I have been giving a lot of thought to space elevators recently, and wanted to run a few trhings by the collected wisdom that is Vortex.
I have seen a lot of talk about how easily the cable could be damaged, but I'm wandering if they didn't forget something. Current estimations using carbon nanotubes predict a cable no more than a couple square centimeters in cross-section (average), and some are predicting less. With the tension on the cable, what prevents it from mimicing a cheese-cutter, and slicing right through anything unfortunate enough to impact it? Granted, that doesn't apply to the liftport group's concept, they have their cable flattened into a meter-wide ribbon, and presumably the strands in the impact area would not be up to withstanding an impact. Which brings up my next point, possibilities of damage from terrorism are estimated to be high, simply from the stature of the elevator, but honestly, how hard would it be to fly an airplane into a target that is at most 1 meter wide? ------------------------------------- Enough with generalities, the cable/ribbon design I favor would actually be four cables, interconnected. Each cable would be slightly dumbel shaped 0-0 (although without the sharp corners), and approximately 3 cm wide and 1/2 cm thick. A pair of these cables would be interconnected 0-0><0-0 for a total width of 10 cm. This would then be similarly connected to the other pair 0-0><0-0>-----------<0-0><0-0 for an overall width of 1 meter. The interconnections between the cables would be an open lattice of small fibers at 45 degree angles to distribute forces in the event of a failure. Elevator cars would travel up one pair of cables, and down the other pair. The dumbell shape allows the car to get lateral grip, allowing it to hang off the side of the cable. Each cable would have a safety factor of 1.5, meaning it can carry 150% of the expected load. If a cable breaks, then the extra load is distributed to the other three. Due to the interconnected nature of the cables, at least 2 cables would have to be broken within a fairly short vertical distance to cause failure. There is a formula (which I am too lazy to track down and retype) which can be used to determine the minimum cable cross section at an height for any material, and IIRC the result is that a CNT cable would have approx. 9x the cross section at GSO as at the surface. Granted, by dictating a that the cables can carry 50% more load that would increase, but probably not more than 2x-4x. <shrug> just something to while away idle neuron time. Merlyn Magickal Engineer and Technical Metaphysicist __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
