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European Space Agency engineer Age-Raymond Riice as developed a remarkably simple way to propel a space elevator upward with a series of rhythmic jerks.  (Source: BBC)
A new method could help realize dreams of a space elevator

A space elevator has been a long standing dream of many in the science and tech community.  Conceived by Russian scientist Konstantin Tsiolkovsky in 1895 and popularized by author Arthur C. Clarke, many believe the idea holds a great deal of real world promise, and may eventually provide the cheapest way to transport people and goods into space.  With many countries such as Japan, the ESA, and the U.S. finally getting serious in a race to become the first nation to develop a space elevator, enthusiasm is at a high.

Unfortunately, though, much of the materials and methods needed to build such an elevator are infeasible.  While carbon nanotubes could allow for a cable strong enough to hold a space elevator in theory, one key problem is how to propel the elevator along the cables into space.

Among the previously suggested methods of powering the climber into space were beaming microwave or laser power, or even concentrated solar power to the climber; but all these efforts have a long ways to go before being close to being feasible.

However, a remarkably simple idea proposed at the Second International Conference on Space Elevator and Tether Design in Luxembourg could hold the key to powering the space elevator.  European Space Agency ground station engineer Age-Raymond Riise showcased a remarkably simple propulsion method which uses a series of rhythmic jerks to propel a device upwards along a taut cable.

For his demo he tied brushes with their bristles pointing down, representing the elevator cabs around the broom stick, representing the elevator cable.  As the brushes pointed downward, they required less force to slide up than to slide down.  The assembly slid up and down along the broomstick, but experienced a net upwards motion, slowly climbing to the top of the broomstick.

The novel new method holds great promise as similar jerking motion could be applied to raise the elevator on a full-sized design, in theory.  The key technical challenge would be designing a cable strong enough to withstand the heat and forces exerted on it by the atmosphere. 

However, advocates argue that with payload costs still remarkably high, the financial and social incentives for building a space elevator are enormous.

Building a space elevator could enable novel new industries.  Describes Benoit Michel of the Catholic University of Leuven, a conference attendee, "From my point of view, the space elevator project is important because it enables a far more directly useful project - installation of large space solar power satellites around the Earth to provide continuous, cheap, CO2-neutral, environmentally friendly energy.  I firmly believe that the next century will have a large space-based industry and that industry will be the main energy provider for the whole mankind."

Mr. Riise has been approached by commercial aerospace terms about his idea and is in talks with them over terms.



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RE: A bit misleading
By masher2 (blog) on 1/7/2009 10:25:35 AM , Rating: 3
quote:
I don't really understand wiki's article on it, and my likely erroneous guess is that the equation would be F=d/dt(mv), which is complicated by the decay of F as the object gets further away from the gravitational effect of the earth.
You need a bit of basic calculus to do the equation. You combine an expression for the mass of the cable at any point (which would be a constant for a linear cable, but in reality would taper at both ends) with the expression for gravitity at a given point (GM/r^2), and the term for centripedal acceleration

Then, you integrate over the range from altitude 6,000 (earth's surface) to 42,000 (geosynch), and equate that to whatever range of integral gives you the same value from 42,000 to x, x being the length of your cable past geosynch.

You can do it in a single step by just requiring the total force on the cable to be zero, and finding the appropriate rnage of integration, but it may be a little easier to understand in the two-step process I outlined above.

To be truly accurate, you need to take in additional terms such as atmospheric drag, the fact the earth is actually an oblate spheroid, etc, etc.


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