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Texas Scientists Spin Carbon Nanotube Fiber
RedCard writes "According to this article at news24.com, University of Texas scientists have managed to spin a fiber made of 60% carbon nanotubes that is five times stronger than steel and is "tougher than any natural or synthetic fibre described so far" - including spider silk! Previous attempts at making fibers like this have only produced relatively short lengths, but these guys have produced lengths of 100 metres at the rate of 70cm per minute!"
Not sure if that particular figure is accurate, but it sounds ballparkish. The reason the numbers don't seem to add up is that the gravitational pull will drop off with altitude. At the geosync point, where most of the mass is, the cable will be weightless (as it is in orbit). At the bottom, the cable will weigh the usual 9.8 N/kg (and will have to support its own weight, of course). In between, gravity drops off rapidly (1/r^2) as the cable ascends, putting less and less tension on the rest of the cable and making the achievable length of self-supporting cable much greater than it would be in a uniform 1g environment.
Range Voting: preference intensity matters
Yes, gravity drops off with 1/r^2 where r is the distance to the center of the earth. The first 300 km are not really significant compared to the radius of the earth which is 6400 km.
Anyhow, let's do it exactly. A segment of cable with length dr and a density (per length unit) rho has a mass dm=rho*dr. On this segment, two forces act:
1. Gravitional force (downwards) ,
d Fg = dm g0 (r0/r)^2
where g0 is the gravitation constant at sea level (9.8 N/kg), r0 is the radius of the earth (6400 km), and r is the distance to the center of the earth.
2. Centrifugal force (upwards)
dFc = dm w r,
where w is the angular velocity (2pi/24 hours = 7.3e-5 rad/s). We ignore the fact that g0 at sea level incorporates a neglegible centrifugal effect.
The total force F of this cable extending from sea level (r=r0) to some altitude R is
F = INTEGRAL(r0..R) (dFg - dFc) =
INTEGRAL(r0..R) rho dr (g0 r0^2 r^-2 - w^2 r), or
rho [g0 r0^2 (1/r0 - 1/R) + w(r0^2 - R^2)/2]. Assume that rho=1e-3 kg/m; R=3.5e7 m, r0=6.4e6 m. Then F = 4.8e4 N, the equivalent of 4810 kg of mass hanging at sea level, all to be supported by this 1-mm-thick supercable. If we would have assumed that the gravity didn't decrease with altitude and that the centrifugal effect didn't play a role, then 30,000 km cable would weigh 2.8e5 N, so it does help.
The tensile strength of steel is around 800 MPa, i.e. 1 sq. mm will break at 800 N (that corresponds to around 10 km hanging at sea level). If the hypothetical carboncable has a tensile strength that is 30x higher, then it would be able to support 800*30=2.4e4 N, which is at least in the same order of magnitude as what we need for the space cable.
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According to this page (which I'm not sure how much to trust due to bias, but has similar figures to what some Googling turns up), carbon nanotubes buildable in the forseeable future have a theoretical tensile strength of 130 GPa (versus current laboratory nanotubes having a measured tensile strength that varies in the range of about 10 GPa to 60 GPa, according to Google) and have a density of 1300 kg/m^3 = 1.3E-3 g/mm^3 (or 1.3E-3 kg/m for a 1 mm^2 bundled nanotube cable, which is pretty close to your plugged-in value). Assuming all your equations are correct (I'm a little too fuzzy-headed right now to check in close detail, but they look perfectly fine from here), then the top end of what single carbon nanotube can do today is already near-or-barely-past the minimum tensile strength (about 63 GPa, which is both the bandied figure and what your own equations indicate after plugging in the new density) required to build a self-supporting orbiting cable. Individual nanotubes are a far cry from actual cables, but it's something to work with. If the 130 GPa figure is attainable, then the elevator should have a very respectable margin for payloads.
Range Voting: preference intensity matters
I forgot to copy the square of omega (w^2) from my scratch paper to the comment. The correct equations:
dFc = dm w^2 r,
F = INTEGRAL(r0..R) (dFg - dFc)
= INTEGRAL(r0..R) rho dr (g0 r0^2 r^-2 - w^2 r)
= rho [g0 r0^2 (1/r0 - 1/R) + w^2(r0^2 - R^2)/2].
With rho=1.3e-3 kg/m (updated value); R=3.5e7 m, r0=6.4e6 m, g0=9.8 N/kg, w = 7.3e-5 rad/s, we get F = 6.3e4 N for the tension on the cable.
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One can estimate theoretically the ultimate strength of a nanotube be examining the microscopic failure modes, i.e. the ways in which atoms rearrange in response to an external stress (i.e. stretching). In the case of perfect, defect-free nanotubes, there are two modes that seem to be important. First, the rotation of a single carbon-carbon bond by 90 degrees, which converts a patch of 4 hexagons (remember that carbon atoms are arranged in a chicken-wire or honeycomb pattern on the tube wall) into two pentagons and two heptagons (relevant references are Zhang & Crespi from Penn State in Physical Review Letters and work by Bernholc at NC State and Yacobson at Rice I think, but the exact journal escapes me at the moment). This mode is a plastic distortion of the tube; the tube with the bonds rearranged is a bit longer than it was before. The second failure mode is for one of the hexagonal rings of carbon atoms to break open, i.e. for a carbon-carbon bond to break. This is a more catastrophic event, in that the tube then quickly breaks near the point of failure. Which way a tube fails may actually depend on how the honeycomb pattern is rolled into a tube shape. Now that's just the microscopic theory on the ideal, defect-free system. In a real tube, one expects there to be pre-existing defects in the structure. The failure under tension will then be at the defective points But, since nanotubes are so small, it's plausible that a single tube or bunch of tubes might grow entirely defect-free, in which case one can access the ultimate theoretical failure strength. Experiments on trying to stretch and break single bundles of nanotubes (Lieber's group at Harvard) show that one can extend a nanotube by about 6% of it's length before it breaks. This is in good agreement with the theoretical predictions mentioned above (and it's a legit prediction- the theory came first!). So it appears that in small enough systems, one can attain the theoretical mechanical strength.
Kudos to you, my good man.
Just imagine the uses for such a cloth made of this material... not to mention the obvious thing that comes to mind, "Hello Space Elevator!"
This could be the first truly fantastic scientific breakthrough of the 21st century. Now all we need is a room-temperature superconductor, and we're all set.
-- We live in a world where lemonade is artificial and soap has real lemon.
...but these guys have produced lengths of 100 metres at the rate of 70cm per minute!
:-)
Not bad.
At that rate we should have enough for a space-elevator in just a couple of years. (assuming they don't think of a more down-to-earth use for it in the meanwhile...)
(Spudley Strikes Again!)
Get me off this crazy planet!!!
Damnit, this all we need to build one of these. Someone get jumping on the design!!
All Troll + "offtopic" mods are meta moderated as "Unfair", because you abused the system.
Could this stuff, if produced cheaply enough in the next 20 years, be the end-all of condoms? It sounds like such a stupid thing to ask, but I've known more than one family that became one because latex just doesn't hold up sometimes.
Perhaps weird uses like this could really help out in the end?
Trolls make great pets. Adopt one today!
I seem to recall that a bright source of light can make carbon nanotubes burn up like ignited magnesium.
Yea, I'd be the first to wear or use this fabric.. "Smile for the camera!"
"No, wait!" *clic-FLASH* "AAAARGH THE HUMANITY!"
I'll bet this stuff would be bitchen for a fiberglass type substance. I had read somewhere that they have already tried it but ran into problems with "clumping" of the microscopic nanotubes. But now they are macroscopic, so problem solved. And at the rate they are creating the macroscopic fiber it would seem that they could quickly replace existing carbon/graphite composite materials.
Damn, this is going to really change the aircraft industry. Not to mention golf and tennis.
The effect only works with single walled carbon nanotubes, and even then only when in air. The effect actually happens because the tubes are very black and very porus, absorbing a large amount of light and rapidly converting it to a violent expansion of the surrounding Oxygen in the air igniting the nanotube. This will never occur if the tubes are incorporated into an epoxy string.
- "Hear that?! The percolations are imminent! Cease your ingress!"
It seems my chances of living to ride the space elevator have just increased.
:-)
AFAIK the space elevator requires a material roughly 30 times stronger than steel. True, these guys are "only" five times stronger, which leaves just another factor of five (ok, six) to reach the required strength. So in a way we are about half-way there
I'm not clear about the cost of their material, though. Anyone have an idea of how hard is it to create enough nano-tubes raw material to feed their process?
This is definately good news, but it is only about 1/6th the strength needed for the elevator. At 5 times the tensile strength of steel (4.2GPa) it matches the strength of graphite whiskers (21GPa).
The elevator becomes feasible at around 130GPa, so there is a little ways to go yet. It is only a matter of time now.
FWIW, the theoretical limit of CNTsis thought to be around 300GPa.
I wonder if this stuff could be use to make ultra-light bullet proof vests. Also, I'm sure exotic car manufactures such as Farrari would be interested in the stuff.
Life is not for the lazy.
Condoms have over 90% effectiveness when used correctly. If you want to know what will really keep population down...
People in first world countries use their free time to watch TV, and look at porn.
People in third-world countries use their free time to have sex and make babies, because they don't have TV's and computers.
I propose, that in order to prevent unsustainable overpopulation in third-world countries, we give them TV's!
Help people in third-world countries! Give them TV's!
Who cares about space elevator: But if it is *five times* stronger than steel, it must be also better than Immodium.
[Use with meal, do not exceed 120 meter recommended daily dose. Spiderman is a copyrighted work of art, ingesting Carbonfibre for this purpose without authorisation of Warner Bros is prohibited.]
I doubt that we will ever figure out - and I suspect that even if we did figure out we couldn't do much about it
Technology is there. When is someone both rich and smart going to fund it?
Too bad Highlift went down the toilet...
Tim
Omnia vestra castrorum habetur nobis.
Now if only we could use this theory to increase the proportion of intelligent babies by having only the stupid people watch TV. Well, I can't worry about that now, time to catch Friends, then a little Jerry Springer...
Sure I'm paranoid, but am I paranoid enough?
It may not be strong enough yet, but it won't be long. IT was only a few years ago that they made the first one at a rate of 0.4cm per minute. Give them 2-3 years and it will be all systems go for a space elevator. Then it will be all systems go for space. I volunteer to go to mars. Unless GWB makes it the space elevator illegal as it threatens US supremacy in space.
-- Karma Karma Karma Karma, Karma Chameleon - Boy George
whoa...
So much stronger than steel, I wonder if you could cut vegetables or cheeze with a taught piece. Or necks.....
Eat at Joe's.
"Baughman says his achievement is to improve on this method by using nanotubes made from carbon monoxide..."
So we just hook this thing up to the exhaust on my car, right?
Everyone concentrates on how strong these fibers are. I'm wondering just how thin they are -- there's an old SF idea of a "monomolecular fiber" that can be used to cut through just about everything because it's VERY strong and VERY thin.
The idea even shows up in "The Santa Clause" when the elves free Santa (Tim Allen) by using tinsel to cut the hinges on a jail cell.
Help people in third-world countries! Give them TV's!
And satellite descramblers too!
We got a chance to chat with Michael Laine of LiftPort at this year's National Space Society annual meeting just a couple of weeks ago. They're looking for small investors already - talk to them if you would like to be involved at all. They will also have a private venture funding round coming up for larger investors, but anybody with a few hundred dollars could get involved at this stage (I think the deadline is June 20).
Energy: time to change the picture.
What will be some of the first applications?
I would think in sports equipment as undoubtedly there are many who would pay exorbant amount for an edge.
Imagine the usual enhancements to golf clubs, tennis rackets, etc.
Of course, there will be the downside of new technology when the first major leaguer is suspended for having a nanotubed bat.
Well, there's spam egg sausage and spam, that's not got much spam in it.
...when you can use the indestructible metal Adamantium!
I mean, isn't that the REALLY important aspect of this discovery. Carbon nano-tube cloth woven into a super-thin layer of hypo-allergenic substance. Smooth, silky, unbreakable, conducts heat, you won't know it's there. :-D
Damn, I'm running down to the patent office with this one.
... at the America's Cup yacht racing (http://americascup.yahoo.com/) where cutting edge technology is always on display (http://www.cawthron.org.nz/Assets/cawlec98.PDF). Goodbye spectra (http://www.spectrafiber.com/), hello "carbonanoline" or whatever.
"Consensus" in science is _always_ a political construct.
A lot of people might think I am crazy (I do) but would this material make it possible to build a space elevator? I'm not talking about a building from earth to space, but more a balanced, free-floating structure from the height limit of conventional aircraft into space. This could eliminate the need for rockets as their job could be done by standard jets, with it then joining onto the elevator and unloading the personnel/cargo.
I think, several challenges to just materials science has to be overcome.
For example, our current science in engineering, relies on models and previous engineering attempts, to build new structures.
If you want to build a structure, say taller than the sears towers for example, you can do so, by using the Sears Towers as a reference, then building perhaps 10-15% taller.
Historically, we buld a large number of structures, not just buildings, a little bigger at a time. We build planes, a little faster at a time.
That is how our engineering science works. Even when we sent men to the moon, as colossal a task as that was, we took very small steps at a time, and it took decades.
Building something like a Space elevator, in the timeframe (10-20 years) I think is ridiculous given our current engineering science and application of Mathematics/Statics etc.
Just because you have a material than can go hundreds of miles straight up doesn't mean your structure will.
Whole new branches of engineering will have to be invented, as well as new mathematics to make this structure work.
Personally I think the work Stephen Wolfram has done so far in FSM's (Finite State Machines), may offer a clue as to how we can take much bigger steps in the sciences, with much more predictability, in our models, and methods of construction, to make a space Elevator possible.
At the very least his work sheds light on the principles of complexity, and why we take baby steps in everything we do.
Specifically, how can we design systems, when we have no working model, and to build such a model requires an order of magnitude in scale our engineering science, historically, has never had to deal with.
I think, after a century or more of using this material in terrestrial structures, to understand how it works better, we can start thinking about such an elevator system.
But I think it is a safe bet you are not going to live to see one anytime soon, much to the contrary some of these guys at the Space Elevator web site will have you believe.
-Hack
Got Geometrodynamics? Awe, too hard to figure out? Too bad.