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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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Orbital Towers
By wordsworm on 1/6/2009 1:49:37 PM , Rating: 3
I always preferred the term 'orbital tower' to 'space elevator.' Somehow the latter term connotes bad music on the world's longest elevator ride. Who here would want to listen to Avril Lavigne music at 1/2 speed played on a synthesizer for an hour?

What I don't understand about this whole issue is why they figure the energy in sending ships to space is an issue. As far as I know, the earth's rotation provides all the energy they need to get out. I understand that from the base to some point energy needs to be used, but after that point that energy could be recouped by adding magnetic generators at the end point which would siphon off the energy from the goods at the end of the launch. The longer the launch, the more force would be applied to the goods being launched.

RE: Orbital Towers
By Alareth on 1/6/2009 3:17:02 PM , Rating: 2
I prefer the term skyhook.

RE: Orbital Towers
By Rivenburg on 1/6/2009 4:02:11 PM , Rating: 2
hey someone with a brain AND an education.

Yes after midpoint the centripetal force would propel you out & slowing down would be an issue.

what most people miss about this structure is that it WONT BE PRIMARILY FOR GETTING INTO SPACE.
It will primarily be a superconducting power link to the earth from a massive ring of solar sats at the 26000 mile Geo-sych point.

Power for the climbing wont be an issue, just grab a tiny piece of the insanely intense electrical field a few meters away via magnetic field it will generate. Super conducting materials allow almost NO penetration of themselves by magnetic fields thus they would have one from this powerful a current on the outside of the cable.
In a real life space tower, powering the lift wont be a problem.

Now lets discuss the movement of a 26000 mile long cable massing more then several cities worth of sky scrapers.
BZZZT, non-starter. The energy involved is insane. Complete power loss on each stroke up in the gigajoules range. This will turn to heat at some point & be a real mess.

The only way to use this method is to have a VERY small secondary cable to vibrate up & down AND it has to be powered from the space end so it's pulling not pushing. fortunately thats where all the free power is.

chances are the midpoint will be a station that allows the car to be reversed for the second half of each trip to keep the appearant local "down" on the floor and to control the climb/decent.

RE: Orbital Towers
By masher2 on 1/6/2009 5:24:59 PM , Rating: 2
> "I understand that from the base to some point energy needs to be used, but after that point that energy could be recouped"

True-- but that point is geosychronous orbit, 35,000 km straight up. The energy required to do that is quite considerable, and can be calculated straight from the old PE equation, u=mgh.

RE: Orbital Towers
By wordsworm on 1/7/2009 3:50:03 AM , Rating: 2
OK Spock... I mean Mash, for the sake of fun old physics math which isn't one of my abilities, how much longer than 36mm would the orbital tower have to be to recoup the energy required to launch? Instinct tells me that even at 1km, we'd be talking about some serious speed. Consider that a good sling can propel a rock fast enough to brain Goliath.

From what I understood, any orbital tower at all would require a length greater than 35.7mm anyways, just to keep it up. So, I don't know how many more km/mm would be required to recoup the energy used to launch a kg into space, I'm sure it's significant.

RE: Orbital Towers
By masher2 on 1/7/2009 11:36:58 AM , Rating: 2
For a precise figure you need to write an integral, which I outlined a few posts up. But if all you want is a "free ride", there's a much simpler way. The energy you expend on the way up can be recovered on the way down through regenerative braking (the same tech used on hybrid cars). You'd need a godawful massive battery to store the energy, but in theory at least its possible.

Now, if you want to use the elevator for launches beyond earth orbit, you simply build it beyond geosynch and use the excess dV to launch. One 150,000 km long, for instance, would give you a free ride to anyway in the solar system, if you're willing to use slow Hohmann-transfer trajectories at least.

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