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The Engineer in Me.
As one Engineer to another, this isn't an elevator cab which is either a cable suspended or a hydraulic lifted cab. The plan for a space elevator has always been to have several cables, with an electric current in conductors inside the cables creating an electric field, then using magnets in the cars to run up the cable as a linear motor. Presumably, the cars would draw power from other wires in the cable too.
What I wonder about is the limiting of the car to 200 KPH. This would make sense in the atmosphere. Vibrations would be induced in the cables by winds. Once above the atmosphere, there is no reason to limit the cars speed. It could then accelerate up to any reasonable speed. It would of course have to decelerate at the top too. But, speeds of up to 5000 KPH would appear reasonable once you are more than say 150 KM above ground level. It would be a comfortable trip if you kept the acceleration down to around 12 M/S^2. Changeover would be uncomfortable, as the room would seem to flip from right side up to upside down, but a simple gimbals system would make that easier to take. A quick back of the envelope calculation would give a total trip time of only a few hours. Less than the time for a subsonic transatlantic trip.
The thing would be a power hog. Existing conductors are not up to the task of the power levels that would be needed. You would probably want to power the system from both space and from the ground. The electrical coordination required would be quite interesting.
The existing nano tube fiber systems are not near the strength required for the systems yet. Nano tube fibers to date are not very long. They are also quite flammable. Yes, they will cut steel or even titanium. No need to worry about the fictional terrorists cutting the cable with an aircraft. It would take a laser. But, the cable would burn very well.
Current tether materials are more plastics with the carbon nano tubes embedded. This has the advantage of both binding the little things, and protecting them from the oxygen. This approach has yielded tethers of over a kilometer in length. But, the strength is only a little better than steel. Much work remains to be done on tether materials.
The Space Elevator will need something that can be responsive to vibration dampeners in the atmosphere, resistant to impacts from orbital debris, as well as resistant to UV radiation and cosmic rays. It would also have to have better bonding of the carbon nano tubes into the matrix, and be able to increase the amount of nano tubes in the matrix. It's an interesting materials problem.
Progress is being made though. The sort of material needed will be useful for many construction projects here on Earth too. It will be a wonderful tension member. It can provide great compression strengthening too by having a non compressible material inside a wrapping of this material. Tether wrapped concrete columns would enable mile high buildings to be much lighter. It would enable much longer bridge spans. It would also enable structures that are not currently possible.
The biggest hurdle to developing the basic system is to be able to reliably produce the long strands of carbon nano tubes for inclusion in the matrix.
The material for the power wiring is another fascinating area for consideration. a room temperature superconductor would be ideal. A material that doesn't super-conduct might be necessary, but I would want a material with lower resistance than copper wire.
All of these details are why Aurthur C Clark said it would take 50 years after people stopped laughing before it was done. they stopped laughing 5 years ago.
What I wonder about is the limiting of the car to 200 KPH. This would make sense in the atmosphere. Vibrations would be induced in the cables by winds. Once above the atmosphere, there is no reason to limit the cars speed. It could then accelerate up to any reasonable speed. It would of course have to decelerate at the top too. But, speeds of up to 5000 KPH would appear reasonable once you are more than say 150 KM above ground level. It would be a comfortable trip if you kept the acceleration down to around 12 M/S^2. Changeover would be uncomfortable, as the room would seem to flip from right side up to upside down, but a simple gimbals system would make that easier to take. A quick back of the envelope calculation would give a total trip time of only a few hours. Less than the time for a subsonic transatlantic trip.
The thing would be a power hog. Existing conductors are not up to the task of the power levels that would be needed. You would probably want to power the system from both space and from the ground. The electrical coordination required would be quite interesting.
The existing nano tube fiber systems are not near the strength required for the systems yet. Nano tube fibers to date are not very long. They are also quite flammable. Yes, they will cut steel or even titanium. No need to worry about the fictional terrorists cutting the cable with an aircraft. It would take a laser. But, the cable would burn very well.
Current tether materials are more plastics with the carbon nano tubes embedded. This has the advantage of both binding the little things, and protecting them from the oxygen. This approach has yielded tethers of over a kilometer in length. But, the strength is only a little better than steel. Much work remains to be done on tether materials.
The Space Elevator will need something that can be responsive to vibration dampeners in the atmosphere, resistant to impacts from orbital debris, as well as resistant to UV radiation and cosmic rays. It would also have to have better bonding of the carbon nano tubes into the matrix, and be able to increase the amount of nano tubes in the matrix. It's an interesting materials problem.
Progress is being made though. The sort of material needed will be useful for many construction projects here on Earth too. It will be a wonderful tension member. It can provide great compression strengthening too by having a non compressible material inside a wrapping of this material. Tether wrapped concrete columns would enable mile high buildings to be much lighter. It would enable much longer bridge spans. It would also enable structures that are not currently possible.
The biggest hurdle to developing the basic system is to be able to reliably produce the long strands of carbon nano tubes for inclusion in the matrix.
The material for the power wiring is another fascinating area for consideration. a room temperature superconductor would be ideal. A material that doesn't super-conduct might be necessary, but I would want a material with lower resistance than copper wire.
All of these details are why Aurthur C Clark said it would take 50 years after people stopped laughing before it was done. they stopped laughing 5 years ago.
Edited by YetAnotherBob
Updated - 29th Feb 2012