needed.
So given the true artifical satilite what is the mass of the material necessary to dampen the resonances.
And here the meaning of absolute damping indicates that even 1 Hz will break the tower.
Think of the skyscrapers wind problem.
It will only get worse.
So in between the solid tower and the thin wire is the answer.
How small a tower is required should be your question.
Certainly a pryramind could be built. Why not get started. A fifty mile high prymaind!!!!
Maybe fitey centurues of 1 million dozers!!!
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In sci.physics snipped-for-privacy@yahoo.com wrote: <snip>

You can damp the resonances, at least some of them, by moving the anchor point a bit, winching in and out the tether at both the bottom and the counterweight.

Why would there be power from above?
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wrote:

The satillite is revolving and the difference of one place to another is the time difference.
And to go from one time to another allows the force of Einstein to cause the power of lifting.
A delta-vee of the satillite is available to lift the threads.
Douglas Eagleson Gaithersburg, MD uSa
note: another way to cause the power is to allow the revolving satillite a drag that will not decay the orbit. And it is a fact that some orbits do not decay.
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I hate to rain on everyone's space elevator dream..
Until a fiber with the required tensile strength can be produced in the required lenghts it will never happen. When this amazing new material becomes a proven technology then things like space elevators might someday work.
The hype I hear about space elevators being around the corner (so to say) is really optimistic. Its not easy to make a perfect fiber tens of thosuands of miles long, let alone a nanotube. Bulk produced 70 Gpa TS fibers would enable more than just space elevators. But I'd rather not count chicks before they hatch.
Its not as bad as planning to build a NRE with 20,000 kelvin exhast temperature using nothing more exotic than regenerative cooling to keep it from blowing up. Gee.. all we need is a ceramic that melts 25,000 Kelvin! Why that kind of discovery is just 30 years away. Buahahahaa!
Seriously though, whoever finds a way of making nanotube fibers in bulk for cheap will be a gahgillionare.
good luck all
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aSkeptic wrote:

I like the term "beanstalk" better.. surprised nobody has mentioned that word since that is basically what it is, and has been in and out of sci-fi lo these many years.
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The term "beanstalk" is a specific kind of fantasy. It's the straight-up, does not move much, counter-weighted past 24 hour orbit type of space elevator. Also called a "sky hook." There are other designs of space elevator, with various levels of requirement for stupendous new types of cable. Near as I can tell, all of them require huge increases in the strength of cable over any material presently manufactured. Like three or four orders of magnitude at least.
When somebody has manufactured a kilometer long cable strong enough to do the job, call me. So far, these nano-tube things have only been a few cm long at most. Also, I'd like to see a few failure mode analysis calculations before I get invested in any such project. Socks
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puppet snipped-for-privacy@hotmail.com wrote:

No, more like 2..3 X Average breaking strain of current nanotubes is ~30-50 GPa. The highest recorded breaking strain was 63 GPa.
Steve
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Strength of nanotube is *not* strength of cable, nor more so than, for example, the strength of single crystal aluminum whisker is the strength of manufactured aluminum. Attempts to represent breaking strength of current nanotubes as indicative of the strength of a bulk cable is downright misleading.
Mati Meron | "When you argue with a fool, snipped-for-privacy@cars.uchicago.edu | chances are he is doing just the same"
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Beanstalk seems to have not caught on in the space elevator community. Space Elevator sounds clunky and giggle-inducing but the consensus (or lack therof) seems to be that a stationary ground-to-orbit tether shall be called 'space elevator'.
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economic snipped-for-privacy@yahoo.com (E.R.) wrote:

`------------------------------------------------------------------'
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That would certainly help to meet payroll.
~er
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I have invent another type of space elevator, which avoids ALL the previous problems. It uses Helium filled balloons connected to a Chair, with a panel. The person sits in the chair and presses the button on the panel, which cuts the cord that has been holding him to the ground. The panel also provides a wrap around effect that the person sees as the interior of an elevator. He rises up, and up and up, till he gets to his floor and gets off. No structure needed, no vibration dampening No power needed at all!
I haven't figured out how to go down yet. that is next.

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On Sun, 29 Aug 2004 23:36:10 -0500, "Ted John Kerry Kennedy"
[snip]
TOP POSTING SUCKS.

A handgun. It worked for the guy who floated over LAX.
or...
A bowie knife and a parachute.
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[snip]
You might want to check what is the altitude record for balloons.

Actually, that part is easy. You just step out the door. Socks
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BB gun should work. LOL
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snipped-for-privacy@yannitell.com (aSkeptic) wrote in message

Dort! NRE should be NTR or nuclear thermal rocket
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snipped-for-privacy@yannitell.com (aSkeptic) wrote in message

Of course a 70 Gpa fiber is required before a space elevator can be done. It could well turn out to be, like AI, one of those things that's just around the corner for a very long time.
But it can't hurt to think about, plan for it and so forth. Think what a position you would have been in if you could have anticipated in the mid-70s what micro-computers would do and how much of an industry they would be.
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economic snipped-for-privacy@yahoo.com (E.R.) wrote in message

Well it might hurt to plan for someday that never comes. However, it is a lot of fun to dream (and I do so as much as I can afford to). Space elevators, if in the end profitable, is only the tip of the iceburg for super fibers. The feller who makes this possible would be as important as Bessemer (and hopefully as rich or richer).
If you ever want to say, can you give me change for this million dollar bill, I suggest figuring out how to make cheap ultra strong fibers.
-scott
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Dear aSkeptic:
...

Another hundred years or so, and that'll get you a tank of gas...
David A. Smith
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