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Notes From 3rd Annual Space Elevator Conference
colonist writes "The Space Elevator: 3rd Annual International Conference was held recently. Blaise Gassend, a PhD student at MIT, took notes. The main obstacle is still the material: transferring the strength of the nanotube to the ribbon. Other topics include: the nanotube tether Centennial Challenge; Elevator 2010, a challenge for a 250 kg climber to climb a 16 km tether; objections and refinements to Bradley Edwards' design; non-equatorial space elevators; replacing the term 'space elevator' with 'space bridge'; testing the space elevator material on cable cars; science; defense and economics."
This page seems to have some good links. Just check out the bottom of the page as it indicates if you're new to the idea of space elevators.
Wikipedia have a very good article on space elevators
Normal GPS satellites are not in geosynchronous orbit.
Some augmentation satelites are though.
Jeroen
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I believe the point is to make access to space economically practical. Burning massive amount of fuel is pricey and pretty bad for the environment. If we really want to be doing stuff in space we either use space elevators or wait for someone to invent anti-matter drives or something.
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We spoke for about a half an hour. I don't recall a thing we said. - Colorblind James Experience
Not in the fairytail....
But there is archeological evidence for a lot of towers in what is now Iraq and Iran.
Among them some very big ones in babylon.
Jeroen
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Well, actually, a little further out than GEO, so that the center of mass is at GEO.
As for wind -- well, you situate it where the wind is minimal. Remember, since it's synched, it's not generating "wind" by slicing through the air. All you'd have to worry about is the wind that is actually blowing past the (stationary) Earth.
The Mongrel Dogs Who Teach
That's why you need a really strong material for a space elevator - if it wasn't for the weight of the "rope" itself you'd only have needed a material strong enough to handle the weight of whatever you wanted to transport up it, but that is a miniscule amount of the total strain on the elevator.
Ignoring the weight of the rope itself, probably the main reason for this rule-of-thumb is the difference between dynamic loading and static loading.
If you (accidentally) get something bouncing on a short rope, the bounce will damp out pretty quicky and the period of oscillation is short. If you get something bouncing on a long rope, it will bounce for a while, and the rope is stretched for much longer with each bounce. It doesn't take all that much of a bounce to double the load on a rope, and perhaps take it past its elastic limit.
I'm guessing, but I think that pre-synthetic ropes probably can be briefly overstretched without losing strength because they knit back together again. If you continuously overstretch them, the fibres probably don't get a chance to recover before the slide past each other a little more, and so on.
So my guess is this doesn't apply nearly so much to modern synthetic ropes. In the case of a space elevator, I'd hope they'd try really hard to avoid excess dynamic loading.
Your example of a chain is flawed and doesn't match what you suggested for the rope - A chains strength doesn't weaken for each extra link because of "small flaws", it stays the strength of the weakest link regardless of number of links.
But the moment you start hanging it down you need to take into account the weight of the chain itself, and the chain, just as a rope, will be able to lift less additional weight the longer it is because the strain on any point of the chain/rope is equal to the weight attached PLUS the weight of all of the chain/rope below it.
The text of Tank Farm Dynamo is online.
I wouldn't worry about being killed by a carbon fiber making meteoric reentry. It wouldn't be like the disaster in the Mars trilogy, or even like shadow square wire... by the time it hits it'll be more like laser toner, the stuff is strong in tension but it burns quite nicely: Nanotube Explosions
While Arthur C. Clarke certainly popularized the idea of a space elevator in his science fiction novel "The Fountains of Paradise", the original concept is credited to the Russian engineer Yuri Artsutanov, who published it in 1960. See, for example, here
Ubi dubium ibi libertas: Where there is doubt, there is freedom.
It's easier than most people think, you don't need to capture an asteroid. You send up a small counterweight along with the initial spool of cable, and as the first cable unspools downward from geosync, the counterweight moves up. You end up with the first strand of cable fully extended with a small counterweight, just enough to hold itself and a small payload. From there it's trivial, to add more cable you carry it up the initial cable, and to add more counterweight you have the cable-laying climbers go all the way to the end and become part of the counterweight, and/or send separate climbers to carry up the counterweight.
Nothing.
It's a ribbon. It's literally nearly equal to the weight of an equal width of Saran Wrap.
How much unrolled saran wrap do you have to drop on someone before it hurts them?
How many buildings will be devastated by having something that flimsy dropped on them?
The devastating space elevator fall is bad science fiction. If it breaks, stuff above will stay in orbit, and stuff below the break will fall harmlessly.