The World's Longest Carbon Nanotube

Roland Piquepaille writes "As you probably know, carbon nanotubes have very interesting mechanical, electrical and optical properties. The problem, currently, is that they're too small (relatively speaking) to be of much use. Now, researchers at the University of Cincinnati (UC) have developed a process to build extremely long aligned carbon nanotube arrays. They've been able to produce 18-mm-long carbon nanotubes which might be spun into nanofibers. Such electrically conductive fibers could one day replace copper wires. The researchers say their nanofibers could be used for applications such as nanomedicine, aerospace and electronics."

Comments

Wow

[jswigart]

So perhaps the internet will indeed become a series of tubes?

Re:Wow

[Jeff DeMaagd]

Maybe. Maybe in an odd twist, the Internet might actually become a large fleet of nano-trucks.

Re:Wow

[ScrewMaster]

That's a scary thought ... Ted Stevens actually being prophetic, rather than just wrong.

Re:Wow

[Reality Master 101]

Ted Stevens actually being prophetic, rather than just wrong.

You know, Stevens gets a totally bad rap on that whole thing. Exactly what is wrong with that analogy? Even UNIX uses the analogy with pipes; Ritchie* could have just easily called them tubes rather than pipes. And yes, the "tubes" of the Internet CAN get clogged up if there's too much flowing through them.

I've never understood why he took such a beating about it. I guess some people are just determined to believe the worst about people, as though the guy though the Internet was literally air-filled tubes.

Re:Wow

[espressojim]

Maybe this is why? Even if the metaphor isn't horrible, the delivery was:

Ten movies streaming across that, that Internet, and what happens to your own personal Internet? I just the other day got... an Internet was sent by my staff at 10 o'clock in the morning on Friday, I got it yesterday. Why? Because it got tangled up with all these things going on the Internet commercially.

[...] They want to deliver vast amounts of information over the Internet. And again, the Internet is not something you just dump something on. It's not a big truck. It's a series of tubes. And if you don't understand those tubes can be filled and if they are filled, when you put your message in, it gets in line and it's going to be delayed by anyone that puts into that tube enormous amounts of material, enormous amounts of material.

From wikipedia.

Re:Wow

[Wandering Wombat]

I remixed a remix, and it was back to normal... so to speak.

Re:Wow

[Anonymous Coward]

Exactly what is wrong with that analogy?

The context it was said in, he did not say "The Internet is a worldwide, publicly accessible network of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP) [Wikipedia]... You can think of it as a series of tubes...".

Here's a clip with interesting parts from his speech.

I'm also sure you can find the whole thing in the related clips pane. Listen to it (again?) and judge for yourself if he knows what he's talking about

I've never understood why he took such a beating about it

I believe the beating was NOT because he doesn't understand "what the internet is" (that's not a crime, last time I checked), but the fact that he's a legislator working on something that he does not understand at all.

And of course this generation likes bashing on older people because they don't know that the next generation will mock them just the same...

Re:Wow

[ResidntGeek]

When the tubes of the internet get clogged, it's not because of the tubes, it's because of the machines at the end. When tubes are clogged due to too much toilet paper passing through, you have to dig up the tubes and replace them. When a fiber-optic cable is clogged due to too many movies, you put faster routers at the ends - not at all like digging up a cable network all over the world. That's the problem with the analogy, it broke down *exactly* at the place he invented it for.

Re:Wow

[iminplaya]

Ritchie* could have just easily called them tubes rather than pipes.

Whatever happened to just calling them wires? I mean, like, DUUUH!

Re:Wow

[compro01]

Whatever happened to just calling them wires?

that died when the wires became optical fibres.

Re:Wow

[Burpmaster]

The analogy isn't too terrible. It conveys the notion that Internet bandwidth is a shared resource. However, Ted Stevens demonstrated very clearly that he has no idea what he's talking about. He seems to think that when somebody downloads a movie, the entire movie gets put into the 'tube' and all other data gets in line behind it. He thinks an e-mail he got several days after it was sent arrived late because too many movies were coming through the tubes. Not only that, but he referred to the e-mail as "an internet."

He doesn't realize that data is divided into packets, where a limited amount are in transit at one time for each transfer. This fact is very important. It means that bandwidth is shared roughly evenly between all the users of a 'tube' at any given moment, and that e-mails can always be delivered just a quickly as a few packets of a movie would be delivered. His e-mail could only have been delayed by a messed up mailserver, but he didn't know enough about the Internet to realize that.

Re:Wow

[7Prime]

I'm from Alaska. I fucking hate Ted Stevens, I think he's a jerk, and I disagree with about 95% of his politics. But an idiot he is most definitely not. He knew exactly what he was talking about... which actually worries me a lot more than if he didn't. He was attempting to explain it in layman's terms to a bunch of people, who, honestly, were a lot stupider than him. He has a tendancy to over-dumb-down statements like this.

I think its kinda dangerous to assume that he's stupid, because you fail to realize just how much of a cold, calculating demon he is. Believe me, I know people who used to be former interns of his... they're all hoping he'll die soon, but from what I've heard, his physical health is like that of a 30-year old.

Oh well, as long as his party doesn't get control back, we should be relatively safe.

Re:Wow

[hey!]

The proof of the pudding is in the eating.

The proof of the analogy is in the reasoning. Senator Stevens, if you recall, was blaming net neutrality for the fact that his email sent by one of his staff on Friday morning didn't arrive in his inbox until the following Sunday morning.

So, yes, I think Senator Stevens deserves a round of jeers on this one. He's obviously bought a load of tosh about how net neutrality hurts users.

In any case, the correct analogy would be: "The Internet is a NETWORK of tubes." This would lead to more correct reasoning. Since the Internet is a network of tubes, if one tube is blocked up, then stuff just flows through a different path. If email don't make it to me in time, it's because there is a screwup at an end point in the network, since blockages in the middle don't delay things much, if at all. This means I should talk to the persons who manage my email server or who manage the specific tube that links that server to the broader network of tubes.

Re:Wow

[Prof.Phreak]

I guess some people are just determined to believe the worst about people

``Think the worst about people, and you'll usually be right.'' --Catbert.

One nanotube: two birds

[ian_mackereth]

So, not only will we get light, cheap, immensely strong conductors, we'll also have a good market-driven reason to get all that valuable carbon out of the atmosphere!

Voila! No more global warming!

8-)}

Re:One nanotube: two birds

[Dr. Eggman]

But then we'll go too far, we'll continue to make longer and longer nanotubes, until one day we will make a nanotube so long it will destroy us all!

Re:One nanotube: two birds

[iminplaya]

Yeah but, then we'd take it all out, and we would freeze.

Re:One nanotube: two birds

[Meadowhog]

I'm going to pollute my way to a faster connection!
--
CashCrate: Earn money for filling out surveys/forms, real info not required

Come again

[Anonymous Coward]

"Extremely long"?

Perhaps 18 mm stands for... 18 million miles?

Re:Come again

[Anonymous Coward]

Perhaps 18 mm stands for... 18 million miles?

18mm is extremely long for most nerds

Re:Come again

[antron-jedi]

poned

Re:Come again

[ian_mackereth]

Just to get some perspective on this, 18mm is about a third of the length of good quality wool fibres.

That puts it in the area of useable length for macro-sized application.

Re:Come again

[evanbd]

Well, they're still more slippery than wool, so that problem has to be solved too. But this is one piece of the puzzle, and it's very cool to see it coming along.

Re:Come again

[jibjibjib]

You misspelt "pwned."

Re:Come again

[miro f]

wait, so you're saying, the ultimate goal is to be making jumpers and socks out of carbon nanotubes?

Re:Come again

[Wandering Wombat]

You misspelled "I'm illiterate."

Re:Come again

[megamike23]

you know that nanotubes are usually on the order of 10-100 nanometers wide, which is 10-100*10^-9 meters, so 18mm would be 18*10^-3 - 6 orders of magnitude difference

Re:Come again

[electrosoccertux]

Just to get some perspective on this, 18mm is about a third of the length of good quality wool fibres.

That puts it in the area of useable length for macro-sized application.

IIRC when Popular Mechanics discussed these nanotubes for building our space elevator, one of the technical hurdles they mentioned was needing nanotubes ~18" in length for the structure to be sound.

Obviously we've got a long ways to go then.

The other thing they mentioned was that given a mathematically perfect carbon nanotube structure, the highest building we could build before it would collapse on itself is something like 90 miles; and we need

Of course both of these are hearsay so take them with a grain of salt, but the important thing I remember is that whatever the max height of a carbon nanotube structure that we could build is, the height required for a space elevator/cable is several orders of magnitude greater.

So why were we funding this stuff again?

Re:Come again

[imsabbel]

Its about 10000 times longer than what you get when you buy single walled carbon nanotubes at a chemical supplier, like alfa aesar.

Thats hardly something to sneeze about.

They are long enough to, for example, actually connect two macroscopic devices, for example two dies on a MCM.

Re:Come again

[catprog]

What about a rope supported from the top.

Re:Come again

[electrosoccertux]

What about a rope supported from the top. Yes the figure that referenced as to how high we needed the carbon nanotubes to be able to support themselves structure wise was the number that was "several orders of magnitude" (~3 I seem to recall) higher than what the what the mathematically perfect nanotube structure could reach. That height that we needed the nanotubes to be able to reach structure wise was just as you say-- only far enough so that the rest of the tether could act as a counterbalance to the part of the tether closer to earth.

All in all their estimate of likelyhood was "50-100 years in the future" and to not get too excited about it given the technical hurdles to overcome (not just getting it high enough, but dealing with the vibrations such a long cable would experience, for example; or if we wanted to anchor it to an asteroid we have to get ourselves an asteroid first).

Re:Come again

[gringer]

you misspelt "pond"

Re:Come again

[7Prime]

Let me just put on this nice comfy pair of carbon-nano-tube boxers, before you shoot me in the crotch.

See... the bullet just bounced off... "balls of steel," I tell ya!

Re:Come again

[PatrickThomson]

Point is, if they can go from the old-fashioned mess of nanometer-length tube fragments up to 18mm, that's 6 orders of magnitude longer. I know that blithely scaling up science is a major flaw of reporters, but I think there'll come a day when you can just grow a single tube a mile long, and weave them together like the core of a modern climbing rope (but obviously less stretchy).

Re:Come again

[EinZweiDrei]

Thats hardly something to sneeze about.

Except when inhaled.

Re:Come again

[agrippa_cash]

But if your assailant took a flash photo, your pants would catch fire.

Re:Come again

[Eivind]

Doesn't matter much. Once the tubes are long enough that they can be weaved or epoxied and they'll break before they slip, there's little added advantage from having the things be even longer.

If a weave of 10cm long fibres of some material is already failing by fibres breaking rather than fibres slipping, there's not much to be had from the fibres being instead 1 meter or 10 meter long individually.

I'm certain that 18mm long nanotubes are already long enough that a rope made of such would have 90%+ of the strength of a rope made of infinitely long nanotubes.

Re:Come again

[PatrickThomson]

You sound like you know your rope, and I don't, so by no means do I think this is right, but ...

When a traditional fiber breaks, it's slipping on a molecular level. With macroscale nanotubes, the breakage would be right down at the covalent bond level, theoretically giving it a tensile strength on the same order as a perfect diamond. Admittedly, I don't know if that's any good or not.

Re:Come again

[Eivind]

True, a carbon nanotube only breaks when the actual molecule breaks. True, this give humongous tensile strength.

Strengths in the 60 - 100 GPa-range have been measured, which is fairly impressive when you consider that high-tensile steel tops out around 1.2 so basically, a carbon nanotube-rope of a given thickness should be able to hold 50-90 times the load that a similarily thick steel-cable can hold.

But it gets better; carbon nanotubes are (unlike steel) ligthweigth. Often, strength in relation to thickness ain't what counts, but instead strength in relation to weight. Carbon nanotubes have been measured at around 50000 kNm/kg Which mean that if you make a carbon nanotube-rope that is 1m long, and weighs 1kg, then it will be capable of withstanding a force of around 50.000kN. This number is to large to grasp. So, let me scale it for you. It means that a carbon nanotube-rope that is 1 mile long and weighs a single kilo will hold a hummer. (aproximately)

This compares *rather* favourably to high-tensile steel at 155kN m/kg infact it is 300 times stronger.

I guess its no overstatement to say that this is, indeed, "rather good"

Re:Come again

[dcmeserve]

given a mathematically perfect carbon nanotube structure, the highest building we could build before it would collapse on itself is something like 90 miles... ..the height required for a space elevator/cable is several orders of magnitude greater

Carbon nanotubes have their strength in tension, not compression.

A self-supporting building based on nanotubes would have to be a tensegrity structure of some kind, where you'd have nanotubes pulling against something else that's relatively incompressible; maybe a diamond lattice. The tensions involved at the base of such a structure would be immense to keep the thing rigid enough to remain standing.

A space elevator, on the other hand, would rely purely on tension; the centrifugal effects of following the Earth's rotation are what keep it aloft -- that's the beauty of it. The tension forces -- greatest just below the geostationary orbit height -- would be large, but perhaps not as large as in the tensegrity structure.

So why were we funding this stuff again?

You call this funding?

Re:Come again

[Eivind]

Oh, and incase you still don't get what all the "fuzz" is about, here's one more property to make you drool over nanotubes;

They conduct heat along their length *insanely* well.

If you take a square-meter of meter-thick copper and heat one side of the block so that it is 1 degree C (or K, same thing in this case) warmer than the other side, then 385W of power leaks through. A lot. Copper is a good thermal conductor. (as any overclocker would know.)

The same number for a block of tigthly compressed, perfectly aligned nanotubes ? 6000W - 15 times the thermal conductivity of copper (which is already pretty good !)

There's more. Lot's more. Even if just 5% of the potential is unlocked and come into practical use over the next few decades, this is still likely to be one of the most amazing new materials discovered since plastics.

Re:Come again

[Gospodin]

Mr. McGuire: I just want to say one word to you - just one word.
Ben: Yes sir.
Mr. McGuire: Are you listening?
Ben: Yes I am.
Mr. McGuire: 'Nanotubes.'

As Mork would say...

[sycodon]

Nano nano nano.

Re:As Mork would say...

[mark-t]

That's na-NU, my man....

My understanding is that writers originally wrote the it as nano, and so in particular first season merchanise often used that spelling, but Robin Williams pronounced it as nanu.

Re:As Mork would say...

[sycodon]

Yes, but that would not have made much sense in the context of this thread eh? :-)

Re:As Mork would say...

[camperdave]

I'm afraid the only place this conversation would make sense is in alt.tvalien.mork.mork.mork.

Re:As Mork would say...

[Cappy Red]

Isn't that the place where people go to discuss the swedish chef?

Re:As Mork would say...

[Wandering Wombat]

That was actually witty and hilarious. My chef's hat is off to you.

ZOMG BOYKOTT R0L4ND!1!

[pestie]

Did I get it right in the subject line? Apparently all Slashdotters are supposed to hate this Roland guy, right? God, I just want so desperately to be loved...

Re:ZOMG BOYKOTT R0L4ND!1!

[sohare]

You have done your duty well, comrade.

Re:ZOMG BOYKOTT R0L4ND!1!

[ColaMan]

While I don't condone his actions in the past (that is, using /. to push more views to his site for personal gain), he doesn't link-through his site anymore. So now, he's just another submitter of crappy stories that generally give off wildly over-optimistic expectations of future possibilities.

Wee!

[Maekrix]

Yay for buckyballs!

That's what she said

[Syberghost]

(eom)

Re:Now where s my space elevator?

[Anonymous Coward]

18mm? Can be spun together into longer fibers? Get me to space.

Forget space. I just want my flying car they promised me ten years ago.

One more step toward a space elevator?

[SeaDour]

Can these "nanofibers" be used to make a space elevator ribbon? Or does that system require a different method of employing carbon nanotubes?

Re:One more step toward a space elevator?

[QuantumG]

Two points I like to make about the space elevator:

This isn't tomorrow's technology, it is something the human race might do a hundred years from now.

If we have the super strong, super light materials needed to make the space elevator, what else might we do with them? Might we not make better rockets? Or better planes? Might we not make single-stage-to-orbit vehicles which so drastically reduce the price of launch costs that building a space elevator is not only possible, but unnecessary?

Re:One more step toward a space elevator?

[EllisDees]

Those would have to be some *drastically* reduced prices to compete with a space elevator. Accelerating to escape velocity is always going to take a lot of fuel, where with the space elevator it's not even an issue.

Re:One more step toward a space elevator?

[camperdave]

Might we not make single-stage-to-orbit vehicles which so drastically reduce the price of launch costs that building a space elevator is not only possible, but unnecessary?

The problem with rockets has never been the mass of the rocket, but the mass of the fuel. There's only so much oomph you can get out of a million litres of hydrogen and oxygen chemically, and it's only marginally more than the power it takes to lift a million litres off the surface and into space. Sure, a lighter fuel tank, and lighter payload will help, but not significantly.

No, if we want cheap access to space, we either go nuclear, or build some sort of space elevator. While we may just be at the threshold of being able to make materials with the tensile strength needed for a beanstalk, we have the tech to make gas core nuclear rockets right now.

Re:One more step toward a space elevator?

[CrtxReavr]

This isn't tomorrow's technology, it is something the human race might do a hundred years from now.

I think you're wrong about that, as do the people doing most of the research on the subject.

In this discover.com article covering Brad Edwards' NASA-sponsored research into Space Elevator technology, his completed work under a $500,000 NASA research grant reveals the technological and economic feasibility of space elevators.

Re:One more step toward a space elevator?

[evanbd]

It's not about the fuel prices. Never has been, and won't be for the foreseeable future. Propellant is cheap, it's the vehicle that's expensive. Elon Musk of SpaceX was recently quoted as saying propellant costs are comparable to the accounting errors.

Remember that the space elevator has to supply all the energy to the payload too, but it has to get it in a much more expensive form -- like electricity beamed from the ground by lasers or some such. Rockets aren't actually all that energy inefficient in comparison.

I used to be a huge fan of the space elevator idea, but then I started looking what those same materials do to rockets. SSTO is just the start. And remember, those materials will change rockets long before they make a space elevator.

Of course, I am a rocket engineer, so I might be a little biased, but I've also examined the problem in some detail :)

Re:One more step toward a space elevator?

[Hatta]

While we may just be at the threshold of being able to make materials with the tensile strength needed for a beanstalk, we have the tech to make gas core nuclear rockets right now.

Do we have the tech to deal with the fallout of the inevitable accidents?

Re:One more step toward a space elevator?

[TEMMiNK]

The problem being that you put the words Nuclear and Rocket together and the Russians get really nervous, and nobody likes a nervous nuclear power.

Re:One more step toward a space elevator?

[Telvin_3d]

yeah, and 'fallout' is the right choice of word.

Re:One more step toward a space elevator?

[init100]

we have the tech to make gas core nuclear rockets right now.

With nuclear rockets, you would have to solve vast PR problems though. Just consider the demands by the greens to close nuclear power stations, which are firmly on the ground. A nuclear-powered rocket, with the significant risk of an accident and its fuel being released into the environment, could face much more severe problems than nuclear power stations.

Even to me, who is usually pro-nuclear, it isn't clear that nuclear rockets launching from the surface of the earth is a good idea. Considering the history of modern rocketry, we've had quite a number of accidents with ordinary chemical rockets, and it would be naive to assume that accidents wouldn't happen to those nuclear rockets. Nuclear rockets launching from orbit. such as on interplanetary missions, is a very different matter, which is do not oppose at all. There is a problem though: How do we get the nuclear fuel to orbit without the risk of a serious accident?

Re:One more step toward a space elevator?

[tsa]

A space elevator contains so much carben we should build it just to get rid of our pesky global warming problem. Grow plants to take the CO2 out of the air, turn them into space elevator, and Bob's your uncle!

Re:One more step toward a space elevator?

[evanbd]

People don't seem to get this somehow. Yes, mass ratio matters. A lot. Let's look at LOX+Kerosene, a very typical combination in many ways. You get an ISP of about 3000 m/s in a medium-high performance vacuum engine (the case for most of the way to orbit). LEO takes about 9000 m/s of delta-v by the time you account for aerodynamic and gravity losses. That means the mass ratio of your rocket needs to be about e^(9000/3000) = e^3 = 20. So 5% of your rocket makes it to orbit. Yup, that sucks. LOX costs about $0.07/lb in bulk, kerosene about $0.30. So propellant costs are about $0.15/lb for propellant, or $3/lb of orbited mass.

Now lets look at the space elevator. Climbing to geosynchronous orbit is equivalent to about 8000 m/s of delta-v (roughly... don't have the exact number off hand and I don't feel like calculating it). From 1/2M*v^2, that's 32MJ/kg. That's about the energy you get from burning 6 kg of LOX-kerosene. So from an energy equivalence standpoint, you're using 6 kg of propellant worth of energy instead of 19 -- a factor of 3 improvement.

The problem with the space elevator is twofold. First, the required *form* of the energy is different. You can't just use cheap hydrocarbon fuels -- you have to convert it to electricity, and then get that electricity up to the elevator either by beaming it or along wires, and neither option is efficient in the slightest. In fact, by the time you turn the hydrocarbon fuel into electricity and then get it to the elevator car, you're under 50% efficient; being as high as 30% would take a lot of work and be quite impressive. But the rocket was 30% efficient! Space elevators are *not* particularly more efficient than rockets.

The second problem is the infrastructure of the space elevator -- the required capital investment for a certain payload rate (kg delivered per day) is higher than for the rocket (we won't even discuss non-reusable rockets). Even if you got the space elevator more energy-efficient than the rocket, this fact combined with the slower transit time, the geosynchronous orbit as the only one available, and the more complicated technological requirements, the rockets win.

Yes, the space elevator tech is harder. The ribbon itself and the beamed power are the obvious examples, but there are others. For example, the tires on the car that work against the ribbon -- you need tires that run at about Mach 3 and are good for 27000 miles. That's not even remotely easy. You need motors that have higher power to weight ratios than currently exist. Etc, etc, etc. Rockets, in comparison, are easy. Especially if you have space-elevator class building materials available -- at that point you can do SSTO with pressure fed rockets, and get rid of the pumps altogether -- the pumps being the hardest part of rocket engine development by far in a conventional design.

When people say that for space elevators you only have to provide the energy to climb up, and aren't wasting the energy carrying propellant, they often forget that it's actually a *lot* of energy to climb up, and that rockets are actually remarkably good at converting available chemical energy into exhaust kinetic energy -- some are better than 80% efficient by that metric.

Re:One more step toward a space elevator?

[imsabbel]

If you are really a "rocket engineer" (what kind, 4th of july ones?), then you have a really narrow horizon.
Try to imagine how many launches you would need to, for example, build a mining and refining base on an asteroid. 25 million tons, in an escape orbit, anybody?
Thats a 1000 times of all launches in human history, for something that might be just a little thing if we ever go interplanetary.
Try a quick calculation of how it would cost...

You might be thinking in current terms "All we send up is highly technical stuff that costs 50k to produce vs 8k to list, to rocket costs arent the limiting factor", but think about getting bulk material up there...

Re:One more step toward a space elevator?

[catprog]

You do not need to use your electric motor to accelerate to escape velocity. You gain escape velocity by moving along the ribbon and then using the earth's rotation to accelerate. What about using coal for the electricity? Why do the tyres need to run at Mach 3 if you run the climber at say Mach 0.5? For that matter why do you need tyres(look at chair lifts. The wheelhouse at either end)? For power to weight ratios look at the solar planes or solar cars? (You only need a motor that can loft itself for it to work. Economically you would need better though)

Re:One more step toward a space elevator?

[evanbd]

The whole thing is about economics. You want high speed for short transit times, obviously, but the important reason is to get the car off the bottom of the elevator. You need to do this because of the weight limit on your cable. Once the car is a ways up it counts less against the weight limit. This implies high speed tires, high power motors, and high power transmission rates. The reason I say Mach 3 is nothing magic, just that many elevator proponents talk about speeds around 1000 m/s.

Even if your car "only" goes at 100 m/s, that's 1kw of power *per kilogram* of mass (elevator + payload), or about 1/2 HP per pound -- which is close to the weight of current electric motors, let alone the car and payload. The power to weight isn't required to loft the car, it's required to loft it quickly. And don't forget, you have to cool the motor -- a task that gets harder in vacuum.

You still actually need to put a lot of energy into climbing. The first 1000km, where centripetal acceleration isn't helping much and gravity is still high, means about 1E6m * 10 m/s^2 or about 10 MJ/kg. Total energy is well more than that, I think about 30MJ/kg. I don't have the exact number handy, but it's big.

The problem with solar cells and any number of other power technologies is, again, power to weight and therefore elevator car speed.

I'm not trying to say any of this is impossible -- just that the challenges make rockets look really easy, especially if you have space elevator class materials available; and rockets aren't really all that inefficient from an energy standpoint, once sad materials are available to improve the mass ratio a bit.

Re:One more step toward a space elevator?

[richard.cs]

This was pretty much my first thought when I read the summery. IIRC the tensile strength of carbon nanotubes is more than sufficient to make the ribbon but up until now they have all been extremely short and thus difficult to make a ribbon from. I don't have the book on me at the moment so I can't check this figure but I think about 4mm was the point that it started to become feasible.

Re:One more step toward a space elevator?

[Ash Vince]

Your idea of a space elevator is interesting, but very wasteful.

To make a far more energy efficient design you need to run the cars at constant speed. You also need to attach each car together. That way you can use the energy of the cars on the way down to help power the cars on the way up, much more like how a real elevator works. This means that the whole system requires a much more constant energy input.

This also does away with the idea that each car ever stops. It presents a problem of how you load and unload a moving system at the bottom but this is certainly a solvable problem. At the top you just have a fleet of small craft who dock with each car. Everything is moving in space anyway so all you need to do is match velocities, something the shuttle already does with the space station.

The mistake you seem to be making is trying to treat each car as separate entity rather than looking at the system as a whole. If you can do this then you can use the potential energy of the stuff (raw materials, people coming home, etc) you are bringing back rather than wasting it. This is why space elevators have the capability to be far more energy efficient than rockets ever can.

Now before everyone replies with all the problems, I know, its hard. The fact remains however that continuing on the current task of using semi reusable rockets (like the shuttle and it SRB's) then just letting the stuff we want to bring back fall is not an option. It wastes too much energy from the standpoint of bringing materials back.

Once I could have filled my post with numbers too, but I finished Physics (with Space Tech) several years ago now and have forgotten most of the maths needed.

Re:One more step toward a space elevator?

[evanbd]

The curve is exponential -- each incremental delta-v requires exponentially more propellant. But the *point* is cost. I don't care how much fuel it takes, I care what the ticket price is. If you have a spacecraft that's built of unobtanium and weighs nothing, you can solve the exponential problem by just adding more tankage accordingly. At some point conventional chemical rockets stop being the answer because of this exponential growth, but that point is well past just getting to orbit. Interplanetary travel is doable on chemical rockets, but probably not ideal -- ion engines and solar / nuclear thermal rockets probably win for that long term; for interstellar, something entirely different is needed. The point is that for the regime space elevators are relevant, the exponential curve hasn't killed chemical rockets as an option.

Re:One more step toward a space elevator?

[Eivind]

1000m/s vertical speed on the lowest part is a *lot* too much for anything that pulls itself along by the help of friction and electric motors. Perhaps achievable longer-term by some sort of vertical maglev-technology or similar.

In any case, that's not required. It's a long way (36000km) to geosynch, but gravity falls of very rapidly.

If we ignore the contributions of the centripetal force, then gravity scales with the square of the distance. When starting at equator you're about 6500km from the core of the earth. Which means that you need to climb about 2500km before gravity will be half what it was at the start. That'd happen in 20 minutes at your stated speed. You'd need that speed -- if you wanted to launch once an hour, but that's a ridicolously high launch-rate for a first system.

Re:One more step toward a space elevator?

[able1234au]

Is there a reason the space elevator cant draw power from the ground instead of needing solar panels? Ground based power would be the most efficient you would think.

Re:One more step toward a space elevator?

[evanbd]

The elevator car isn't on the ground. You have to get power to it somehow. The basic options are solar generation on the car, beamed power (either laser or microwave... both have problems), or wires (which have resistance problems). So yes, you use ground based power -- the power isn't the problem, it's the power transmission.

Re:One more step toward a space elevator?

[dbIII]

Remember that the space elevator has to supply all the energy to the payload too, but it has to get it in a much more expensive form -- like electricity beamed from the ground by lasers or some such.

I never really understood this bit. There you are with a highly conductive material that will conduct that same as graphite sheets in the high strength direction (which is straight up the wire) and people are talking about broadcast power? Even if it is well columnated not a lot of power is going to hit your dish some huge distance up - and the intensity will create major problems. This is why I keep thinking we are facing a confidence trick like the 1980s plan to build a spaceport in the north of Australia by a two person company.

Re:One more step toward a space elevator?

[evanbd]

The problem is that the wires have resistance. And they're thin -- the elevator is thin. So the resistance is non-trivial. It might be tiny, but it's not zero, and over thousands of kilometers it adds up. It's not impossible, and whether it's better or worse than beamed power depends on who you ask and what assumptions you make -- ie if you can get ballistic conduction working for that length of nanotube. Also, it needs to be at very high voltage (to keep the current and I^2*R losses low), which makes the power conversion to run the motors harder (read: heavier and less efficient; doing it is straightforward enough). My personal guess is that the wires beat the lasers, but I think I'm in a minority there.

Re:Nano* is cool!

[corsec67]

And you miss the obvious?

You do that while listening to your Nano? (Ipod Nano, that is)

Carbon fibre

[TapeCutter]

Apart from more tubes for the interwebs, I would imagine that 18mm is also long enough to make carbon fibre products that are lighter and stronger than what is currently available. I wonder if an America's Cup or F1 winner will one day be built from nanotubes?

Re:Carbon fibre

[evanbd]

Note that nanotubes != CF.

That said, people are already starting to incorporate nanotubes in composite materials. The two hard parts are that they're really slippery and it's hard to get the matrix to stick to them, and that they tend to clump up a lot. The increased length helps with the first problem -- slippery is less of a problem if there's more surface to stick to. I don't know about the dispersion.

Nanotube composites are already impressive. You can get things with 30-50% more stiffness, 50-200% more thermal conductivity, lower thermal expansion, and other useful properties. Metal matrix composites are also impressive. Think aluminum with nanotubes added. You can get double the strength, more than double the stiffness, and double or more the thermal conductivity in something as machinable as aluminum by adding only 1-2% nanotubes. This is a *rapidly* advancing field, and it's poised to seriously change high end materials science in the very near future.

Re:Carbon fibre

[RealGrouchy]

I wonder if an America's Cup or F1 winner will one day be built from nanotubes?

I think they'll still be made of skin and bones for quite some time.

- RG>

Re:Carbon fibre

[samkass]

Isn't carbon fiber that's microscopic in one dimension but macroscopic in the other the whole reason asbestos and other mesothelioma-causing "breathable" carbon structures banned? Is this just a way to manufacture lung cancer, or is there something about nanotubes that makes it not do the same thing asbestos does to the lungs?

18 mm... Great!

[camperdave]

18 millimetres? Great, only 99,999.999982 km to go!

Re:18 mm... Great!

[Snarfangel]

Perhaps it'll be like Moore's law. If the length doubles every 18 months, it'll less than half a century.

Re:Now where s my space elevator?

[QuantumG]

You are aware that the space elevator is for sending cargo into space right? And the cost of building a space elevator is never amortised into the cost per kg when people are making claims about how much cheaper the space elevator is over rockets.. and have you ever noticed how they always seem to compare the cost of launching cargo on a space elevator built from super strong materials to rockets that are built from today's materials?

The economics of space travel has very little to do with the technology we use to get there, and more to do with the demand for launches.

My microtube is bigger than your nanotube

[mrbluze]

... do you think they could be compensating for something?

World's Tallest Midget

[Luyseyal]

In other news, Bjorn Stevens, world's tallest midget, and jumbo shrimp decry military intelligence in Iraq peace action.

-l

Re:World's Tallest Midget

[tmosley]

Thunderous silence as /. does not undertand oxymorons.

Great...

[DoofusOfDeath]

Now we're going to get spam advertising ways to lengthen our nanotubes...

The real killer commercial application

[mad zambian]

will be when someone figures out how to either join these fibres together, or grow a continuous nano-scale monofilament.
Then we will really see what Arthur C was talking about.
The applications for "diamond" fibre are enormous.

some perspective

[Goldsmith]

Although the PR person who wrote this obviously thinks this is a major breakthrough, these guys are using a method which was originally invented by Japanese researchers three years ago (google for "CNT super growth"). The Japanese guys have since focused on getting the fastest growth rate possible (I think it's about 0.2mm/min... if you want to figure out how many, many years it would take to grow a space elevator). There are lots of people working on improving this growth method, 18mm arrays may be the longest, but it seems to be in the same range as other people working on the "super growth" method. That doesn't diminish this research, rather it means that this method is very likely to work in the long run for industrial scale growth of nanotubes for materials (more simply, it's easily reproducible, and people want "nano-enhanced" golf clubs).

Isolated nanotubes have been grown longer than this (I've grown isolated nanotubes longer than this, and I'm not a growth specialist), as have bundles of nanotubes. This is the longest array of pure, aligned, continuous nanotubes.

Re:some perspective

[khallow]

What makes it not a major breakthrough? One of the problems with carbon nanotubes is that they don't adhere well to a resin matrix. A propose solution was to make really long nanotubes. 18 mm is really long. If they can make it in bulk, then they can make, for example, the space elevator tether. Even 0.2 mm/min is a sufficient growth rate if you're making enough (in orders of magnitude) carbon nanotubes at a time.

Re:some perspective

[Goldsmith]

If no one could make really long nanotubes, yeah it would be amazing, but arrays like this are routinely made several millimeters in length, and some people make single nanotubes ~150 mm long.

The technology does not yet exist to piece together nanotubes strongly enough to make a space elevator... which is why I was careful to use the word "grow." If one could piece nanotubes together well enough, then everything does get much easier.

Re:some perspective

[khallow]

I guess I don't see the problem. Are there quality control problems with these lengths (eg, many flaws for the length)? They seem sufficiently long even with a weakly bonding resin. I don't see the reason one couldn't make an adequate space tether from Earth to past geostationary with these lengths. For example, in the paper, "Direct Spinning of Carbon Nanotube Fibers from Chemical Vapor Deposition Synthesis" by Ya-Li Li, Ian A. Kinloch, Alan H. Windle, they claim to (among other things) spin a thread with mostly 30nm single-walled nanotubes with an aspect ratio of ~1000. That means that the individual fibers were around 0.03 mm in length (if I understand the meaning of aspect ratio correctly). Tensile strength was somewhere around 0.1 to 1 GPa, far shy of the space tether's need for tensile strength of 65-120 GPa with density of graphite. The current fibers are about 600 times the length and as I understand it, the key constraint with the spun fibres was the weak binding between adjacent nanotubes. A length 600 times longer should naively have 600 times the binding energy between nanotubes (somewhere around 60-600 GPa compared to the nanotubes' tensile strength of up to 120 GPa). So that sounds to me like a thread spun with these far longer tubes will instead be limited by the strength of the nanotubes rather than how well they stick to each other. And that there is little benefit to creating even longer nanotubes.

Re:some perspective

[Goldsmith]

I see where you're going with that, but the intertube tensile strength doesn't scale with length. Binding energy is different from tensile strength. The work which you're doing in pulling apart nanotubes depends on how the binding energy changes with time, not so much on the total energy. If you pull a 100nm section of a nanotube out of a bundle, you could think of it costing the entire binding energy, but then you get back 100nm less than the starting binding energy when you stop So the end cost of that slippage in terms of energy is very small. You could think of breaking this down to pulling the tube out atom by atom, spending and recieving binding energies as you go. You may worry about initially getting things going, but you don't have to pay that full cost at once, instead stretching a small section of the nanotube to get it started.

In March, there was a good APL which describes how weaving nanotubes together gets you to a maximum intertube tensile strength of 1.5 GPa, and there are lots of older APLs on this subject as well.

Re:some perspective

[khallow]

Drat, I see your point. You might be able to get top performance if the structure isn't loaded normally, but doesn't seem viable for cables under heavy loads for years at a time.

Re:Now where s my space elevator?

[confused one]

It's quite a stretch to go from 18mm to geo-sync orbit, isn't it?!

a clarification

[Anonymous Coward]

This is not the record for longest tube ever grown. Groups have grown single tubes the size of their substrate wafers (4 inches usually). This group grew a long bundle of CNTs. In the field we call these 'forests'--imagine a lawn, but at the nanoscale. The blades of grass are the CNTs poking up off the surface.

Remember also that the figure of merit of a CNT when used for its mechanical properties is the growth defect density per meter, and even for the best growth techniques so far this ends up being a number like 1 every 10 microns (10^-6 m).

This means that for something such as a macroscopic cord, not only would one have to grow incredibly long CNTs, they would also have to be nearly defect-free in order to satisfy the (nearly magical) strength requirements attributed to them by many people.

Tag: Biotech

[0123456789]

I don't normally complain about mods/tags etc (seems a bit pedantic), but how did this get tagged as 'biotech'?

Is the word 'carbon' enough to be classified as 'biotech'? Is a pencil 'biotech' now?

RTFA

[Raynor]

It would be nice if people actually read up the subject before posting this garbage...

This is not "The World's Longest Carbon Nanotubes." It's the longest mass-producable parallel carbon nanotubes.

Great...

[LynnwoodRooster]

Now some Inanimate Carbon Tube will win Employee of the Week before I do...

H. J. Simpson

Million times longer than they are wide

[Hittite Creosote]

It's a relative term - extremely long compared to their diameter. These are about a million times longer than they are wide.

Re:Now where s my space elevator?

[MikShapi]

It's also a stretch to go from a very big barrel of hydrogen to GEO, and yet it's been proven to get payloads there.

There's nothing particularly revolutionary about any of the physics underlying the SE. Once a point (that is not moving further and further away) of tensile strength (in polymer fabric you can weave, not in the individual material you build it from) is reached, you build it. Period.

If you can make fibers that behave more like thread and less like sand pebbles, you can load more into the fabric, and the strength of the available fabric (per given weight) rises a notch higher.

At some point, it'll reach the elevator-capable point.

Space Elevator Progress Report anyone?

[MikShapi]

Here's what I remember from last time...

To be held up, a space elevator needs a FABRIC with a tensile strength of about 65GPa.
To build it, you'd want a safety factor of about two, thereby a tensile strength of about 120-130GPa.

I do not know the specs of the tubes from TFA, however

Very short INDIVIDUAL single-walled carbon nanotubes have been created (in a lab, in small quantities, using processes that may be prohibitively expensive) with measured individual fiber strength of about 60GPA.
"Very long" ones were (previously) created at about 1cm with substantially lower tensile strength (circa 4GPA if memory serves me right).
The last several years were spent by industry leaders in this field ramping up production of CNI by several orders of magnitude, whereas bulk availability made prices of CNI go down orders of magnitude.

Existing processes of weaving tubes into a fabric involve loading the fabric with ~5+% of CNI. The last Elevator2010 competition saw competition tethers in the 4GPA ballpark (using fibers in the 30-60GPa ballpark I'm guessing), none of which could beat the commercially-available "house tether".

This is all layman talk of an enthusiast, not a professional. I'm a coder/syadmin gone biochem, not an engineer. If someone a bit less clueless than me can correct and/or bring this up to date (some of what I recited here I've acquired ~3 years ago, things would have progressed since then), I think we'd all be the wiser.

Cheers.

Are tubes the next laser?

[RealGrouchy]

Back when lasers were still new, it was really big in sci fi (such as James Bond and Star Trek), as a magical tool with near universal applications and can safe (or destroy) lives.

Nowadays, lasers are. They're used in everyday objects like CD players, to complex medical procedures like laser eye surgery and those machines that kill otherwise inoperable brain tumours.

I have a feeling that carbon nanotubes will too.

- RG>

Re:Spinning into thread

[RicktheBrick]

I hope that they could build a light weight rust prove frame for an automobile. I recently had a 1997 Geo Metro that had the front half of the frame rusted out and the cost of repair was more than the cost of buying another used car. I hope that they can use this to line the tunnels that we could dig underground and that we all than move our home underground.

Energy needed for climbing...

[Joce640k]

they often forget that it's actually a *lot* of energy to climb up

Can't you have a pulley system with two cars - one goes down when the other goes up. That would reduce energy costs to practically zero. All you need to do is fill the one at the top with atmospheric water and it would pull the other car up as it descends.

Re:Energy needed for climbing...

[evanbd]

Atmospheric water? What atmospheric water? You're out of the atmosphere...

This probably works better with a bunch of cars on the cable and wired power transmission; instead of space-elevator length *moving* cables you just need regenerative braking. It helps some, but most payloads probably stay up there, so you only recover the car energy, which is supposed to be a small fraction of the total. The passenger trade will run on rockets, the elevator is for things like satellites, propellant, and other bulk supplies.

Then again, if you're mining asteroids, that's a different matter -- and one of the few truly compelling cases for the elevator concept in my opinion. It neatly solves the power transmission problem on the elevator, and also solves the problem of how you get the asteroid down without bringing it so close to Earth while it's in a single large lethal piece (remember, geosynchronous orbit is actually quite a long way away).

Problem already solved!

[crhylove]

Luckily, yester-year's super gee-whiz invention "The Laser" will do the job nicely.

Can't wait to get a pair of laser-snips.

rhY

It isn't about lifting things into orbit...

[elFisico]

It's all about having a cable going from a place with lots of space and lots of sunlight down to where that power is needed.

IMHO a space tether will mainly solve our energy problem, cheap access to space is only a by-product...

whats the aspect ratio of these long tubes?

[peter303]

Nanometers wide, millimeters long. Isnt that an aspect ratio approaching a million?