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Carefully Timed Jerks Could Power Space Elevator
Hugh Pickens writes "BBC has an interesting article on the long-standing issue of how to power the 'climber' that would ascend a space elevator into space. Previous ideas have included delivering microwave or laser power to the climber beamed from the Earth's surface, but now European Space Agency ground station engineer Age-Raymond Riise has demonstrated a device that could provide a "lift into space" for cheaper space missions along a 100,000-km long tether anchored to the Earth. Riise demonstrated sending power mechanically by providing carefully timed jerks of the cable at its base with a broomstick to represent the cable held in tension, an electric sander to provide a rhythmic vibration to the bottom of the stick, and three brushes representing the climber with their bristles pointing downwards allowing the climber assembly to slide upward along the broomstick as it moved slightly downward, but grip it as it moved slightly upward. 'It would be possible to make a suspension system that completely decouples the cabin where the passengers are,' says Riise. 'For them it would be a linear movement with very little disturbance.' Riise says that he has been approached by commercial elevator companies, who are researching new ideas for elevators in superscrapers where the simplicity of the approach makes it attractive when compared to other ideas for powering lifts, such as compressed air."
This is not flamebait - its a classic seinfeld episode: Synopsis full episode.
For every 'yank' performed on the cable, you pull the anchor lower in orbit.
This is wrong - the transmitting end (ground station) can and would "push" just as readily as it would "pull". Then the vehicle would absorb this wavefront as it converts it to potential energy, such that there is very little energy propagating past it up the cable. You have to consider that this cable is very very long, and at such a scale it becomes more like a slinky, or a piece of string with a cup on each end.
Your assuming that the cable is rigid... most designs for this that I have seen are usually a ribbon/cable that can flex in either one or two dimensions. This would mean that you could not push it, only pull.
Also, we are having enough trouble creating a cable that can withstand the incredible force required for a simple tether... now they want to add vibration on purpose? This has disaster written all over it.
Some days I get the sinking feeling Orwell was an optimist.
No, there is no necessarily a need of providing energy for the anchor in space regaining its 'orbit'.
Say the height for the center of gravity of "cable + anchor" was that of the geostationary orbit, call it H. At that point, the cable needs null force applied on its attachment to the Earth surface, it's in balance. Say now you place that center of gravity at H+10%. Now the cable needs tension on its attachment to Earth's surface, the anchor is willing to go, cause by effect of having it attached to a point in the surface you make it turn geostationary, i.e., faster than the speed of the orbit that belongs to its height. Now, you 'jerk' on the cable, reducing heigth to H + 5% . You are still on the 'want to go away' side, meaning if you release the cable, if will go again as high as you let it go.
Is like a cord hanging all the way down from a hot air balloon. You make a bunch of people pull down the cord, the balloon goes down, but once all of them release, the balloon goes up again. Imagine you do that over and over. A clever mechanism ('lift') that dettaches itself from the cord (while not losing much height) during the pulldown cycle, and attaches firmly to the cord during the release cycle, will effectively climb up to the balloon.
For sure all this reasoning is not accounting for the atmosphere, anyway..
Actually, the elevator works fine from a suspension point of view. You just need a balancing mass past geosync altitude (which could be just more cable with a balancing mass and moving vibration dampers). There are questions about how to deal with tangential Coriolis forces from cars going up the elevator. Maybe you might be able to partially balance it with giving the elevator cars a really big charge and a really good capacitance skin so that electrical force from travelling through the Earth's magnetic field balance out the Coriolis force on average?
Laissez lire, et laissez danser; ces deux amusements ne feront jamais de mal au monde. - Voltaire
It's worse than that actually. The distance to Geosynch is 36000 km. Moving at a 100 km/h (about 55mph) you'd still be underway for 360 hours. There's no way any climbing-mechanism that depends on mechanical transfer from the ribbon will be able to climb even close to fast enough to make the thing practical.
The demonstration shows a climbrate of around 0.1m/s at which speed it'd reach geosynchornous orbit after about 15 years of climbing. Dumbest idea ever.