Slashdot Mirror
Highlift Systems' Space Elevator In The News Again
Kris_J writes "Highlift Systems may have found a second location for the anchor of their space elevator -- Perth, Western Australia. Apparently we have the calm waters and international airport that it needs, amongst other things. Slashdot has covered this company's efforts before: Oct 9, 2002 and, earlier, August 13, 2002, but it's worth discussing again since '[recent funding] has been given momentum by the Columbia shuttle disaster.'"
http://www.howstuffworks.com/space-elevator.htm
Centrifugal force. I have the .pdf file, the examination on the plausability of this working. The cable would be 60,000 miles long. At this length the force of the Earth spinning would hold the end of the cable outwards in a straight line.
The first cable would be 1 micron thick, and taper from 5cm wide at Earth to 11.5cm in space. This would be added to each climb. By the 107th addition it would be capable of holding a climber of 22tons with a 14 ton payload.
Of course it would be made of Carbon nanotubes (the only thing that could possibly be strong enough and light enough).
Now I'm not saying I believe it can or will be done. I'm only quoting Bradley C. Edward's paper.
It's not a stupid question. Get a ball on a string and whirl it round. The ball doesn't lag does it? The outward pull of the ball keeps the string taut. The exact same effect will be used by the elevator. Locally, in the atmosphere, the cable will be stationary, so it will have to resist wind loads, but they have worked those out. There is also some drag due to space debris and solar wind, but again they have accounted or that.
Good article, nice website, fantastic project. As Arthur C Clarke said (I think, loosely), we'll be using a space elevator about twenty years after everyone stops laughing at the idea.
First of all, theres no way that the structure could be supported solely from the ground, the bottom is anchored, but thats not why its rotates with the earth. Rather, the top is anchored to some heavy object (read asteroid or the like) that is (somehow) placed into a geosync orbit. The structure merely provides a way to efficiently travel from earth to the other object (as you have a solid medium to push against and facilitate the change in grav. potential).
P.S. Yes, technically the orbit of the top of the elevator/upper anchor is not geosync, but rather slightly above geosync to allow for the center of mass of the contraption to be geosync in its orbit, (and the bottom anchor then serves to maintain the proper orientation).
**AA: a bunch of mindless jerks who'll be the first against the wall when the revolution comes
There is NO SUCH THING as "centrifugal force". "Centrifugal force" is the effect of tension in a cable against the center of rotation caused by CENTRIPETAL force accelerating the swung object towards the center.
It's like this...a car pulls a trailer. The car is pulling the trailer! There is a force acting backwards on the trailer hitch on the car, but it is actually the car pulling the trailer, not the other way around. The anchor is not pulled by the swung object, the anchor PULLS the swung object.
If the string is cut, the object does not accelerate away from the anchor because of some centrifugal force; the object will STOP accelerating and continue along in a straight tangential line.
Centripetal force is real, centrifugal force is apparent.
The above post makes an excellent point, there is currently no material that can sustain the enormous stress that would be required to construct a space elevator.
While there is no current material that yields the necessary strength/mass required in order to built a space elevator, realistic possibilities are on the horizon. Quite simply, with the advent of nanotechnology, we are nearing the technological feasibility of creating a material composed of intertwined nanotubes. This is theoretically the strongest material that can ever be created. Carbon-Carbon bonds are extremely strong and would be extremely densely packed in a nanotube pole. It would be an order of magnitude stronger than steel, as well as significantly lighter.
While nanotubes can already be readily produced (Dr. Smalley of buckyball fame operates a production facility), strong nanotubes rods have yet to be produced. This is due to a variety of technical hurdles that must still be overcome. Perhaps the foremost obstacle is getting the produced nanotubes to lie parallel to each other. The current production method has the nanotubes forming from a catalyst and then becoming intertwined in a jumbled mess. When tension is applies to the mesh, the rope breaks not within the nanotubes (which would require a great deal of energy), but between the nanotubes, unraveling them from each other. Attempts to get the nanotubes to align properly have failed. Nanotubes are not an easy molecule to work with. They have extremely strong cohesion forces and are very difficult to pull apart from one another. The obvious approach of functionalizing each nanotube in order to orient it correctly doesn't work as doing so causes the nanotube to lose much of its mechanical and electrical promising properties.
In addition, when nanotubes are put under extreme mechanical stress, the bonds within the nanotube shift. For example, I've seen simulations where the bonds separating two polygons disappears, creating what appears to be a bonding who in the nanotube. The hole then resonates through the nanotube causing significant weakening in the structure.
At a talk I attended, the most promising idea I heard discussed was a steel/nanotube alloy. The nanotubes would run vertically through the steel, reinforcing the structure in the same way steel rods are often used to reinforce concrete. This would alleviate the risk of the nanotubes becoming unraveled intermolecular while at the same time using their large intermolecular strength to reinforce the structure.
Of course, without any physical models, this is mere speculation. However, it suffices to say that a there are real possibilities of breakthroughs that would allow for the construction of such a space elevator.