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 news:...

... > Given that the nanotubes themselves are far thinner than even a one-micron > ribbon, any material technology that ties them together into bulky > materials should work just as well for such ribbons, with some adjustment > in the details of manufacturing. Even such a ribbon *is* a bulky > material, when the fibers involved are nanotubes. > ...

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

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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

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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.

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Bob Clark

Reply to
Robert Clark
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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!!!

Reply to
eagleson2004123

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?

Reply to
Ian Stirling

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.

Reply to
eagleson2004123

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

Reply to
aSkeptic

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.

Reply to
Morituri-Max

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.

Reply to
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.

Reply to
Eric Gisse

You might want to check what is the altitude record for balloons.

Actually, that part is easy. You just step out the door. Socks

Reply to
puppet_sock

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

Reply to
puppet_sock

BB gun should work. LOL

Reply to
aSkeptic

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'.

Reply to
E.R.

Dort! NRE should be NTR or nuclear thermal rocket

Reply to
aSkeptic

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.

Reply to
E.R.

That's because it sounds ridiculous. One half-expects a proposal for a beanstalk to come with a side plan involving golden-egg-laying geese.

It sounds neither clunky nor giggle-inducing (*) to me.

- Joe

(*) Or at least, not nearly as giggle-inducing as something from a fairy tale.

,------------------------------------------------------------------. | Joseph J. Strout Check out the Mac Web Directory: | | snipped-for-privacy@strout.net

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Reply to
Joe Strout

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

Reply to
Steve Taylor

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"

Reply to
mmeron

Err, you don't need a fiber that long.

You need a fiber long enough that the matrix the fiber is in can load the fiber to failure if you pull on the ends of the rope, and also adhered well enough that the ends of each fiber don't pull loose.

Wool twine has a tensile strength of nearly the same as wool fiber, but the individual fibers are only a couple of inches long.

Reply to
Ian Stirling

Perhaps you are old enough to remember the earlier "carbon fiber Beanstalk" hype.

If you allow yourself to fantasize that you will be able to get 60% of the theoretical strangth of the graphite crystal..... then you can believe that the "carbon fiber Beanstalk" is feasible.

IT is this belief that one can get these amazing high fractions of the theoretical strength that is the insanity of self delusion.

LOOOONG time to wait for the realization.

HYPE.

JIm

Reply to
jbuch

I don't recall the initial hype over bean stalks or teathers, I think this is before my interest in materials science.

Imagine what would happen if PAN carbon fiber products came down to

1/100th their current (already inflated) cost. PAN fiber is outrageously expensive, last I checked it was about $40 per pound. Weave it in 3 dimentions, pressure infiltrate it with phenolic resin (pitch) and pyrolize it and now you are talking and even more disgustingly expensive material. Lightweight, strong, and solid at high temperatures, C-C composites can be a great material if you can keep oxygen and nitrogen away from it. Last time I looked at carbon fiber it was $40 per pound bulk.

Heck.. If PAN fibers could be made for less than a dollar per pound we might see a revolution in manufacturing. It might not be like the invention of steel, but certainly as important as the invention of aluminum.

And Nanotubes would be even more impressive. I'd prefer boron nitride fibers but I'm not picky. How about a super fiber for less than $1 a pound!

Imagine a twin engine electric powered 4 seat cesna with a pressurized cockpit with less mass than an ultralite. Or Briges spanning nearly a half a mile without any ground supports! You could place a brige anywhere you pleased! Think of what this could do for transportation in big citys. Traffic clogged? Just add a couple more elevated roads. Wouldn't be too great for cars, gotta have some mass to keep it from being blown off the road from a light breaze :)

cheers,

Scott

Reply to
aSkeptic

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