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Researchers Spin Carbon Nanotubes Into Usable Fibers

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wvbraun

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Link<br /><br /><i>Materials scientists from the University of Pennsylvania and chemists from Rice University report the first large-scale manufacture of fibers composed solely of single-walled carbon nanotubes (SWNTs) in the Sept. 3 issue of the journal Science.<br /><br />This new material is a macroscopic realization of many of the amazing mechanical, electrical and thermal properties of nano-scale ideal nanotubes.<br /><br />"Throughout the relatively brief history of carbon nanotube research, the creation of a usable nanotube fiber has been one of the ultimate goals," said John E. Fischer, co-author of the study and professor of Materials Science and Engineering in Penn's School of Engineering and Applied Sciences.<br /><br />"Its applications are nearly limitless, from replacing copper wiring to creating super-strong fabrics to, as some have suggested, building the cable tethers that will allow space elevators to travel from the earth to orbit."</i><br /><br /><br />If progress continues at this rate I think we will have the material required to build a space elevator within 10 years. I can't wait!
 
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arobie

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Very Interesting. It's nice to know that progress is being made with carbon nano-tubes. Thank You.
 
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bobvanx

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Space tethers herre we come!<br /><br />I stumbled across a critique of the phrase "Space Elevator" which pointed out that it's more similar to a pendulum than an elevator. Masses accelerating out to GEO have to pick up the same huge deltaV as a rocket launch, and that energy has to come from somewhere.<br /><br />So I was wondering if that problem of the horizontal, corriolis acceleration had been solved?
 
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nacnud

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The energy comes from the earths rotation. <br /><br />From ISR space elevator FAQ<br /><br /><font color="yellow">What about conservation of angular momentum?<br /><br /> When an elevator ascends the ribbon, it must be accelerated eastward because the Earth's rotation represents a larger eastward velocity the higher you go. The required eastward force on the ascending elevator would have to be provided by a corresponding westward force on the ribbon.<br /> If you go through the math quantitatively, the angular momentum for the climbers requires a pound or so of force over the one-week travel time, and we do that easily with our many tons of material in the anchor and the counterweight.<br /><br /> The quantities really are tiny, but just to be complete, a climber going up pushes the entire elevator slightly to the east, causing it to lean. However, the ribbon recovers for the same reason that it stays up in the first place. Centripetal acceleration is acting on the upper two-thirds pulling it outward, and the lost angular momentum is replaced very quickly (essentially as fast as it is lost). The ribbon will never lose enough angular momentum to even deflect a single degree, let alone fall. The extra angular momentum is stolen from the Earth's rotation.</font>/safety_wrapper>
 
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exoscientist

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The link doesn't tell the nanotubes length only their diameter. We'll need nanotube strands kilometers long in order to make the space elevator.<br /><br /> Bob C. <div class="Discussion_UserSignature"> </div>
 
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thinice

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We'll need long and <i>strong</i> nanotube strands. They might turn out to be as weak as cotton threads, who knows...
 
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bobvanx

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The centripetal force acting on the tether comes from the earth's rotation, sure. That's what holds it up. <br /><br />Look, the deltaV from Earth's surface to GEO is (correct me if I'm wrong) 15 km/sec. Currently we accomplish this with a big rocket and a couple of engine firings, with forces in the range of 3G to 6G, over the span of a few tens of minutes.<br /><br />A payload on a tether still has to accelerate to GEO speed. So you still have to come up with 15 km/sec of acceleration. Give yourself a week (oh-oh, here come my crappy math skills) and it's going to be on the order of .03m/sec^2 that you've got to come up with (I'm sure the real number varies with altitude, but the formula for that is beyond me right now).<br /><br />3cm per second per second doesn't sound like much acceleration, since G is 980cm/sec^2. Hm, it looks like the tether payload experiences a lateral G force of 0.003G for a week long trip. That's 168 hours of a small push along a dynamic system. Anyone remember vectors? How much force is transmitted to the ends of an anchored chain, if you apply a force in the middle? Even a pound of force, over a long distance, can yield tons of force at the anchors. Try it yourself, with 30' of steel cable (even 3/16" diameter will do) and just try to pull it perfectly straight, parallel to the ground. Unless you are Superman, just the weight of that cable will make it so you have to pull with over 500 lbs of force to make it look straight. Add a little more weight in the middle, and you'll double the effort it takes to keep it straight.<br /><br />I wonder what a finite element analysis animation of the whole thing looks like.
 
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Aetius

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What I'm really looking forward to, near term, is the solar sail vehicles we could build incorporating these nanotubes in the sail fabric.
 
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mcbethcg

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It might seem obvious to space nuts that since nanotubes are needed for a space elevator, that is what they will be used for.<br /><br />But nanotubes will also be used for a million other things, in composite materials to make bullet proof vests, car bodies, bicycle frames, tank armour, industrial cables, roof shingles, kitchen sinks, etc.<br /><br />Supply and demand will make carbon nanotubes incredibly expensive for many years to come, just as kevlar are expensive today.<br /><br />We won't be able to afford a space elevator for a hundred years.
 
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arobie

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<font color="yellow">"We won't be able to afford a space elevator for a hundred years."</font><br /><br />I challenge you on that. <br /><br />If by "we" you mean "Nasa", then you might possibly be right, but we (the human race) are not totally dependant on big national gummit programs for space advances any more. (Remember the new space age has begun an it includes private industry.<img src="/images/icons/smile.gif" />) All we need are a couple of rich private investors who are willing to support the space elevator, and there's the money. <br /><br />With this new contest to built components for the space elevator, and even build a prototype space elevator, the elevator will become a concrete concept and will get publicity. Investors will definitely be attracted. We won't have to wait one-hundred years for a space elevator to be built, not with private industry.<br /><br />Here's a link to the thread discussing the space elevator contest if you're interested.
 
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toothferry

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<img src="/images/icons/smile.gif" /> we're another step closer to being able to build a space elavator. <br /><br />The link at the top of the tread also points out other charactoristics of the carbon nanotube. They potentially conduct electricity better than copper and heat better than diamonds. This could be what our future powerlines are costructed... and the bottom of our stove top skillets too.
 
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spacester

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Nice link, the last paragraph caught my attention. <br />"In the meantime, other applications are further along and will hopefully maintain the level of interest and excitement in this fascinating new class of materials."<br /><br />I think he’s talking about the process where you go straight from synthesis to fiber out of a furnace. That’s still the best prospect I’ve seen as a manufacturing process.<br /><br />But what Fischer’s group seems to have contributed is ability to form <i>pure</i> single wall Nanotubes. So you combine the two processes, and . . . <br />*<br />bobvanx, nice math skills! The short answer I believe is that the elevator only needs to be pretty darn straight. It’s known there will be a kink in it at the climber, right? If no climber then it will be a long catenary curve.<br /><br />Nice post Arobie! Well said.<br /> <div class="Discussion_UserSignature"> </div>
 
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halman

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Arobie,<br /><br />It is one thing to be able to design a device or a tool, it is entirely another to have the ability to build it.<br /><br />I have read that Leanardo De Vinci had a design for a helicoptor that was fundamentally sound. However, there was no source of power available until the mid-20th century.<br /><br />Carbon nanotube technology is struggling to create pure nanotubes. It can be done, but it is still an experimental process. A space elevator will need a single fiber thosuands of kilometers long. There is a strong possibility that manufacturing such a fiber will have to be done off-planet, to avoid gravity disturbing the materials molecular distribution.<br /><br />Even if such fibers can be produced on Earth, it is unlikely that the resources would be devoted to such a project until there is a demonstrated demand for a project which will probably be the largest single engineering task the human race has ever undertaken. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>
 
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scottb50

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If you look at cotton, wool or hemp the individual fibers are rather short, but a spool of cotton thread can be infinitely long. I don't think it is a matter of having a single piece or Carbon nanotubes miles and miles long but combining many smaller pieces to make a longer structure. If you use a single strand for the entire length of your cable it's failure is a lot more serious than if you use thousands of smaller strands and one or two break.<br /><br />The problem I see with Carbon Nanotubes is the strength without a resin outer coating. Like fiberglass, the fibers seem to be pretty weak, the resin provides the stiffness but in a cable you have to have flexibility, resin would crack. <div class="Discussion_UserSignature"> </div>
 
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