h a l f b a k e r yRIFHMAO
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Now that they're making twine out of carbon nanotubes let's hurry up and build an elevator to space. We'll attach it to an orbiting satelite. With nanotubes there shouldn't be a problem with tensile strength. I know, I'm not the first to suggest using a tether as a form of space transport; my idea
is for us to hurry up and do it. I'd like to see some major space exploration done in my lifetime.
Nanotube fiber for sale $1000/g
http://news.bbc.co....1030000/1030420.stm
It shouldn't be too long before we've got nice cables... [flapmaster, Dec 15 2000, last modified Oct 21 2004]
Ribbon to the Stars: Pushing the space elevator closer to reality
http://www.sciencen...g/20021005/bob9.asp
Added 16 Oct 2002 | A recent article on the possibilities of building an elevator to space.
Includes the history of the concept, which dates back more than a hundred years. [bristolz, Oct 16 2002, last modified Oct 21 2004]
many slashdot articles on this subject
http://slashdot.org...160§ion=&sort=2
[utexaspunk]
Not So Half Baked
http://www.space.co...levator_001226.html
Space Elevator: Next stop, Earth orbit! [utexaspunk, Oct 04 2004, last modified Oct 21 2004]
Not So Half Baked
http://www.space.co...levator_001226.html
Space Elevator: Next stop, Earth orbit! [elevator, Oct 04 2004]
The space elevator!
http://www.highliftsystems.com
Web site devoted to the idea of a space elevator [elevator, Oct 04 2004]
Even NASA are thinking about the idea!
http://science.nasa...2000/ast07sep_1.htm
During a speech he once gave, someone in the audience asked Arthur C. Clarke when the space elevator would become a reality. Clarke answered, "Probably about 50 years after everybody quits laughing." [elevator, Oct 04 2004, last modified Oct 21 2004]
Space Elevator Update
http://story.news.y...highhopesloftygoals
I found this interesting [SystemAdmin]
Online nanotube sales
http://www.cnanotec...0_online_store.html
Start building your own! Be the envy of your friends as you ride your personal elevator to space. Some assembly required. [SystemAdmin, Oct 04 2004, last modified Oct 21 2004]
Online nanotube sales
http://www.cnanotec...0_online_store.html
Start building your own! Be the envy of your friends as you ride your personal elevator to space. Some assembly required. [Worldgineer, Oct 04 2004]
NYT Science Desk -- "Not Science Fiction: An Elevator to Space"
http://www.nytimes....anted=all&position=
Added 23 Sep 03 | A story about Los Alamos Labs recent 3-day conference on the subject. The conference kicked off with a keynote speech by Arthur C. Clarke. [sorry, NYT free subscription req'd to access] [bristolz, Oct 04 2004]
Space elevator competition
http://www.telegrap...09/25/ixportal.html
No, I can't believe it either. [wagster, Oct 03 2005]
Desert Space-Scraping Arcologies
Desert_20Space-Scraping_20Arcologies
See [david_scothern]'s figures about half way down giving the maximum height of a man-made structure. [wagster, Oct 04 2005]
Tether climber test wins NASA prize
http://www.newscien...000-nasa-prize.html
A paltry €900,000 [wagster, Nov 09 2009]
A space elevator -- for the Moon!
http://www.forbes.c...vator-for-the-moon/
[theircompetitor, Aug 28 2012]
[link]
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Barring incident, 80-100+ years is probably not too long a time to expect construction to take, so you're right: they better get started soon if you want this in your lifetime. |
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The Tower of Babel was mankinds most [in]famous attempt to reach into the heavens. |
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it need not rely purely upon the strength of the nano tube. |
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as a completely impractical measure it could be helped by a huge air-pressure and mag-lev based tube that would surround the lift car and help to provide lift |
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Nice link bristolz. I have *always* believed in some form of this and to think of all that resistance for the "Organic Space Elevator"... |
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way half-baked. it gets talked about on Slashdot at regular intervals, and Arthur C. Clarke wrote about it. |
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I read somewhere (was it the Guiness Book of World Records?) that folks can't take elevating at more than 22 mph. This means that if the terminal was 2200 miles, it would take 100 hours to get there. |
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Is there any truth to this? |
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No. All you can feel is acceleration, not speed. 1 "G" is 32.2 feet per second per second (9.8 m/s^2). This means that if you're accelerating enough to feel twice as heavy (2 G's), you'll be going an extra 32.2 feet per second faster every second - this can get you moving quite fast fairly quickly. Actually, 32.2 ft/s^2 is about 22 miles per hour every second. In a minute you'd be going about 1,320 miles per hour. |
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Some days I feel like my neck is an elevator to space. |
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The idea of a space elevator is widely discussed in the books Science of the Discworld, and Science of the Discworld II, by Ian Stewart, Jack Cohen and Terry Pratchett. They make quite a good read too. |
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Hang on [Worldgineer] is this elevator going to speed up and slow down every five minutes? I figured more than on customer would be riding this little baby at a time. Isn't it supposed to be a balanced load going up and down continuously. I guess perhaps we could load the first ten carriages then swishhhh off it goes at 1320 mph. I dunno I think this needs some more thought. |
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world engineer, i dispute your maths 1,320mph = 2124kph |
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t= 2124334/(9.819x2)= 108273 s = 1804 mins = 30 hours |
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correct me if i am wrong but this is some what longer than your claimed time to reach 1320 mph |
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you would need to pul 3613g's to reach 1320mph in a minute |
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[Tiger Lily] What a strange and intriguing thing to say. Care to elaborate? |
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Engineer1, I think you swapped a denominator somewhere. |
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1320 mph *5280 ft/mi = 6969600 ft/hr
6969600 ft/hr / 3600 seconds/hr = 1936 ft/second
1936 ft/second / 32.2 ft/second^2 = 60.1 seconds |
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Accelerating at 1G (2G perceived due to gravity) will result in 1317.2 mph after 1 minute. |
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I think [e]'s (first) mistake was in the conversion. 1320 mph converts to 590.0928 meters/s, not 2124334. Ok, enough picking on [e]'s math (I've certainly made my share of silly errors). |
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[Pain], I don't think it has to be a balanced load (unless you mean balanced around the nanotube). |
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[Tabs], I assume you can continue to accelerate as the air gets thinner (well, until it's time to slow down). |
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The problem with all these elevator ideas: the coriolis effect. Any object sent up the elevator would pull the satellite West-wards. A lot. |
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Seems to me you could control that by reeling in and out the line. Keeping the station further out means more outward force, which should counteract any westward-tending force. |
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[worldgineer] That's where my balance comes in. I thought that the net amount pulled up the tube line would equal that coming back down the tube from space. (read: moon junk or tonnes of valuable minerals). Hence the balance is kept even (albiet at the cost of not being able to have 3560g acceleration) Do you get what I mean now? like a grain elevator but with little men coming down the other side. Got to catch a 1320mph elevator that doesn't stop but keeps going like a seeyah wooahahhhh!!! (cheers tabs) |
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Yes, but I don't see how the reeling in and out wouldn't fix that issue. |
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I don't really see how reeling in and out would help with the coriolis force. Balancing the force by sending stuff up and down at the same time also does little, unless it's a constant flow. A single mass starting up from the bottom and a similar mass starting down from the top will balance out any potential changes in center of mass, but since the mass moving up will tend to pull the cable west and the mass moving down will tend to pull the cable east, there is still going to be a rather nasty force imbalance on the cable. |
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So the satellite is positioned way out to provide the pulling force. The object starts rising, and needs to be accelerated East-wards. It is accelerated by the cable. Assuming the satellite pulls the cable hard, the result is like a guitar string. The object will pull the cable like a finger plucking the string. The forces in the cable will increase tremendously. |
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Since this started with carbon
nanotubes, has anyone checked things
like tensile strength and all that? Not
saying I have, but I'm pretty sure that
carbon nanotubes aren't such a big
help. In terms of tensile strength,
they're not great (eg, piano
wire=450,000 psi, carbon n.t.'s
300,000 psi), though their density is
lower which helps. The only thing that
carbon fibres excel at compared to
older materials is in specific Young's
modulus (stiffness per unit mass), as far
as I can find out. And is stiffness the
main problem for the space elevator
which is presumably in tension? Most
of the engineering applications of
carbon fibres that I can find are in shell/
sheet structures (car and 'plane skins,
stuff like that), where *stiffness* per
unit weight is the main requirement,
not tensile strength. They're not used
in pure tension structures, not least
because the work of fracture is lousy
(ie, cracks spread). So, not sure they
help a lot..... |
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Links I've seen indicate closer to 600,000 psi for tensile strength. |
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Didn't Led Zepplin write a song about this sort of thing? |
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There's a engy who's sure |
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That his 'tubules will hold, |
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So he's building.... well, you get the picture. |
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Carbon nanotubes have a tensile strength of 63GPa (wikipedia) However I've heard that nanotube 'twine' isn't so hot on the tensile strength front. |
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It'd be nice if we could produce 36000 km nanotubes, as far as I'm aware they're sometimes produced from a cloud of ions 'assembling' at the free end of the tube, I wonder if anyones tried reeling them as they're produced, guess I'll have a little look on google. |
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One problem I can see is what happens to the tube in lower orbits? Do all other satelites get routed around it? That's a lot of satelites! |
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The strength of any twine is partially dependent on the length of the fibers in use. A short fiber will not have enough inter-fiber friction to prevent the piece of twine from simply pulling apart, even though no individual fibers actually break. As the length of the fibers increase, the inter-fiber friction increases, and the individual fiber strength becomes the deciding factor in how strong the twine is. |
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High-friction materials such as sisal and hemp don't need particularly long fibers, although it helps. Any fiber endpoint can be considered a small break in the twine, and is structurally useless at that point in the twine. Therefore, longer fibers produce a higher strength-to-weight ratio for the same material. |
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Low-friction materials such as carbon do not naturally produce a strong twine, as extremely long fibers are needed to yield significant inter-fiber friction. In these cases, a structural binding agent with a high shear strength is used to prevent the twine from simply pulling apart. Again, long fibers are still useful, since a long fiber will have more surface area for the binding agent to act on, reducing overall intertwine shear forces. |
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In constructing a space elevator, the tensile strength alone is not as important as the ratio of tensile strength to weight. Even if steel is stronger, it is much heavier, and the major structural load in a space elevator is caused by the weight of the structure itself. |
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//In constructing a space elevator, the tensile strength alone is not as important as the ratio of tensile strength to weight. Even if steel is stronger, it is much heavier, and the major structural load in a space elevator is caused by the weight of the structure itself.// |
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A fine point, it's probably better just to have a nanotube cable pulling a continuous series of pay loads into orbit using the tension provided through centrifugal ation. No need for any structure therefore cheaper, less structure for satellites to hit or wind to add extra loading to. |
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<edit> sorry just realised that the centrifugal tension idea doesn't add up if the satellite is further out than geostationary orbit it's just no longer geostationary, and maintaining the centre of gravity at geostationary orbit while attaching and detaching payloads might be a problem</edit> |
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"my idea is for us to hurry up and do it"
Wow... This idea got 6 buns!
Coming soon... Hover Cars... I know its pretty common in alot of Sci-Fi shows, but my idea is to hurry up and do it!
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[MO] hologram televisions are baked already, good point though |
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<edit> as have Hover Cars </edit> |
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I am laughing cos i am at work, and anything seems amusing in comparison!
I am amazed that the idea "hurry up and do x" has endured 3.5 years and has 6 positive votes (and only 3 negative when i first annotated).
An interesting insight to the bakery's early years!
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Just think of the scandal if someone posted this today! |
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edit. I changed from hologram teles, cos i thought of a better example! |
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[mo] was tempted to [m-f-d] this for the reason you gave, but looking back it seems to have generated a lot of interesting anno's |
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Has anyone figured in the torque created by the earth's rotation? Wheeee! What a ride!
Maybe I missed it in all this diatribe. |
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The race is on! The X prize is to be repeated with space elevators - first one up there wins. You think I'm joking don't you? Check the (link). |
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That's odd - Clarke had an article in The Times about this just last weekend - I thought it was just a plug for Fountains of Paradise, which is to be made into a movie (according to ACC).
36000 km even at Mach 1 is going to take 30 hours - a day and a quarter listening to Muzak, and trying to get to the other side of the car from the unpleasant smell. |
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Plus, what if you're going from here to the moon, and after you get in you realize someone has pressed all the buttons? |
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That's OK if there are only two floors. I suppose other floors could be the ionospheric floor, geo-sychronous floor, ISS floor, viewing gallery, suicide floor etc. |
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Anyway, I think someone already proposed a cancel function on the HB. |
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Didn't [david_scothern] do some proof that structures over fourteen km high were impossible (link)? Even if they are being pulled up from above as well, wouldn't this be an issue? |
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Per [MauiChuck]'s earlier question, //Has anyone figured in the torque created by the earth's rotation?//, the coriolis force would be approximately 7*10e-5 * vertical velocity * mass of the elevator "car".
This works out to just under 0.05g horizontal acceleration at 695 meters per second (1 g acceleration for ~70 seconds, same to decelerate), which would get you to geostationary orbit in about 12 hours. If you go faster, the load is higher. If you go slower, the load is lower. The tension that this would put on the cable is dependant on how much the cable is allowed to deviate from vertical, i.e. "how far can it be pulled?". |
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This means that small loads could go up fairly quickly, but large loads would take several days or weeks. But, since you're not carrying your fuel along with you, it would still be fairly cheap. |
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I believe the original idea is to start putting up tethers right now, but from what everyone is saying, we need more research to find out if it's possible, let alone to get it done. |
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They've just built a climber (link). |
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The major consideration in a structure of this length is taper, which is a function of strength to weight. In order to support it's own weight a steel structure to low earth orbit has to have a larger base than the diameter of the planet, which is not real practical. A structure made of long continuous nanotubes has a taper of factor in the range of 20-40, that is a cable 1ft in diameter at the bottom (assuming anchored in geosynchronus orbit) will be about 40 ft in diameter at the top. |
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To respond to basepair's anno (from 5 years ago), carbon fiber composites are prone to cracking because the fibers and the matrix separate easily. While this is still a major problem with nanotube composites, it is not a problem with twine or continous tubes. |
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Admittedly the minor problems still exist that the maximum fiber length so far is in the cm range (seriously, like 4cm or so) and that getting the fibers to stick is a problem which means nanotube cloth or twine is nowhere near as strong as individual fibers. |
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I assume that if you were to make a rope by binding together these really long nanotubes that don't exist yet, there'd be almost no friction on the surface that a climber could hand on to? |
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//no friction on the surface that a climber could
hand on to?// That's why there'd be a ladder
propped up against it. |
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Hence the iconic E.T. opening phrase: "Take me to your
ladder." |
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Nanotubes aren't the best surface for a climber, but
it shouldn't be a problem to get a climber to work.
Remember that even if they have a relatively low
coefficient of friction they can stand up to a heavy
clamping force to provide a high total friction force. |
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