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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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A bit misleading
By masher2 (blog) on 1/6/2009 8:43:01 AM , Rating: 6
What Jason doesn't mention in this article is the true appeal of the approach. Rather than other methods suggested which require the climber to either carry its own power or have motive power beamed to it, this method uses the cable itself to transmit power mechanically. The power is applied vibrationally at the cable base; the result at the climber is the series of "rhythmic jerks".

An interesting idea, for sure. As I see it, though, its going to suffer a very low efficiency due to damping losses in the cable itself.




RE: A bit misleading
By nosfe on 1/6/2009 8:46:19 AM , Rating: 2
yep, that's the first time i see jerks put to good use


RE: A bit misleading
By Samus on 1/7/2009 2:57:26 AM , Rating: 2
quote:
yep, that's the first time i see jerks put to good use


Silly...all jerks are put to good use. Their very existence is innocent, unless, of course, there is something better to do.


RE: A bit misleading
By Dreifort on 1/6/2009 11:47:33 AM , Rating: 2
I read the article thinking something completely different (and not related to Austin Powers).

I thought they were talking about elevators in space stations, lol. But I quickly understood they were talking about elevators from earth's surface.

My question is, what practical use would this serve? Other than building one at Disney Land and charging $500 per ride?

You couldn't connect this to anything on the other end...wouldn't earth's rotation or gravity pull it apart from the connection?


RE: A bit misleading
By masher2 (blog) on 1/6/2009 3:04:14 PM , Rating: 3
I'm not sure why you were rated down for asking a simple question, but the entire idea of the space elevator is for it to be strong enough to resist both the centripedal pull of rotation and its own weight. Stretch it out past geosynchronous orbit and attack a massive counterweight to it...it then becomes a permanent, free-standing structure.


RE: A bit misleading
By Dreifort on 1/6/2009 4:08:04 PM , Rating: 2
ppl hate me for obvious reasons ;) (politics)

but will this be used to: launch satellites? repair satellites? dock with space stations/shuttles?

I can see it taking longer to maneuver a dock connection to an earth fixed asset than it would be to launch a shuttle and do a mid-flight dock.


RE: A bit misleading
By masher2 (blog) on 1/6/2009 5:18:47 PM , Rating: 2
It would be used to launch anything, at a (potential) cost of pennies of electrical power per pound, rather than the $10,000 or so it currently costs. That would open up the entire solar system to manned exploration (and exploitation) as once you're in orbit, you're halfway to anywhere, as far as total energy (dV, to be precise) is concerned.

As for docking with a space station, the cable's endpoint would itself become a station, one that would eventually become an entire city in space.


RE: A bit misleading
By Dreifort on 1/7/2009 9:51:45 AM , Rating: 3
(and because I saw the documentary about this last night) what about discharges in the air - lightning? wonder how they would pull the charges away from the cable?

I know this is the theorized culprit to the shuttle disaster in 2003. NASA wasn't sure how to handle the charges then - will they ever?


RE: A bit misleading
By mcnabney on 1/6/2009 8:54:19 PM , Rating: 3
There are two great challenges to the space elevator.

1. The cable. Even if the silly thing could be made, could you imagine how it could be conceivably put in place?

2. The counterweight. There is a great lack of million ton chunks of something in geosynchronous orbit. That means we have to launch it in pieces by rocket (at $10k a pound we are going way over the planets annual GDP) or find some way to wrangle an asteroid. Do you trust NASA to bring what could be a planet-killer close to Earth?

I don't see either of those tasks being accomplished until we enter a new age of technology.


RE: A bit misleading
By masher2 (blog) on 1/6/2009 10:21:09 PM , Rating: 3
> "Even if the silly thing could be made, could you imagine how it could be conceivably put in place?"

Put a cable factor in geostationary orbit; drop down an ultrathin fiber. Use that fiber to pull down sucessfully thicker strands.

> "There is a great lack of million ton chunks of something in geosynchronous orbit. "

If the cable is extended an equal distance past geosych, it obviates the need for a counterweight entirely. Furthermore, the counterweight could easily start small and all but the intial seed be driven up the cable itself, meaning it wouldn't need to be launched by rocket.

Finally, even a million-ton asteroid is far from a "planet killer". Those are more in the trillion (a million million) ton range.


RE: A bit misleading
By wordsworm on 1/7/2009 4:16:03 AM , Rating: 2
quote:
If the cable is extended an equal distance past geosych


I don't think you'd need an equal length past geo-synch. The distance past geo-synch. I believe that we're looking at exponential rather than linear. We're talking a centrifugal force. 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.

Are there any physics experts here that can give a rough calculation on a kg?

In any case, I took a look around for some information, and didn't really find anything that helped me. However, another website asked the question, "What would happen if the orbital tower snapped? http://gassend.net/spaceelevator/breaks/index.html Bloody good question. I can't even begin to guess what kind of damage it would do. I think it's a good enough question that might make people stop laughing at the idea of an orbital tower.


RE: A bit misleading
By EODetroit on 1/7/2009 10:11:51 AM , Rating: 2
Anyone do the math on what happens if the cable snaps, maybe even altering the altitude of the break for the worst case scenario? Would the "top floor" be tossed out of earth orbit (a death sentence for the people on board), for example, or would it naturally settle into a higher orbit that is presumably recoverable?


RE: A bit misleading
By EODetroit on 1/7/2009 10:13:03 AM , Rating: 2
LOL jeez its in the post directly above this... I just didn't read quite far enough.


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.


RE: A bit misleading
By Cerberus90 on 1/12/2009 4:59:01 PM , Rating: 2
Thats not how they'd do it, you get a really long reel of the carbon nanotube cable, and attach one end to a rocket, and have that tow it into space.

:D :D :D


RE: A bit misleading
By Tyndel on 1/6/2009 12:05:09 PM , Rating: 2
However, what is the feasibility of moving that much mass up and down to gain a few feet/yards of upward movement per convulsion? How high up does the climber have to be before the vibration is changed to convulsion?

It seems, to me, to put some major strain on the anchor and would mean the other end of the cable couldn't be attached to a semi fixed location like a space station held in place a large part by centrifugal force canceling some of the gravity playing on the cable itself.

While any sort of cable based space elevator would require some room for play at the base, I would think a car running on tracks up the side like a train would be more feasible. Though if this were possible there would be very little to limit the size of the load that could be transfered upwards once it did get to the convulsion stage.


RE: A bit misleading
By masher2 (blog) on 1/6/2009 3:02:26 PM , Rating: 4
> "I would think a car running on tracks up the side like a train would be more feasible"

What do you power the car with? If you carry your own chemical fuel, you're back to the rocket equation, and the incredibly poor fuel-to-payload ratio thereof. You could try beamed power if you can deal with the focusing, generation inefficiencies, and atmospheric absorbtion issues, or you can try to carry a nuclear reactor aloft with you. That's about your only options.

This is a fresh new approach. Quite probably impractical...but still valuable for consideration.


RE: A bit misleading
By Reclaimer77 on 1/6/2009 4:43:00 PM , Rating: 1
The whole idea of the space elevator in itself is a crock. This approach is like trying to perfect a better screen door for a submarine.


RE: A bit misleading
By Sanity on 1/6/2009 5:30:51 PM , Rating: 3
Well as soon as you perfect a safe anti-gravity drive that can get us into orbit, and runs off of 6 AA batteries, let us know.

And your analogy is a crock. 0.o


RE: A bit misleading
By Tyndel on 1/6/2009 5:32:50 PM , Rating: 2
Seems to me electricity would be the most obvious solution. Beaming either microwave or laser is just too inefficient.

One of the advantages one could expect from having a space elevator and station would be a cheap efficient way of sending converted solar energy to earth without having to use beaming at all. And if we are already generating electricity at the top and sending it down why not just use, that, to power the climbers?

We are likely, as close to an ambient temperature superconductor(currently ~212K), as we are to the tinsel strength required to hold a space elevator together.


RE: A bit misleading
By masher2 (blog) on 1/6/2009 5:46:27 PM , Rating: 2
> "Seems to me electricity would be the most obvious solution."

Work out the weight of 35,000 km of high-power cable and insulation. Added to the tower, that's a substantial consideration. Also, the line losses over that length are astronomical. There's a reason most power plants are within a few hundred miles of the areas they serve.

Still, some combination of ultra-HVDC transmission and possibly using the cable itself as a conductor might turn out to be feasible.


RE: A bit misleading
By albundy2 on 1/7/2009 3:57:31 PM , Rating: 2
cnt's are conductive correct? cnt's are also the only trully feasable material to construct the cable correct?
iirc cnt's are also one of the best, if not the best electrical conductor. [i beleive i read that here, in a past article.] it would then make the most sense to use the cable as the/an energy source.

i was thinking while reading this article, why not use a helium baloon to power/assist the first few miles up. it would at least shed some weight until the atmosphere, wind or whatever negated the benefit.


RE: A bit misleading
By Gestahl on 1/14/2009 3:24:02 AM , Rating: 2
While CNT's may be conductive, and one day made strong enough for such a project... this isn't the case just yet. When claims are made about strong materials for structural applications, they seem frequently to neglect the elementary science of scale. Just because it is possible to produce a nanotube of carbon which has a calculated strength of 130 GPa and a measured strength approaching that value, it does not mean that this can be translated into a fibre of a length visible to the naked eye, let alone the 120,000 km needed to begin thinking about a space-elevator. Estimating a cable material with a tensile strength/mass ratio of at least 130 GPa/(1300 kg/m^3) would be required to support such dreams.

Assuming we do find a material with a tensile strength strong enough to support itself across the vast distance from surface to <geo orbit, there are other issues that come into play. Corrosion is a major risk to any thinly built tether (which most designs call for). In the upper atmosphere, atomic oxygen steadily eats away at most materials. A tether will consequently need to either be made from a corrosion-resistant material or have a corrosion-resistant coating, adding to weight. While there are known materials (such as gold and platinum which are practically immune to atomic oxygen... or a more common metal such as aluminum which is damaged very slowly, could be repaired as needed)

Also we have the effectiveness of the magnetosphere to deflect radiation emanating from the sun decreasing dramatically the further away from the surface the tether/cable/tower is. This ionizing radiation may cause damage to materials within both the tether/cable/tower and climber(s).

Until these issues can be resolved, while pulling together the many other variables, the dream of a space elevator is nothing more than that, a dream to science geeks (myself included).


RE: A bit misleading
By wordsworm on 1/7/2009 4:41:48 AM , Rating: 3
quote:
If you carry your own chemical fuel, you're back to the rocket equation, and the incredibly poor fuel-to-payload ratio thereof.


Something to make up for my Texan bashing - think "nuclear powered car". Can't really make a rocket that uses nuclear thrust, but since climbing an orbital tower would require mechanical energy it would be quite 'easy' to utilize nuclear power to send something into orbit.

I still prefer the idea of using maglev space launches. Surely it would be cheaper. You only need about 4mm of track, and if you could launch it 10km from sea level, a lot of the issues of friction (with the rest of it being encased in a vacuum) could be addressed. I can't help but think it would be a heck of a lot safer than an orbital tower to boot.


RE: A bit misleading
By jlips6 on 1/8/2009 4:57:14 PM , Rating: 2
perhaps this is just me displaying my ignorance, but why not use an improvised version of a counterweight system? line going down one side, then the opposite side.
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|( )| i mean, it is an elevator after all...
|( )| and dailytech also messes up ascii pictures. grr.
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RE: A bit misleading
By Amiga500 on 1/6/2009 12:56:39 PM , Rating: 2
Well, to be honest, it is a bit obvious isn't it?

I'd like to think (at least most) of the readers at DT are smart enough to realise the connotations. :-)


RE: A bit misleading
By Amiga500 on 1/6/2009 12:57:37 PM , Rating: 2
That should probably have been implications, not connotations.


RE: A bit misleading
By Dharl on 1/6/2009 12:58:36 PM , Rating: 2
Section off the elevator with a "repeater" in place. Then you wouldn't have to worry as much about tension of the cable and or loss of motion.

Of course the question then becomes: How do you section off such a device without causing any sort of interference with the motion?


RE: A bit misleading
By Sanity on 1/6/2009 2:00:49 PM , Rating: 3
Since you're being serious, I'll make a serious reply myself.

How about, when we come up with a cable strong enough, we give it the capability to expand and contract in a way that would increase and decrease the diameter of the cable itself. This would create a sort of wave that a car could ride up or down. Kind of like how our intestines push food around, but on the outside. I mean hey, if we're making carbon cables that are thousands of miles long, why not.


RE: A bit misleading
By 2uantuM on 1/6/2009 2:20:15 PM , Rating: 2
Why not just make the cable have a core made of some conductive metal (for power),surrounded by carbon fiber (and possibly some insulation, and then more conductive metal around the outside for ground? Sort of like a giant coax cable. The just cut a slit up the side so the elevator can get easy access to the power and then use a motor to work its way up.


RE: A bit misleading
By Sanity on 1/6/2009 3:29:31 PM , Rating: 2
Seems to me that just the motor added to the car would add weight you don't need. Let alone adding thousands of miles of metal in the cable itself. And sending power over thousands of miles of cable is not easy. If the elevator idea were that easy, we wouldn't be reading stories like this. We'd be reading about how over-budget the project was already.


RE: A bit misleading
By Amiga500 on 1/6/2009 3:10:59 PM , Rating: 2
Here is a thought...

Why not just use a winch?

1 guide line and 1 pulley line. The space station at the top of the elevator has to have quite a bit of mass to stay up... so stick a power plant in there (nuclear and or solar - if it would provide enough juice), attach a winch to the elevator itself, and away you go...


RE: A bit misleading
By foolsgambit11 on 1/6/2009 7:16:02 PM , Rating: 2
I imagine the fear is that, if the upper winch cable breaks.... I guess you could have emergency breaks on the car, that wouldn't add much weight.


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