Long, Stretchy Carbon Nanotubes Could Make Space Elevators Possible
January 23, 2009 by Lisa Zyga
A space elevator would extend 22,000 miles above the Earth to a station, and then another 40,000 miles to a weighted structure for stability.
(PhysOrg.com) -- Scientists from Cambridge University have developed a light, flexible, and strong type of carbon nanotube material that may bring space elevators closer to reality. Motivated by a $4 million prize from NASA, the scientists found a way to combine multiple separate nanotubes together to form long strands. Until now, carbon nanotubes have been too brittle to be formed into such long pieces.
And a space elevator - if it ever becomes reality - will be quite long. NASA needs about 144,000 miles of nanotube to build one. In theory, a cable would extend 22,000 miles above the Earth to a station, which is the distance at which satellites remain in geostationary orbit. Due to the competing forces of the Earth's gravity and outward centrifugal pull, the elevator station would remain at that distance like a satellite. Then the cable would extend another 40,000 miles into space to a weighted structure for stability. An elevator car would be attached to the nanotube cable and powered into space along the track.
NASA and its partner, the Spaceward Foundation, hope that a space elevator could serve as a cost-effective and relatively clean mode of space transportation. NASA's current shuttle fleet is set to retire in 2010, and the organization doesn't have enough funds to replace it until 2014 at the earliest. To fill the gap, NASA is hiring out shuttles to provide transportation to the International Space Station from private companies.
So NASA could use a space elevator, the sooner the better. Space elevators could lift material at just one-fifth the cost of a rocket, since most of a rocket's energy is used simply to escape Earth's gravity. Not only could a space elevator offer research expeditions for astronauts, the technology could also expand the possibilities for space tourism and even space colonization.
Currently, the Cambridge team can make about 1 gram of the new carbon material per day, which can stretch to 18 miles in length. Alan Windle, professor of materials science at Cambridge, says that industrial-level production would be required to manufacture NASA's request for 144,000 miles of nanotube. Nevertheless, the web-like nanotube material is promising.
"The key thing is that the process essentially makes carbon into smoke, but because the smoke particles are long thin nanotubes, they entangle and hold hands," Windle said. "We are actually making elastic smoke, which we can then wind up into a fiber."
Windle and his colleagues presented their results last month at a conference in Luxembourg, which attracted hundreds of attendees from groups such as NASA and the European Space Agency. John Winter of EuroSpaceward, which organized the conference, thought the new material was a significant step.
"The biggest problem has always been finding a material that is strong enough and lightweight enough to stretch tens of thousands of miles into space," said Winter. "This isn't going to happen probably for the next decade at least, but in theory this is now possible. The advances in materials for the tether are very exciting."
via: Times Online and Gizmodo
© 2009 PhysOrg.com
May 18, 2009 |
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Imagine 35,000 miles of carbon nanotube ribbon falling back down to earth with a huge captured asteroid counterweight falling with it!!
Furthermore most designs for a space elevator involve it being able to move at least slightly to avoid collisions with satellites, and also a no-fly zone around it in which anything will be shot down.
Possibly... depends on how much further out from geosynch orbit the counterweight is and how much tension is on the ribbon. If only enough tension is on the ribbon to be able to lift a few hundred tonnes of mass then a passenger airliner slamming into the ribbon might impart enough force to snap tug the counterweight and all that additional ribbon mass into the earths gravity well..
I say we will never build one as long as kook religious zealots are still killing people over fictitious supernatural beings...
Now perhaps the space elevator idea will be a lot easier to manage on the moon. However, I'm not sure how far off the surface it would have to be to match the moon's slow rotation - perhaps as far as the earth? Perhaps much farther?
So there isn't any danger to these things. Mind you, that doesn't mean we'd want terrorists trying to snap the lines. It would be horribly expensive to re-string the station to Earth again.
I am worried about some of the torques and high-altitude stresses though. AFAIK no one has worked out exactly how strong a cable would have to be to withstand those forces with a decent sized cargo hanging from the line.
Also, since the cable is not in orbit, anything dropped from it won't just float alongside. There will be effective gravity, either real or centrifugal, everywhere except at GEO.
If only there was some kind of aircushion to prevent the wire from reaching dangerous speeds, you know, like a 5 trillion tonne atmosphere or something?
If only the cable could be made out of a thin ribbon of super-hard material that would slice through a plane like butter, you know, like carbon nanotubes?
Oh and the counter-weight will probably be made from yet more carbon nanotube ribbon stretching further into space.
No space elevator. :) Enjoy.
from what i figure, it will take 293 days to create one strand of nanotube 1 mile long at the rate stated in the article. with a total of 62000 miles of nanotube required, it would take about 18,186,666 days to make it. then if you multiply that by the number of strands necessary to support the space elevator, lets say a smaller number, around 50,000 (NO IDEA IF THIS IS EVEN CLOSE TO NUMBER NEEDED, WHETHER < OR >), you get 909,333,333,333 days.
If you see a flaw in my math there, just let me know, I do after all have a few behind me (ok, quite a few). But from I'm figuring at the moment, at the current rate of production, it would take ~2,491,324,201 years to make the nanotube structure alone. The elevator would be dust by then :)
Anyways, assuming my drunken math is around accurate there, then this is simply not realistic, as there is little to no possibility that production of this nanotube will multiply by 2 billion fold to make around a 2 1/2 yr project (unsure of cost effectiveness however so cannot equate that in). Hell, even at making it a 50 yr project...can anyone see production getting that large for nanotubes.
with all that being said, this is a kick a** idea. but i sure as hell would need a stewardess with tons of alcohol on board if the thing ever stalled or broke down.
I would think some sort of controller electromagnestism would be more cost effective, faster, and safer.
also, it may be possible controlled electromagnetism is the plan with the nanotubes being the conduit...no clue...doesn't say in the article either. But if that is the plan, if I had the say so, I'd scrap the hell out of it and user something else, just based on the timeframe I mentioned.
I am certain there are many facts we don't know on this though, so my statements could simply end up being in inaccurate. Right or wrong, at least the answer may be known by someone :)
this article states that is would reduce the cost to orbit by a factor of 5. More like a factor of a 100.
The article doesn't mention the strength of these tubes :(
I think platinum is able to stretch much more than 18 miles per gram.
http://nextbigfut...bes.html
point well given and received :)
trusttheone-
i spoke using numebrs from the lab scale only because it doesnt specify any cost estimates for producing the nanotubes by the gram or by the mile or anything. if its not all that expensive, sure, industrial scale is realistic. chances are though, i bet, that this is a very expensive process to build these, which could make industrialization not really feasible until a more cost effecive method could be found.
our species has accomplished some TREMENDOUS feats...but I am very skeptical that we could, would, or even should build something that is 62000 miles and would likely be prone to many problems.
that would be a site to behold though, the construction of such a thing...imagine riding the elevator up it while you built it.
As for this idea of a 'space elevator', READ the Arthur C. Clarke Novel called 'The Fountains of Paradise' which introduced this subject to the world, in a science backed Sci-Fi novel. Arthur's elevator, was built in Sri Lanka, for the reasons covered here. Arthur covers all of the challenges.
We are ALSO inches away fro Larry Niven's ideas on a thing in his novels he called 'Sinclair Molecule Chain', which is literally the kind of material needed here. Read Some of his works for a in-depth covering of the technical and social/cultural integration of that sort of material.
If someone DOES create such a material- PLEASE have the common sense to be named 'Sinclair', OK?
If the station at the end of the elevator is in geosynchronous orbit and you haul something from the earth's surface to that orbit don't you have to give it (ignoring friction from the atmosphere) exactly the same amount of energy and momentum that you would have to if you launched it? That is the change in potential climbing out of the gravity well and the change in kinetic to orbit the earth once in 24 hours.
Does a space elevator just save you the friction cost (but what is the friction on the cable) and the reusability of the launch vehicle? Of course you could recover energy from things going down and use that to supplement things going up but the whole point is to put more stuff up than comes down.
Has anyone got a pointer to a good paper on the subject? Google is just turning up a lot of articles with no real physics discussion.
As for the counterweight, there are at least three ideas:
1: Extend the cable, and use the extra cable as counterweight mass. This produces the longest elevator, which would be handy for launching interplanetary probes, as a sling. It's also the most expensive in terms of cable cost.
2: Use the construction equipment as the counterweight. Some designs call for sending an initial strand up by rocket, and then adding more with small climbers/cable layers. These could be left at the end as part of the counterweight. This may be the simplest, as it would be quicker than having a single machine climb back down after each strand is added, and less wasteful than simply turning them loose in space.
3: Use a large rock for the counterweight. This would be the ideal solution for a BIG elevator, but the cost of catching a small asteroid for the first, small cable would be prohibitive.
For those who want the math, here is why the actual center of mass is above GEO:
http://gassend.ne...dex.html
I didn't realize that, but with a large counterweight, it makes sense.
For a technical analysis, here is a large PDF file from the Nasa Institute for Advanced Concepts. It's 80 pages, 15.36MB, and may take a while to load on a slow connection:
http://www.niac.u...ards.pdf
It does have some VERY technical formulas, still but makes for interesting reading.
Of course, space terrorists wouldn't necessarily need a space elevator to wreak havoc on Earth. They could just lob a few hundred iron-based asteroids at us, and maybe we could deflect them all in time or maybe we couldn't. Or they could use a rail gun or a laser. The possibilities are limitless, and unfortunately our offensive technology seems to be outpacing the defensive. (We still have no technological defense against your basic nuclear bomb!)
This would let you fly people and cargo to space in a small ship with far less fuel weight except for the occasional heavy load of fuel for the ion engines.
But these carbon cables are nothing to sneeze at. there are going to be a lot of uses for then in space and more down to earth construction and engineering jobs.
ahem.
http://www-istp.g...her.html
great idea. i hope they try it. but i doubt it will be feasible, at least not in one great long wire from heaven to earth.
As for induced current, the study paper I posted the link to has this to say, although they are talking primarily about electromagnetic heating.
"Heating of the cable can be produced by passage through the local magnetic fields. The
potential induced along the cable can be expressed as:
E = B(r)v(r)
where E is in volts/meter, B(r) is the magnetic field, and v(r) is the velocity of the cable relative
to the magnetic field. For radii (r)
Continued:
for radii less than 10rEarth, B(r) ~ 0.35_10-4rEarth
3/r3 and v(r) is approximately
zero. However, if we assume the worst possible case where the magnetic field is fixed and the
cable is rotating with the Earth (v(r) = 463 r/rEarth m/s) we get potentials from 0.00026 V/m at
10rEarth to 0.016 V/m at Earth%u2019s surface. At distances of greater than 10rE, the cable is in the
interplanetary magnetic field during the day (Bave ~6 nT and Bmax ~80 nT) and is in the Earth%u2019s
magnetosphere at night. This corresponds to a maximum potential of 0.00068 V/m at the far end
of the cable. With a minimum resistance of 0.4 W/m we have a maximum of 0.0064 W/m of
heating occurring near the Earth end of the cable and 1 mW at the far end. The cable would
quickly radiate this level of heating away into space.
any offensive weapon is also a defensive weapon, just as any defensive weapon is ultimately an offensive weapon. it just depends on who is attacking, and who is being attacked, to make the determination of whether a weapon is being used as defensive or offensive. Weapons are just weapons...not sure how weapons and terrorists got brought into this though. The terrorists aren't that good anyways...its just a bunch of religious idiots who think everyone in the world but them wants to kill their religion off.
KBK-damn good post
daqman-you also have the cable to help support the elevator platform, so since its not suspended in thin air, i wouldnt think the nergy required to exit earths gravitational pull would be anywhere near that required for a rocket. that of course entails the idea of some friction/clamping effect on the cable itself (which if they put brakes on, shouldnt even be a question of whether that will exist...i know id want brakes on that beast if i were screaming back at the earth from 20000 miles up on an elevator (literally in this scenario) :D
nklanaga-good references; good math :D oh and good later addition too :)
joey tavarez- you forgot, its auto pilot with the bush administration at the remote control end :D
seanpu-i do agree, but the material in teh nanotubes, as mentioned as these guys who layed out the specs on teh strength of those things, VASTLY outdoes the material mentioned for the last attempted tether...that could make the difference there. i do agree though, this probably isnt feasible...
phlipper-ahhh, but you would/could put multiple smaller windmills creatively around your car (for instance, inside the grill, in the wheel wells, in front the the lower air dam if youve got a sports car, etc., that would cause no more drag effect than those items do themselves (especially if you catch it immediately at that break point anyways). so that is actually feasible, and an idea ive been tooling around in my brain for a couple years..although i just gave it away so now well see it on the market soon :)
here again you are suggesting that energy can be collected without a complete circuit. to generate power in this way there would have to be a return sytem for the electrons to return to the atmosphere. All, I repeat ALL electrical circuits form a complete loop.
I think you need to read up on your tesla.
I can back this with a lifetime of work.
Returning to your comments re Tesla, what I imagine you are talking about are his transmission of electricity through the air. what you do not realise is that for ny device to use this type of transmission it had to be earthed (connected to the ground) this is what provides the return the ground itself. Non of Tesla's experiments are unexplainable and all include a complete loop circuit in some form or other but this may not be imeadiately obvious.
let me offer you further evidence: some time ago an attempt to generate electricity was done by towing a single cable behind an orbitibg craft so that the cable passed through the earths magnetic field. It did not work and the cable blew itself apart. It would have worked had they formed the cable into a loop and dragged this through the earth magnetic field. what happened was that the single cable generated so much static it blew apart in a form of lighning. If you would like to offer any example of flow without return for electricity I will be glad to explain how it is really working.
regards
Tony
all of those ideas are on the horizon.i would personally look to things like suspension bridges being the first to incorporate these items in an industrial production model.