The world's best science fiction writer, also known as Arthur C Clarke, invented the communications satellite that makes most things go 'round. Since then, he's come up with more brilliant ideas, some of which may become reality in our lifetimes. The space elevator uses a geostationary satellite physically linked to Earth with a cable. Instead of blasting tiny payloads into orbit atop long skinny bombs, we could lift big stuff with very little power. Not just any cable will do, which is part of why we haven't seen one yet, but one made with Buckminsterfullerene, also known as carbon nanotubes, may just do the trick. Recently, my favourite writer was asked when we might really see a space elevator, and he replied "About 15 years after everybody stops laughing." Are you laughing too, or could this really work?
There are a bunch of people working on it here in the Silicon Valley. There was a recent NASA Ames Research Challenge Project working on some of the problems. As you noted - the current thinking is Bucky Fibers may be strong enough to handle the strains. But no one has made a long enough Bucky Fiber to find out yet. It will happen in the next 20-25 years. Lisa PS Come back in 20 years and it will still be 20 years out... :wacko:
Ah yes, Bucky Fuller... ..anyone ever hear of "Tensional" "Integrity" "Tensegrity", and how it relates to... ...Carlos Castaneda h34r: To answer the question though, I sure as heck believe it. Anything IS possible.
Laughing. After I'm dead....if they finally get it working it won't matter if I'm embarassed by my short-sightedness. As much as I admire Clark...I'm shaking my head on this one. I will say it's high time we had three permanent space stations in orbit around the earth. Big ones. Really big ones. With expansion capability. Then....start working on a permanent facility on the moon. International....like Antarctica.
Nope. Won't work. The reason is that simply the act of pulling on the cable (to raise a payload) will perturb the orbit of the satellite enough to throw it out of geostationary orbit. Once it moves away from the precise point of G/S orbit it will begin to wind itself in, thereby moving farther off its point, and wind itself in even faster. To prevent this it will need enormous amounts of fuel to maintain the proper orbit, and you're back to the same problem as now. Also, the weight of the cable itself will be an issue, and since that weight is distributed over its length, each centimeter of the cable will have its own natural orbital velocity so there will be huge sideways strains on the cable. Even imaginary as-yet-uninvented fibers like buckminsterfullerene will have significant weight when the cable must be as long as that. Another issue is collision of space junk with the cable. If the cable breaks, the bottom half will come flailing back to Earth and the satellite, freed of a downward pull, will move outwards away from G/S orbit, and if it holds, the force of the collision will again pull the satellite out of G/S orbit. There is so much space junk right now that launch windows have to be precisely calculated to avoid collisions. It would be necessary to assure that no satellite or piece of one ever crossed the path of the cable.
it will work. being in the Earth gravitational field influences our perception of mass verses weight. its mass that force relies on. not weight. what would seem like more than enough to pull the station down could easily be counterbalanced in space. the entire concept of this idea hinges on that concept. the space station weighing thousands of ... millions of... well weighing a lot, but in a weightless environment would need much less energy to say "widen its orbit" temporarily in anticipation of the tug of a load coming up its tether. the difference in the amount of energy to bring an object up in this fashion verses what we do now is huge. if it can be done, it would be one of the greatest energy savers known to man.
It can work, but it can't be sats in geo-sync orbit. Daniel right, the pull on the cable in that setup would eventually disturb the satellite from its orbit. The only way I can see to make it work is a full circle satellite built al the way around the earth (and yes, that is a monsterously enormous project.) A few cables going up like spokes would balance the forces used. If you pull on one cable, it would try to pull the structure down. Because it is a circle, though, one side down means the opposite side goes up. The opposing cable provides the resistive force, preventing the motion. Can we do this? Probably, but not any time soon. By the way, there absolutly IS gravity in orbit and it must be taken into account. Without gravity, there could be no satellites. An object in motion will continue in a strait line unless acted on by an outside force. Gravity is the ONLY force that can can provide the angular acceleration to curl a satellites path around the planet. You can experiance relative weightlessness in orbit though, as gravity acts on the ship and you in the exact same way, with nothing to draw or repell you from the ship.
Well, even in space there is no such thing as "zero" gravity, there is still microgravity. As a teenager I read "Fountains of Paradise" by Clarke and found it imaginative but somewhat lacking in details. It should be noted that Clarke took awhile to come up with precise geostationary orbits for what we now call the Clarke Belt. When I was first in college I read, and liked so much I purchased, "The Endless Frontier." It was edited by Jerry Pournelle I beleive. One of the short stories had very detailed ideas about "skyhooks" and the brief did mention the orbit would perturb. The "skyhook" would also require a counterbalance out into space to keep proper tension on the earth station. I should look through my library and see if I have it at my condo. I hope it's not at the hobby farm, I wasn't planning on going out this weekend. Too cold.
Agreed, Heinlein. BUT, I admire and appreciate Clark, after all, I sell satellite systems. As for the elevator...nope, not practical in any sense, and the freedom of individual space travel by individual vehicles will be available before any such construction could be produced. As an example, I think travel by train is great, but if travel by car is just as easy, the car wins. And, I wouldn't want to take a train UP. However, as Clark said, "any technology sufficiantly advanced will be indistinguishable from magic" or something like that. So maybe I can't see it yet. Rod
It sure sounded good on Science Friday with Ira Flatow. He interviewed a guy whose company is trying to develop nano carbon fibre ribbon (Bucky Ball stuff I guess?) He wanted to put the base station out in the ocean on the equator. Not being the sharpest tool in the PriusChat shed it's way over my head but sounded very exciting.
nitpickers... ok fine... there is no zero gravity within reach of Earth. however, the energy savings is still immense. this would allow us to expand the station indefinitely (ok better strike that word!) . now creating one that completely circles the Earth is out of bounds. even in GREATLY REDUCED gravity, it would be way too massive to hold together. and the pull from the tether problem is so easy to solve its not even funny. we have had issues with satellites that are unmanned therefore difficult to repair that fall out of the sky. with the tether, we simply program it to counteract the pull of the tethere by nablnig a slightly faster than normal speed which will under normal circumstances cause the station to fly away. but instead will only keep just enough tension on the line. (not to mention that we could get a tech crosstrained in rope climbing to pop on up there to fix the thing.) now no more skylab incidents. (remember that was the station that lost its orbit and crashed to Earth.)
I'm holding out for transporters. Either the human designed kind, ala Star Trek, or just given by the Azgard, ala Stargate.... I'm not picky. The elevator cables are too messy.
I found that book "The Endless Frontier" and it was actually a Russian design. "Kosmos na Elektrovoze" or something like that, the author Artsutanov. Then-current construction materials were totally impractical, but materials with much higher strengths made it practical. As an example: a synchronous cable made of steel would have to be 10 to the 50th bigger - the taper - in the middle than at the end, and weigh 10 to the 52nd what it could support. Impractical. A Kevlar cable would need a taper of 10 to the 10th, and would have to weigh 10 to the 13th what it would carry. Also impractical. A single crystal graphite whisker would have a taper of 10, and would weigh 400 times what it had to carry
I respectfully disagree. There have been some big minds at work on this for some time, and the issues you cite are not supposed to be insurmountable. There is an article in the current Air & Space magazine about space elevators. Pretty interesting, but I do doubt that it will become practical.
. . . then . . . there’ll be spandex jackets, one for everyone. :lol: No doubt, space elevator sure would bring a new level of excitement to the world of BASE jumping. One potential problem I heard about, and it's not mentioned in this Wikipedia article, is the possibility of short circuiting the earth's electromagnetic field. http://en.wikipedia.org/wiki/Space_elevator.
Whatever happened to using commercially produced spider silk for this application? Anyone remember the genetically engineered goats from a few years ago? The goats' milk contained the spider silk proteins which could then be drawn out through a mechanical spinner. I always picture goats swinging from the ceiling, though.
A Mexican children's song goes: Un elefante se columpiaba en la tela de un araña, Como veÃa que resistÃa, fue a llamar a otro elefante. Dos elefantes se columpiaban en la tela de un araña... Very roughly translated: One elephant swung on a spiderweb. Since he saw that it held, he went and called another elephant. Two elephants swung on a spiderweb... And it goes on forever, adding one elephant at a time. The song has no end. But to the topic of this thread (no pun intended) nobody has addressed the issue of space junk. And as strong as that single-crystal carbon thread may be along its length, a bit of space junk could sever it pretty easily. And I still say that moving the satellite in or out to counter-balance the changing stresses on the cable, would put it out of G/S orbit and cause it to move away from its anchor point, and in effect, wind itself in. Picture the earth as a yo-yo and the satellite as your finger. Plus, although the energy needed to raise a payload is less than using a rocket, that energy must be ON the satellite, which means lifting the fuel. If it takes a pound and a half of fuel to raise a pound of fuel to the satellite, you've got a net-loss equation and the system fails. I say it's impractical, if not impossible. And if you suggest having a pulley on the satellite, and pulling from the ground, I point out Jayman's citation of the variable thickness required of the cable, requiring that it be static.
As far as collision with space junk, I think that would be a *great* tourist attraction. Everybody is familiar with how a car looks after a high speed crash, now imagine a collision at many thousands of miles per hour. BASE jumping from the Troposphere, that would also sell. Of course, you'd have to get legal waivers from the jumpers, so when they re-enter like a meteorite and vaporize, the family can't sue. I think it would be cool to short out the earth's electomagnetic field. Aren't we long overdue for that field polarity shift anyway? Interesting idea, but perhaps several hundred years from now when they get all the bugs worked out. In the meantime, I'd happily pay for a genetically-engineered goat that could swing from my ceiling. Just to keep my cat in line.
