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Future of Space Elevator Looks Shaky
lurking_giant writes "In a report on NewScientist.com, researchers working on development of a space elevator (an idea we have discussed numerous times) have determined that the concept is not stable. Coriolis force on the moving climbers would cause side loading that would make stability extremely difficult, while solar wind would cause shifting loads on the geostationary midpoint. All of this would likely make it necessary to add thrusters, which would consume fuel and negate the benefits of the concept. Alternatively, careful choreography of multiple loads might ease the instability, again with unknown but negative economic impacts."
The engineering required for this elevator is mind boggling. After witnessing the amount of time and effort that went into a small suspension bridge spanning the river Thames in London (The Millenium Bridge), the mere idea of this elevator scares the shit out of me.
Why not compensate for Coriolis force by using rockets?
Coriolis force is tiny, so we won't need a lot of reaction mass.
Probably, it can be used together with multiple loads choreography for greater effect.
Nobody said this would be easy (quite the opposite), and nobody is claiming we're even close to being "there" yet. But is the space elevator dead? No. Just still working out the kinks. Look, have you any idea of the number of launches required to prepare, by tiny increments, for the eventual (and still debated, snicker) moon landing? We'll get there, eventually.
Even with thrusters, it's bound to be a better long-term solution than rockets. Especially using ion drives, you could hard-wire the fuel supply from down below, so to speak, and so not need to haul that mass, too.
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When it came down to it the space elevator though nice, is a dumb idea. Like the jet pack. Think if the resources needed to defend it from terrorists, or maintenance costs. Seemed also like a put all your eggs in one basket as well I mean we would be much better off to just improve our propulsion ability. Personally i like a rocket powered mag-lev launch vehicle, that would travel down a rail that ends up pointing to the sky.
I wonder how large a no-fly zone would be required for a space elevator? After all, just imagine the damage it might cause if the thing were to collapse and land over a populated area.
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I agree with your assessment of their stated problem, but I'd like to know where they got that idea in the first place. Launching directly from the space elevator has never (in my understanding) been part of the concept. Instead, cargo (+ people) is offloaded at a station and is moved into a shuttle. The shuttle detaches from the station and then applies a thrust vector to move away.
The point of a space elevator is not to launch items directly into space, but to create a more efficient, higher through-put method of getting people and equipment out of the Earth's gravity well.
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Most of the inner planets have no space elevator at all; Venus and Mercury because their days are unfeasibly long, Earth because its gravity well and debris belts challenge the limits of engineering.
Look where all this talking got us, baby.
Corrolis force problems were one of the first things I thought of when I first heard about the space elevator, but I'd never seen the issue brought up.
It's a given that a elevator would be tethered at the equator, thus will be traveling at 1600kph, the velocity of geosynchronous orbit is what, 11000kph? Anything climbing from the bottom up will be accelerated to that as it ascends. So the question is how the hell do you mitigate this without literally bending the thing out of shape - burning fuel is silly It's not a trivial velocity, it's 40% of what would put you into LEO orbit anyway!
Despite this, I don't think this is a showstopper, remember Arthur C Clarke told is it will be built...
After logging in slashdot still does not take you back to the page you were on. It's been that way for 20 years.
Why not went air thorugh the tube to as a correction mechanism? No need for rocket fuel in a structure reaching up from the ground, just blow air. Hell, we even do need air up there for life support and other things. Air supply could even be used to produce rocket fuel in space.
Very amusing indeed.
Especially since Kim Stanley Robinson wrote his "Red Mars" series & specifically addressed these issues. He correctly identified the problems, and came up with very realistic solutions.
Yes, the orbital section had to have thrusters to combat what is mentioned in the article.
He also determined that the 'elevator' portion would require significant advances in materials, and require a futuristic substance that could withstand the sheer loads & twisting due to wind, atmosphere, etc.
He even took it to the point of examining what happens when the terrorists from Earth blow up the link cable that connected the orbital portion, resulting in the elevator 'crashing' down to Mars. He even correctly showed how it would actually wrap around the planet (as opposed to falling straight) and when the final piece impacted it caused a huge crater from the sheer kinetic energy. (like a whip-lash).
Good stuff. Maybe these 'scientists' should bother to read once in a while, they might save themselves quite a bit of time. Of course, that would mean budget reductions, so they probably wouldn't have bothered anyhow.
I told everyone it wouldn't work. But would they laugh at me? No!
I know you were joking, but I really think it won't work for reasons not specified in the article. It's such a simple reason that I can't believe it's so rarely mentioned or addressed.
The earth is built very much like a capacitor. The ground has a fairly strong positive charge and the ionosphere has a fairly strong negative charge, with an insulating layer of air in-between. Carbon nanotubes can conduct electricity; so can most other materials I have heard of that would be used for a space elevator. I imagine that any conductor (and possibly dielectrics also when you consider electrical breakdown and the sheer current involved) would vaporize as soon as this circuit is closed. Coriolis forces and weight distribution and whether thrusters would be necessary seems trivial by comparison.
It is a miracle that curiosity survives formal education. - Einstein
If the reason for coming with such a thing as a space elevator(which I agree is pretty impossible with any material currently known) is to cut down on the cost of getting things into space then why hasn't anyone been looking to build a "supergun" like Gerald Bull had experimented with ages ago? It just seems logical that if you built it at the equator you could cut down on fuel required by using a gun style launch and then having the thrusters kick in at the top of the arc and use the momentum to assist getting the vehicle into space. And if we could build it as a magnetic coil or rail gun we could save even more by using electricity, which is easier to produce, than chemical engines.
So is there anyone looking at the "supergun" concept? or did the idea die out with Bull?
ACs don't waste your time replying, your posts are never seen by me.
The system will need to send electrons to the surface constantly, creating a massive current on a 32,000 mile line. Even if you J-Hook the thing over the point and bring it back into the atmo, it is going to make a mess.
We are better off using this nano-reinforced material to either a) create a 1km wide column that is devoid of atmosphere (and hence no resistance) or b) create a 1km volume capable of containing vacuum, as per Diamond Age, creating the lightest possible lighter-than-air vehicles to SSTO.
kulakovich
The earth is built very much like a capacitor...
So use the current flow. You're breaking the earth's magnetic field lines with the cable. Not a lot of field strength, but it's a lot of field, sounds like a generator to me. Ship up the necessary kilograms of (i don't know, zinc perhaps) sacrificial anode and dump the potential via ions accelerated as lateral thrusters running continuously, and vary the flow in any particular direction to adjust the position of the cable terminus. The spare current could run the elevator cars.
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Science fiction writers might not have much education or knowledge of physics or even reality, however they have often been way ahead of their time with their ideas. Handheld communication devices, cell phones, space travel, lasers, robots, virtual reality, "smart wheel" cars, x-ray technologies, etc. are all examples of how science fiction became science reality.
People who don't know, or who refuse to accept that things are 'imposible'. They're the ones who drive progress. Think the Wright brothers, Einstein or better still Michelangelo, who imagined flying machines and submarines that were only inviable because the necessary technology (engineering & materials) were not available.
After all, geosync orbits were thought up by first by a scifi writer...but to your point, Arthur C. Clarke did have a good grasp of Physics...
A concern with talking about the efficiency of rockets is that you have to carefully define what you mean: normal chemical rockets have extremely high Carnot efficiencies, mediocre mass and energy efficiencies. A space elevator doesn't have a Carnot efficiency, has terrible mass efficiency, but extremely good energy efficiency. An ion thruster has no Carnot efficiency, has great mass efficiency, and terrible energy efficiency.
Now consider something like a gaseous-core nuclear rocket (fission, with the core so hot it's gaseous): high Carnot efficiency, high Isp so high mass efficiency (near ion engine's), and pretty good energy efficiency.
It just has this one slight problem...
-- Alastair
The space gun concept would really only be good for a very narrow range of payloads that can withstand the extreme g-forces produced by such a device. You can reduce the g-forces by using a longer barrel but it's still a concept that really isn't feasible.
What we should be looking at is a Space Fountain. Yes, it seems like a very odd idea but it's backed by a lot of very good science and a lot of people are saying that it can be done with present materials and technologies. At the very least we should be experimenting with them on a smaller scale, using them to erect temporary masts and towers.
Sapere aude!
Start with the space shuttle's tethered power generation experiments: http://www.phy6.org/earthmag/wtether.htm
Multiply the power generated by the many orders of magnitude that the elevator is longer than the tether was.
As the elevator swung through the magnetosphere on the aposol and perisol points of its rotation, it'd be generating billions of volts and conducting huge amounts of current down to the ground and out the top end of the elevator.
The ground equipment and probably a portion of the bottom of the elevator would be turned to plasma. Same at the other end. The rest of the structure would orbit free and crash. Enough of it would not be burned away that the remainder would wrap around the Earth several times.
Note that this scenario would require it be completely built before the effect started. This is, of course, impossible. It would be burning itself away as its length was increased. Note also that this is due to the structure only, not the dynamics of something going up and down it. Nothing would ever get the chance to make the trip.
It is at first obvious that generating power in this fashion would power the elevator. Less obvious but more important, is what to do with the 99.999% of the generated power that's surplus. It's just too much surplus, and we have no technology to carry that much power safely on such a structure.
Look at the details of the tether experiment. Less than 20 km of tether produced 3500 volts and burned the tether away from the shuttle. The elevator would be 4216 times longer. Also, the tether was not directly vertical, whereas the elevator would be. The amount of power generated would be more than the 4216 times the length.
A primary choice for the elevator structure is carbon fiber. When that stuff burns it puts out a cloud of random buckytube-like particles which pose a health hazard much like a cloud of equivalent mass of asbestos. The best choice of material for the structure would be pretty near the worst choice when it came to its inevitable self-destruction.
If the elevator burned away in the atmosphere, the carbon particulate would be a nasty pollutant. If the structure boiled itself away at higher altitude, outside the atmosphere, it would leave a trail of carbon particles that would become a hazard to spacecraft. Flying through that cloud would be like plowing into fine sand. A brief encounter would be very little trouble. But trying to fly at that same orbit for an extended time would erode away the spacecraft. If it were dense enough, it could also collect some charge in the manner of the tether, and discharge that into a spacecraft approaching it.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
Engineering satellites and probes to withstand high G-forces will probably be easier than building a Space Elevator. Or Space Fountain.