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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."
I told everyone it wouldn't work. But would they laugh at me? No!
You see? You see? Your stupid minds! Stupid! Stupid!
Willy Wonka had it right. We should just be doing that instead.
You are using English. Please learn the difference between loose and lose; they're, there, and their; your and you're.
If an elevator won't work what about a space escalator?
There's also the problem that any ninja can come along and cut the cord, and suddenly you have a $500M paperweight wrapping around the earth tearing a path of destruction.
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.
The coriolis effect is not a real force. It's an illusionary effect that happens when you have a moving point of reference. As to solar winds and stuff; can you be a little less vague. Let's say for a 10 meter thick cord, white color, how much force would be imparted on the cable over its length? Is the concept currently economical? No, and that's hardly news. Is it unstable and unworkable? Well... if you're pinning your conclusions something that doesn't actually exist to answer that, I think you might have a problem.
#fuckbeta #iamslashdot #dicemustdie
No one said it would be easy.
End of lesson. You may press the button.
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.
"Good news, everyone!"
...,kind of, sort of, in Fountains of Paradise.
In that novel he proposed timing the departures of loads for a space elevator on Mars. Not to damp oscillations, in this case, but to cause them. By timing the oscillations correctly, the elevator would oscillate out of the way of the moon Phobos, which orbits lower than the Martian geosynchronous orbit.
Yep, anything 24K+ miles long and thin as a wire and zipping through the upper reaches of the atmosphere would probably be "shaky"....
The cesspool just got a check and balance.
If all goes to hell, just jump in the elevator right before it hits the ground. Problem solved.
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.
Ion drives need physical fuel as well as power... they just are a lot more efficient than traditional chemical-reaction drives. This is because they accelereate the fuel to near-lightspeed, maximizing the reactionary force per kg of fuel. (force is a combination of the mass expelled and the speed of which it is expelled... the faster the exhaust, the higher energy per kg of exhaust).
So, you'd still have to haul up fuel, just not as much as with chemical rockets.
MadCow.
I used to have a sig, but I set it free and it never came back.
if the top of the elevator isn't in geo-synchronous orbit, the elevator has to be a free-standing structure. You can only put stuff in geo-synch on the equator...
Good luck with that!
Their big objection seems to be not that the forces on the elevator are unmanageable but that oscillation could lead to payloads being released into orbits that are "10 km" too high or too low, or that the oscillation could put the elevator in the path of a satellite. Correcting that would require thrusters.
For the first, surely you could simply time your release with the oscillation, to get into the orbit you want. Even if you couldn't, the space elevator would be good for putting things in geosynchronous or interplanetary transfer orbits. The cost of a bit of propellant to correct a +- 10 km error is pretty minor compared to getting into one of those orbits in the first place.
For the second, thrusters to purposely oscillate the cable to allow it to dodge out of harms way are a pretty standard part of any space elevator proposal. That is, the ability to move the cable a little is a desired, even necessary part of its design.
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.
"In prison you just have to shut your eyes and take it. Here you have to shut your eyes and give it."
The "Space Elevators are unstable! The concept is doomed!" Slashdot summary would have been much more thrilling if there wasn't a link to the "Space Elevators are tricky! There might still need to be tiny final orbital adjustments!" New Scientist article, and even that would have been more exciting than the "Space Elevator dynamics is modeled by these stable but undamped equations! Sending multiple payloads up in the right phase causes the minor Coriolis-induced wobbles to cancel out!" Acta Astronautica article.
You people with your damn hyperlinks are ruining journalism. It's getting so a guy can't even wait breathlessly for the News At 11 anymore to find out what common household product might be Killing Our Children.
Your mind will be hyperboggled by the amount of paperwork, business trips and expense account lunches the project will generate. The engineering will look like chump change.
They whose government reduces their essential liberties for temporary security, receive neither liberty nor security.
OK... what if we built this large wooden ladder...
Of all of the technical and political roadblocks to building a space elevator, both of these seem quite minor in comparison. This is kind of like saying "I was going to bench press this Hummer H2, but since you added a fuzzy steering wheel cover it's going to be completely impossible now."
I read the internet for the articles.
This idea has it's ups and downs.
Operator, give me the number for 911!
From Wikipedia:
The first failure resulted in the deaths of three astronauts, Gus Grissom, Ed White and Roger Chaffee, in the Apollo 1 launchpad fire.
Putting moderation advice in your
In all seriousness, the space elevator gets a lot of press because it's the concept that is easiest for the average person to understand, that doesn't mean it is the only option (or even the best option) to efficiently get stuff into orbit without rockets. I always thought the launch loop made more sense (http://en.wikipedia.org/wiki/Launch_loop/).
The idea is that the moving parts are what keeps the structure stable, rather than tension or compression. In theory it could be built with today's materials and technologies and could be cabable of launching more into orbit in its first month than has been launched to date with conventional rocket launches.
Then of course, there are the non-traditional rockets such as laser propulsion, where a laser is shined up from the ground to superheat the air in the rockets cone, which, in turn, produces thrust. And of course, my personal favorite, there's always Project Orion. Not the wimpy one NASA is using to get to the moon, I'm talking about the original Project Orion. As in, using thermonuclear bombs to launch a city sized spaceship into orbit.
Comment removed based on user account deletion
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.
A rotating skyhook (a rotating line connected to a ballast on one end and a payload on the other) wouldn't have that problem.
http://www.nss.org/settlement/L5news/1983-skyhook.htm
But a rocket hook combination makes the most sense right now, it would reduce the launch weight by removing the need for the vehicle to accelerate itself all the way to orbital velocity.
[-- Trust the Monkey --]
Coriolis force as a show stopper? Well, given that:
... let's just say I wouldn't be holding my breath waiting for the space elevator. Unless we can solve the problems involving manufacturing of carbon fibers with the appropriate properties (which is far from a sure thing), worrying about issues like Coriolis on the ascending climbers is like discussing how many angels can dance on the head of a pin.
ITYM: http://en.wikipedia.org/wiki/Launch_loop
So much wrong, so little time...
Sorry, most of your post is factually challenged.
1) Space elevators do not lower the energy required - they just use the energy differently.
2) They do not take you to where the gravity is weak - they take you to the point where the force of gravity (which is essentially unchanged) is balanced by centripetal force (which, being linked to w^2r goes up linearly with distance).
3) Rockets typically take you to about 7.7 km/s (orbit), not 11.2km/s (escape).
4) The energy given to the satellite (assuming the same final orbit) is identical regardless of the launch vehicle/elevator used. What is different is the energy efficiency of the system in putting energy into the satellite:
A rocket sends lightweight propellant in the opposite direction very fast in order to transfer the energy. An elevator sends a huge mass (essentially the entire earth) very slowly in the opposite direction. Since momentum is conserved, the mass x velocity of both systems is the same - but since the Earth masses a lot more than most rockets, the Earth's relative velocity is far lower. This is where the e=0.5*m*v^2 comes in - the "wasted" energy is the energy provided to the Earth or propellant. Earth has a small v, big m - which works better than the rockets big v little m.
So you always have to give the satellite the same energy - there are just different efficiencies of giving it that energy. Space cannons have the problem of needing to give that energy extremely quickly... very difficult indeed.
while (sig==sig) sig=!sig;
Speaking of which, there is an airship to orbit concept that was discussed here a few years ago.
You have two airships, a ground ship and an orbital ship. You put your payload on the ground ship where it ferried to a high altitude rendezvous with the orbital airship. The orbital airship raises the payload farther, to the highest point it can on buoyancy. That point is far below orbit, but the atmosphere there would be thin enough to permit the use of ion thrusters. Ion engines take the airship to orbit: a two week process. To return payloads from orbit the process is reversed.
Personally, I don't think this would ever prove to be practical, but it is possible to imagine it working.
The outfit behind this concept (JP Aerospace seems to be a volunteer organization of high altitude balloon enthusiasts. They've done a number of spectacular balloon missions, in one case sending a balloon to over 19 miles, or 1/3 of the way to the official "space" line. They don't seem to have done anything in the last year though.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
..a space escalator can never break, it can only become space stairs.
I am confident there will be no problems. Ship it.
Signed,
Bill "Shakey" Bradson
Lead Engineer, Tacoma Narrows project
Earth's gravity is substantially weaker at GSO. GSO altitude is large compared to the Earth's radius.
Space elevators *do* lower the energy that is supplied by the launch system.In a space elevator, the energy for the sideways motion comes from the rotation of the Earth (hence the Coriolis forces on the elevator mentioned in the summary). For GSO, that's less than the energy spent climbing up the gravity well, but it's still not trivial.
For escape trajectories, the elevator looks even more attractive -- once you pass GSO, the ride becomes free, and you gain energy from the dynamics of the system without spending any propellant / electricity / whatever. Time it carefully, and you just "fall" off the end of the cable on the right trajectory.
All of that said, rockets aren't *that* inefficient. For LEO, they can be 10% efficient or better (slightly worse for GSO). That's not great, but there are no proposed methods of getting energy to the elevator car that are all that efficient either, especially when you count electricity generation losses. Given the disparity in capital costs, and the fact that in neither case is the energy cost a noticeable fraction of the budget, I suspect rockets will win out for some time to come...
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 lower you step off, the less velocity you have, and eventually your orbit will intersect with the surface of the planet.
Ah yes, my arch nemesis: the surface of the planet. The same thing that keeps me from achieving free fall with every step I take. "Woohoo, I'm in orrrrr.. [thud]. DAMNIT!"
https://www.eff.org/https-everywhere
To use a car analogy, do you think that a fly sitting on your car's antenna will drastically alter your fuel consumption?
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
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
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.
I think the Ninja Turtle you meant was Leonardo ;)
Of course it's possible to accelerate payloads gradually, using a launch ring.
Another cool idea: airship to orbit. More. Still more.
In any case, we need something beyond standard chemical rockets to get cheap access to orbit.
Q: What does the "B." in Benoit B. Mandelbrot stand for? A: Benoit B. Mandelbrot