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Space Elevators Face Wobble Problem
NewScientist is reporting that while the strength of the tether has long been considered the main problem in building a space elevator, a new study suggests that a dangerous wobbling problem may also be a serious obstacle. "Previous studies have noted that gravitational tugs from the Moon and Sun, as well as pressure from gusts of solar wind, would shake the tether. That could potentially make it veer into space traffic, including satellites and bits of space debris. A collision could cut the tether and wreck the space elevator."
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Because escalators don't break... they just become stairs.
Well, back to rejecting software patent applications.
riding the rickety elevators at my alma mater!
You'll end up somewhere very improbable.
If you mod this up, your slashdot background will turn into a beautiful sunset!
Why would somebody want to prevent that? Free fall would be the most amazing part of the ride.
RutSum.com
Funny that. Another piece of science fiction engineering, Ringworld, is unstable too. Nevertheless, I still think the space elevator is a ponder-worthy pipe dream.
i\hbar\dot{\psi}=\hat{H}\psi
The space-time continuum has not been kind to you.
If you mod this up, your slashdot background will turn into a beautiful sunset!
During a speech he once gave, someone in the audience asked Arthur C. Clarke when the space elevator would become a reality.
"Clarke answered, 'Probably about 50 years after everybody quits laughing,'" related Pearson. "He's got a point. Once you stop dismissing something as unattainable, then you start working on its development. This is exciting!"
http://science.nasa.gov/headlines/y2000/ast07sep_1.htm
any who has ever seen cartoons as a kid would know this :p
The Mothership
Space Elevators are not simple to build!
I never saw that one coming!
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
I would be more concerned about the space elevator becoming a giant van degraff generator. Something that long would present some very interesting problems. Huge frikin lightning rod might be a better description.
"Trademarks are the heraldry of the new feudalism."
n/t
seemed to work fine for getting Charlie and Wonka into space. although it wasn't supposed to do that...
01110000 01010111 01101110 00110011 01100100
Make the elevator teether out of weebles.
Next.
I don't think anybody really thought building a space elevator would be as simple as reeling out some cable and strapping on a cabin. There are a million complications, even before we get to solar winds or tidal pulls. How about something as simple as airplane traffic? Birds? Squirrels, for goodness sake!?
Plus a million things we haven't thought of, and won't think of until the product is built. When train tracks were first laid down, they were too close together, because nobody had heard of the Bernoulli effect. Trains were getting slammed against each-other by their own created air pressure. What did people do? They learned from it, and moved the tracks further apart. We take trains for granted, but they were not without their technological hurdles to overcome.
Of course something like a space elevator is not an easy accomplishment. Does that mean we shouldn't try?
What do you think?
My guitar chord generator.
You really mean to tell me this batshit crazy idea that requires massive advances in materials science even to become technically feasible might just possibly not be entirely practical?? Say it ain't so.
I lost 50 pounds due to the wobble!
Thanks space elevator!
"Quote me as saying I was mis-quoted." -Groucho Marx
IANASEE (...Space Elevator Engineer). But it would seem that the solution to this particular issue would be multiple end-points in space. It would dampen the wobble, and also provide a degree of redundancy...
"Be light, stinging, insolent and melancholy"
Basically, the problem has been noted before this Perek guy's paper, but not studied in any detail. Perek reiterates and perhaps expands upon the concern, but doesn't do any analysis to establish the actual likelihood of a problem. It's basically an opinion.
Atmospheric oscillations should be extremely well damped by drag. Oscillations due to gravity from the sun and moon may be a greater concern, because there is no drag, although including conductive paths in the cable may allow the earth's magnetic field to suitably damp the oscillations.
An IEEE article on the topic discussed the related issue of harmonics. If these oscillations propogate through the cable at a rate that syncs up well with the rotation of the earth, gravity of either the moon or sun may amplify them. The tensile component can be tuned by adjusted the mass and tensile stiffness of the cable, and even better, the mass of the counterweight, allowing you to tune it by changing the tension, like an incredibly huge guitar string. The will also be a pendulum like motion due to the fact that the earth is on a tilted axis. This seems to be the concern discussed in the article.
I personally am not at all convinced that oscillation of the cable alone (waves) is a problem due to it's low density, but oscillation of the combined cable and counterweight (pendulum) may be. If so, thrusters on the counterweight are much simpler to attach and refuel than they would be at intermediate altitudes on the cable.
Looking at the sheer size of this, I'd say that 'wreck the elevator' is a major understatement. Look at all the other stuff that would be wrecked. I remember reading a Ben Bova book a while back where terrorists sabotaged an elevator. They went to the top and severed the connection to the counterweight. The rest of the thing toppled like a flimsy tree, wrapping itself 1/2 way around the earth. Yeah, scifi, but it could happen.
Do not meddle in the affairs of sysadmins, for they are subtle, and quick to anger.
getting stuck in an elevator in a NYC skyscraper, imagine a brownout halfway between here and the moon.
Yeah, something like that could ruin your day.
"Honey, yeah, I'm going to be home later than I thought. Don't wait up for me, little elevator problem"
Every time you call tech support, a little kitten dies.
Just absorb wobbles when they reach the ground station, by moving it.
The elevator string behaves like a one dimensional wave, and they can be completely absorbed at a point.
It could also be steered by that point, the ground station.
Kim0
A practical elevator is going to need a lot of armor to protect it from debris for a considerable portion of the low earth orbital space.
Couldn't we just hook up adjustable tuned mass dampers every few hundred meters? It works for cars and skyscrapers.
Looks like we just created a new job - cleaning up the crap and satallites orbiting in the right-of-way that the cable will require. Who's gonna hold the Hefty while I sweep this up?
I realize that the space elevator has a coolness factor, on a scale of 1-10, of about 14, but still, why is it all we ever hear about? There are other designs for low-cost orbital launch systems that would likely to be a lot more feasible in practice. Namely, http://en.wikipedia.org/wiki/Launch_loop, http://en.wikipedia.org/wiki/Space_fountain or http://en.wikipedia.org/wiki/Orbital_ring, altho the orbital ring variant would be a larger construction, but should pose fewer engineering issues.
Nobody expects the British Columbia Human Rights Tribunal.
Just make it out of Scrith, that should be strong enough to withstand debris impacts.
If you build it, nerds will come. Soylentnews.org
The old well worn bridge analogy: In theory it's pretty easy to built a bridge, but you need to only look at the Tacoma Narrows bridge to see that engineering a viable structure takes a bit more than str theory is prettSame deal with a space elevator. The theory is pretty straightforward, but the actual engineering to make a reliable structure is something else.
Engineering is the art of compromise.
What is less clear is how eneregy and momentum would be recovered on a payload descent. Perhaps balanced by an ascending load on pulleys.
is surely the biggest problem :)
The resonate frequency of the 'wobble' would be extremely low. Therefore, it would be possibly be imperceptible without the use of instrumentation. However, over time this resonance may build up over time, requiring an extremely small amount of thrust to correct. The (cycle) period would be in days and depending on design, harmonic and overtone activity would be lower than the fundamental by a considerable amount, at least six dB an octave. (Which would be very serious if only odd harmonics were produced.;) Clearly this has been simulated (and its quite easy) on a computer before?
Personally, while I respect the editorial staff of New Scientist greatly, people do make mistakes and since NS allows some types of advertising, a little bit of sensationalism can have its leeway. Somehow it might be tied to a very low tech product that is all over the pages of NS: The automobile.
Opinions on both sides, it seems. I guess we'll have to build one and see what happens.
"Yo, I was like going up in da space elevator with my hommies and E-lek-tronic Dawg when the whole thing started goin' all Wibbly Wobbly like. I pulled out my Sa-honic Screwdriv'ah an dun popped a sonic cap it the monofiliment resonator. After that is was all like that bitch Sarah Jane, smooth as her backside was 30 years ago when she was still hawt, ya' know what I mean G? "
Tsukasa: All I really want, is to be left alone...
I'm no rocket scientist, but the article cites a concern that this wobbling cause space elevators to become more expensive and difficult to build. OK, I'll give you that adding a thruster system will increase the cost of your project, as feature creep often does, but wouldn't the cost of doing so be vastly exceeded by the very rocket launches that this elevator intends to replace? Wouldn't the costs of added complexity and materials be vastly exceeded by the cost of repeated rocket launches?
This is like worrying now about what to wear on your 250th birthday. We won't see space elevators in my lifetime, in your lifetime, or in the lifetime of your grandchildren. We can't even come close to constructing even a tiny fraction of a percent of the material of the required strength for a space elevator. A bit of wobble is neither here nor there. And when we do have the technology to make such material in bulk, we'll have already figured out countless solutions to the problem of wobble and most humans will probably think of space elevators as a fun way to get *down* to the old planet their ancestors used to live on rather than as a cheap way to get stuff into space. Next up, the impact of proton decay on the stability of your home.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
It seems to me that, at this point, launch loops are a much more realistic and practical choice for a launch structure than space elevators.
Unlike space eleveators, launch loops require no exotic materials (just iron and steel), are essentially self-erecting, are anchored, and accelerate people quickly through the radiation belt.
We could probably build a launch loop in a decade or two, if we embarked on an Apollo-like program.
The Stealth Nighthawk fighter could not be controlled by a human, it is so aerodynamically unstable. But with the help of some good software, that plane flies. The same is true of the B-2 Batwing bomber, it only flies because a computer stabilizes it.
There will be controllable vanes (for the atmosphere) and thrusters (for space) to control the car's behavior. The wobble would be predictable and all the traffic would be required to avoid it, in the same way power boats are required to steer around sailboat.
Solar wind around Uranus, shaking and tugging your tether, both could cause dysfunction when getting your elevator up.
That's no longer considered a critical problem. First, everything that's in orbit and over 10 cm in size is already being tracked, and they're working on bringing that down to 1 cm. Therefore, if it's know what's on a collision course with the ribbon in advance, it's possible to simply move the ribbon out of the way in advance by moving the anchor at its base. One of the things that makes this approach feasible if the fact that most satellites and orbital debris is at 500-1700 km altitude -- a small fraction of the total length of the ribbon. Also, by doubling the width the ribbon between the above critical altitudes, it's possible to decrease the risk of a catastrophic failure due to an orbital object impact by another 30%.
Source: Edwards & Westling (2002).
Has nobody stopped to ponder the effects of rotation and orbit?
I wouldn't want to be in that tether's path when the moon disappears beneath the horizon.
They tried to do that once and failed, so they're skittish about the whole current carrying tether thing.
In order to make a power available from a space elevator you'd need superconductors. Even on a relatively short (12.5 mile) cable they got 3500 volts@amp.
Actually on second thought, I'm not sure they would get ANY current to flow. The reason current flows is because the conductor is traveling with respect to the magnetic field. That probably doesn't apply to a stationary space elevator. A skyhook, or a series of space elevators sure. Also, if instead of generating power you feed it power from solar panels, you can alter its orbit.
They ARE out to get you simply because They are in it for themselves and they don't care about you.
and spellbinding, death spiral to the ground if it stops going up. Gives a new meaning to "vertigo", since you will VERTICALLY GO down on this spin...
Previously: "Linux... Toward the Sunrise..." Now: "Linux... Toward the-- No, now, part of Every Sunrise"
I'm not saying that space elevators are going to cut it one day, but that current is usable for sure, if only to make the fucker glow, or to discourage the squirrels another poster was so worried about....
"Be light, stinging, insolent and melancholy"
"A microprocessor... is a terrible thing to waste." --
GeneralEmergency
The top of an intact space elevator in orbit would move eastwards, just like the ground under it does.
The top would move at a much greater speed than the ground, since it is further from the center of the earth and has to cover a greater distance for a full circle.
As any part of this elevator falls towards earth, it would keep its greater eastward speed and therefore overtake its anchor point quickly.
Just because it's unstable doesn't mean it's impossible to get working.
For instance most modern fighter aircraft are aerodynamically unstable, but they still fly. For example, the F16 was deliberatly designed to be unstable (to gain better manuverability). Of course the F16 has a computer control system to make it flyable by humans, but if the computer dies, well, unstable tumble modes ahead... I've also antecdodally heard that some modern bridges and tall-buildings are also not inherently stable (and are actively stabilized by computer control systems).
But to be honest, I think the engineering of a space elevator is pretty much beyond our forseeable technical ability (material science, control systems, assembly techniques, not to mention project management, risk/return estimation, and financing/underwriting).
If you think the problems are merely about waiting for technology, just think of the chunnel. It was imagined for a long time, but even after they got all the science and technology and assembly issues under control, the project management, risk/return estimation and financing/underwriting issues managed to kill a few companies before if finally got done.
They should try bracing the structure with these. As I understand it, they wobble but do not fall down.
Kwisatz Haderach
Sell the spice to CHOAM
This Mahdi took Shaddam's Throne
Euler think they would have thought about that. I've heard it's all the mode these days.
They've solved the elevator music problem?
Have gnu, will travel.
allowing you to tune it by changing the tension, like an incredibly huge guitar string
Great. So now instead of wobble we have to worry about hiss and distortion!
Not to mention that every dork who strolls by will be trying to pluck out a tune on it. The base station will need an incredibly huge "NO STAIRWAY TO HEAVEN" sign.
Soylent Green is peoplicious!
Well, maybe not. In fact, I didn't even RTFA. But never mind about that.
OK, so here's an idea. I haven't thought it through in even the slightest way, so it's bound to work.
Rather than have just a single tether straight up, have 3 or 4 arranged regularly. Let them connect at terminus. At the terminus, for no good reason at all, have spoke stations rotating vertically around the hub.
Would you like a slice of toast?
How is someone who shows a total lack of understanding of basic physics 'Insightful'? As the cable gets closer to the Earth it speeds up relative to the surface. It's called conservation of angular momentum. It will indeed wrap around half the planet, though much of it will probably burn up in the atmosphere on it's way down.
I'd imagine a solutions for this would be simple, just not obvious until it was built. The first few elevators would be developmental and go through a couple of generations before being considered 'operational'. Perhaps resolving problems like this may be as simple as having two counterweights at the end where one is the actual 'space station platform' and a second counterweight is reeled out to space and back in again in response to vibration and/or the earth end is completely submersed and adjusts it's buoyancy in response to vibrations.
I'd imagine these kind of things, including sensor points on the cable, would be necessary to facilitate alignment of power transmission to the cars traveling on the cable, even the cars traveling on the cable could be part of the dampening system by adjusting the rate of climb and having cars change direction to perform dampening maneuvers. Passengers would view it in the same way an aircraft lines itself up with a run way or is put into a holding pattern or it could be done with empty cars or freight cars on the same cable.
In other word's studies like these should be welcomed so that issues of this nature can be considered and addressed. Now has anyone considered whose systems would be appropriate enough for a computer simulation of a S.E to uncover any other issues we may have?
My ism, it's full of beliefs.
Just name it Weeble. Then it can wobble all it wants.
One of the oft-overlooked, less attainable aspects of a space elevator is... duh duh duh... the counterweight. Stated simply, it's a large mass way farther out than the 'top floor' of the elevator (or maybe be the top floor) otherwise all of the mass of the ribbon which is below circular orbit speed wants to fall. The counterweight wants to fall UP, thus balancing.
;-)
Generally, were talking either a LOT of mass a little ways further up, or a little mass WAY further up. Too much further and stability gets worse. Think of a longer radio tower.
Ok, so no problemo... capture an asteroid and move it into position... anchor the ribbon to it... No... err... problemo... WAIT A MINUTE!!!
That means scooping up and asteroid from less than HALF a Lunar Distance AND STOPPING IT in a very short time... or finding a more reasonable velocity differential and... dropping it into place. Yeah, Earth Dome will let us do that. We'll just drop it to 22000 kilometers... err. MILES!!! I meant miles!
But that is not the show stopper... it's this: Even over a long time, it will take a LOT of propellant and energy and mass to comply with Newton's "equal and opposite" clause. Given that the 365-foot Saturn V put a Volkwagen Beetle on the Moon, and that modern rocketery might be able to put a Ford Excursion on the Moon... now scale the VW up to the size of the asteroid in question... and the Saturn V by the same factor. HOLY NIKE SMOKES!
Let's say that a shuttle could carry up a mile of ribbon. That's 44,000 shuttle launches (22K + counterweight tether.) !!! So, tell me... what will this Space Elevator do that can't be done in the 44,000 shuttle launches NOT COUNTING the dilithium we'll spend getting the counterweight into place?
How many space tourists paying how much will it take to recoup that investment?
You build this giant ass ladder to get to the heavens, and then it comes crashing down spreading people all over the earth. "Honey, what was that loud thud I heard." "Oh, it was just a corpse landing in the backyard from the collapsing space elevator." I bet those guys that built the Tower of Babel never played Jenga.
Never monkey with another monkey's monkey.
For those interested, This new study -or any study at all involving the effects of gravitational tugs on the cable, is not going to release the REAL REASON WHY this influence exists. This is due to a massive coverup on the existence of a rogue planet in the Solar system since 2003. Either the people in the study don't know of the Planet, or they do and are "told" not to divulge the Truth of it. Why cover it up? Because it's gonna break things, big things; think POLESHIFT; not only that, be aware that many will die as a result, and many have in the past, as it is an orbiting planet: One that passes through the ecliptic every 3,656 years. (If anyone would like historical references on this, I can provide sources) In my studies on this subject, I think the Poleshift will happen within a year or two. When it does, we're talking new continents (remember the stories of MU and Atlantis?) reshaped current ones, new axis tilt (90 degrees as opposed to the current 23.5), massive worldwide tsunami's (makes the 2004 Sumatra Tsunami look like a good surfing wave) and Richter 15 earthquakes. Would YOU like to be the government elected official to to announce this one? Even most spiritual channelers don't want to admit it.
I was really unhappy when they survived. I'm not a mean person, by Phyllis seemed to be really evil. I really wanted to hear about them getting ejected into the outer solar system by Jupiter.
One must not confuse the improbable and seemingly unnatural with the absolutely impossible.
(Man darf nicht das, was uns unwahrscheinlich und unnatürlich erscheint, mit dem verwechseln, was absolut unmöglich ist.)
- Carl Friedrich Gauss
As someone who once owned a ZX81 with the 16K Ram expansion pack can attest, yes, it can be a real pita
If a harmonic of the cable got involved it could be a rough ride.
Less than 9,000 km of land out of 41,000 km of equator.
The WTC towers were precisely dynamited, if you care to watch the Zeitgeist movie [ www.zeitgeistmovie.com ].
Because escalators don't break... they just become stairs.
"Sorry for the convenience."
Cool! Amazing Toys.
Engineering a viable flying car is far beyond making one unit that can fly, it also involves establishing safe flying practices etc: in other words, full system thinking.
Engineering is the art of compromise.
The reason I thought no current would flow for a traditional space elevator is for the same reason an electric motor does not generate electricity if it isn't moving. The linked article is talking about a mission flown from a moving spacecraft, not a stationary (with respect to the earth) object.
Yes, the materials had an easily solved problem, however compared to a space elevator (24,000+ miles) the length of the tether they used was positively tiny (12.5 miles). If I'm wrong about the magnetic field and it does generate electricity, you'd need to put up a microwave generating station every 20 or so miles to keep the cable weight down. Hmmm, I wonder if a superconductor in the shade of the cable and open to space would cool down enough to superconduct.
They ARE out to get you simply because They are in it for themselves and they don't care about you.