Slashdot Mirror
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.
How about a space "cannon" like in Final Fantasy 8 then?
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.
realists when I say:
DUH!!!
Thank you
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!"
In addition to coreolis effects and solar wind, simple atmospheric turbulence would pose significant problems with such a massive structure.
Examine the problems associated with the construction of skyscrapers. A cable ascending out of our atmosphere would have tremendous torsion stress.
Not to mention the absurd logistical costs involved in trying to get the cable taught in the first place. Before the orbital tether is entered into geosynchronous orbit, it would be subject to gravitational compressive forces as well. Attempting to unspool form orbit would energize the holy shit out of the cable, as it was drug through the atmosphere.
An orbital elevator is a novel idea, but it is best left in the realm of science fiction.
Place the elevator on the North Pole.
If that doesn't work, we can always use the South Pole.
...,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.
Great. That heading was supposed to have been "Fixed thrusters > rockets". Hm.
A good place to start is to read the book
They All Told the Truth: The Antigravity Papers
by Richard P. Crandall
http://www.amazon.com/They-All-Told-Truth-Antigravity/dp/1553957237
Notice that the typesetting on this book is very bad, so if that is all you look at you will be very disappointed.
But this book will teach you how to build a anti-gravity generator and will provide you with
the theoretical foundation for understanding anti gravity.
But to understand the theory you should know about
general relativity and quaternionic electromagnetism.
http://www.scribd.com/doc/4445/quaternionic-electrodynamics
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."
All they have to do is redesign the car/platform/etc a little bit to compensate.
And a small rocket would be a very small rocket, actually. we're talking hardly any more powerful than a few model rocket engines to counteract these forces.(think small thrusters or a tiny jet engine)
It's doable. Just not as easily as we once thought.
By the farking article.
There may be some real stuff behind this, but it sure doesn't read like it. You might go into orbit, 40,000 km from the Earth, off by a few dozen km ! And that might take fuel to fix !
I would guess that whoever wrote that doesn't know much about geostationary satellite station keeping. And, of course, if you have an elevator, fuel will be cheap to lift too.
It is clear that a space elevator arm will be a dynamic structure. And the schedulers of traffic will have to take the conservation of angular momentum (the way to look at the Coriolis force in a non-rotating reference frame) into account. But just because the arm moves around doesn't mean it can't function.
Ion drives need physical fuel as well as power...
So, you'd still have to haul up fuel, just not as much as with chemical rockets.
MadCow.
Yeah, I know.
My point was more that, unlike with rockets, you could deliver the fuel in steady stream (elevated by solar-driven pumps, near-asphyxiated climbing space donkeys, or whatever). Which I suppose, in the long run, *has* to be better than strapping a rocket to a rocket to bring the fuel for the rocket for the fuel for the rocket! ;-)
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!
My understanding is that Ion drives also need a ton of time, as their acceleration is like a giant curve. It would not be suitable for countering things in anywhere near real time.
IE, a probe might take a month to get to the moon, but only 2 months to get to mars, etc.. (I know, my numbers are way, way off)
What are we going to do tonight Brain?
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
... if you apply horizontal thrust as you move upwards, you can exactly compensate for the coriolis force. Since you know the vehicle weight, and the distance you move upwards, you know exactly how much thrust to apply.
I, myself, subscribe to Gene Ray's view of the world. Works for me.
Faster! Faster! Faster would be better!
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.
"The coriolis effect is not a real force."
You are correct only in a narrow technical sense that you clearly do not actually understand. The difference between that and being wrong is a bit philosophical for me.
The coriolis effect is not a "force" in the clasical Newtonian definition. The coriolis effect is a real effect, that will cause real problems for anyone trying to build a real space elevator.
Just go up from the pole, instead from the equator?
Ion drives are limited by a combination of available power and specific impulse (thrust to propellant mass efficiency, if you will). If you want very efficient thrust and have extremely limited resource for power, you're stuck with the current very small accelerations. However, it is possible that these thrusters may have access to enough power to do credible real time adjustments and still maintain the specific impulse/high efficiency. Or the thrusters may go with somewhat lower (but still much better than chemical rockets) specific impulse.
Honestly, why use climbers? Do we use climbers to go up and down regular elevators? No, because that would be stupid. We have cables attached to the tops of cars, and a counterweight. We should do the same thing with the space elevator. That has the added advantage of keeping all of the moving parts up on the space station (or on the ground, depending on your design), which prevents breakdowns in areas inaccessible repair crews.
Hell, you could probably get away with simply having a big rock somewhere past geostationary orbit tethered to a (very heavy) base station, and simply roll the whole array in and out, with the payload fixed to the ribbon. It would be kept straight by the centripetal force, despite any other forces acting on it. If you HAD to keep it PERFECTLY straight all the time, you could put boosters on the counterweight, but that hardly seems necessary.
matter.
Obviously, Slashdot doesn't want to tell its readers that
there are NO IT jobs.
I hope this helps.
Thanks for nothing.
PatRIOTically,
Kilgore Trout
What about a stairway to heaven? It seems to me there are two paths we can go by; in the long run, there's still time to change the road you're on.
No. You're thinking about the distance vs. time curve.
That's because ion drives create a very small force, which gives only a very small acceleration.
But Coriolis force itself is not large, so ion drives might have just enough thrust.
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.
surely, the development of any space elevator would have more than its fair share of,...er..., ups and downs... (sorry)
Technically you'd have to haul up the propellant, where as the "fuel" would be the electric power used to accelerate the propellant. Posting as AC for being overly picky.
Just ask a rock band to solve the problem.
Excuse me, but please get off my Pennisetum Clandestinum, eh!
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.
Am I the only one who thinks that a space elevator based on a tethered weight in space(if it actually worked) would drastically alter the Earth's rotation?
You're right about the Coriolis force being illusionary. What they really mean is that we'll need some additional force on the elevator to give it its spiral trajectory as the earth spins.
The space elevator is like fusion power only 100 years in the future. The difference between the space elevator and fusion power though is that we have actually achieved fusion just not useful fusion we have never done anything even close to making a space elevator (although I believe we have played out lines from the space shuttle).
Personally I think if a space elevator is physically possible it's so far away into the future as to be fairly meaningless to us. The technological hurdles we need to get over before we can even think about trying are huge. In fact I imagine we would need to overcome other hudles in politics and economics before we could even make an attempt. For example the first elevator would have to be a world project - how would we get that many nations working together for a long time and not pulling out? How would we finance it? I don't think our current economic principals allow us to work on projects of this magnitude.
I used to have a better sig but it broke.
By the time our technology is advanced enough to build a space elevator "the right way", we'll be able to get stuff into space through cheaper, more simple, more reliable means. The idea is interesting in a 1940's flying-car kind of way, but not in a 2240's star-trek kind of way.
The driving desire behind a space elevator is to reduce the amount of energy required to lift an object up to a point where the Earth's gravity is sufficiently weak to use 'lower power' rockets for establishing orbit, or leaving the Earth entirely. When considering the energy requirement, you can break the energy into two components - the energy of motion of the mass (kinetic energy), and the gravitational potential energy. The gravitational potential energy, if you haven't taken physics or don't remember, is the fact that in order to lift any object to a given distance above the Earth's surface requires an investment in energy. I don't know what the formula is for lifting an object that far above the Earth's surface, but we don't have to know it for this discussion. Whatever that formula is, that is the 'minimum' energy needed to get an object to a certain elevation.
A rocket or a space cannon would both essentially do the same thing - accellerate you to escape velocity (or sufficiently near it to reach the desired elevation), 11.2km/s. But, the formula for the kinetic energy of an object at 'low' speeds (and escape velocity is low compared to the speed of light) is k = .5mv^2. Where m is in kilograms, v is velocity in meters/sec, and k is energy in Joules. Because 11200^2 is a very large number ( 125440000 ), even when you halve it, it's still a large number (62720000). Which means it takes a whole lot of energy to lift anything into orbit by accellerating to, or near, escape velocity. Consider an object which, at the Earth's surface, weighs 1000 lbs (so it has a mass of 453.6 kg). To accellerate to escape velocity, that's about 28.45 GigaJoules of energy required.
The only advantage the space cannon would have is that instead of having to use a lot of fuel to propel it, you could use an array of fission or fusion reactors to supply the energy required. But it's still a lot of energy. It would be better to reduce the amount of energy needed.
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 --]
But is the space elevator dead? No.
The space elevator is "not dead" in the same way that my unconceived and unborn children are "not dead."
I'm not saying that a space elevator is impossible. (Nor is it impossible for me to have kids some day.) But saying the space elevator isn't dead seems like a poor description.
Is there *any* way to move/accelerate in space given unlimited quantities of energy (and short of converting energy to matter) ?
Why OpalCalc is the best Windows calc
But the real question is what kind of space elevator music will they play? I'm not sure if I can handle a day and a half straight of "Girl from Ipanema".
"But this one goes to 11!"
A small wobble in the belt makes the Right Time hard to guess.
- "History shows again and again how nature points out the folly of men" -- Blue Oyster Cult, 'Godzilla'
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.
If you translate mass and force into electrical terms, ion drives have extremely high voltage and almost no amperage to speak of. This makes them poor for certain kinds of applications. But, the fact that they have no amperage (they move very little mass) also significantly reduces their reaction mass requirements. They are also electrically powered, and that means they can be 'fueled' from the ground by shipping up relatively massless electrons.
One interesting thing is that in the atmosphere their reaction mass is free. That only covers (I believe) the first 50-60 miles of the cable, but it is something.
Lastly, having the thruster affixed to the cable is an option, but so is having it affixed to the load being hauled up. That means the reaction mass can be in the load and with an ion thruster I'm guessing you could haul up several tons of load with only a few hundred pounds of reaction mass, which is still a huge improvement over a standard rocket which needs 10s or hundreds of pounds of reaction mass for every pound of load.
Need a Python, C++, Unix, Linux develop
Actually, launching stuff beyond earth orbit is one of the intended applications. Not the only one, mind you, and maybe not even the most important, but it's not a new idea. In order to function properly (i.e. not fall down), the elevator will have a counterweight on a tether beyond geosynchronous orbit to counteract the weight of the tether between earth and geosynchronous orbit. If you go out to the end of the tether where the counterweight is and let go, you get flung off into space with considerable velocity. Depending on how long the counterweight tether is, you could lob stuff off the end and have it arrive in the vicinity of, say, Mars, without having to use rocket propulsion at all.
The article seems to be saying that you aren't going to be able to lob stuff off the end with any accuracy if it's swinging back and forth. I don't see this as an unsolvable problem, just a matter of keeping track of position and velocity of all parts of the elevator at all times and being able to make accurate simulations of the results of any actions before they're taken.
Also, the elevator's rotation is going to be inclined to the plane of the ecliptic anyways due to earth's tilt (unless it swings back and forth to compensate), so proper alignment wrt mars (or other exciting destinations) is already going to depend on time of day and time of year (to say nothing of the position of mars).
ITYM: http://en.wikipedia.org/wiki/Launch_loop
Huh? Where have you been the last twenty odd years? Space Elevator proponents have been explaining how easy (conceptually and practically) an elevator will be for a couple of decades now, though the more intelligent among them have always grudgingly admitted that materials would be the key bottleneck. But the discovery of carbon nanotubes converted most of them to the see-no-problem fanboi side of the fence.
Yeah, actually I do. (Somewhere around a dozen.) But you are comparing apples and oranges - because while a lunar landing can be prepared for incrementally, you can't build a space elevator in the same fashion. One up, all the way to completion - because an incomplete elevator not only is useless, but unstable.
If you don't haul mass up, your ion drives aren't doing any driving. They need fuel too, not just power.
We figured that out in about 10 minutes 25 years ago. I used it a test case for my trainees at work. To make it function, it requires an active stability control system.
I doubt that this is news - I find it unfathomable that the people who have researched this actively over the year are unaware of this. If they are they are even less competent than I thought.
Brett
Coriolis is indeed an effect of the rotating reference frame, but the dynamics *do* require something to be done about it, because the reference frame (i.e. the Earth) is in fact rotating.
Brett
from the get-go see this was the veritable (and now, verifiable) "spiral of doom", leading to a winding, windy death for any riders? I guess the bonuses are spiraling and winding around an axis of death. Not a bad, uplifting way to "check out" of this realm of existence...
Previously: "Linux... Toward the Sunrise..." Now: "Linux... Toward the-- No, now, part of Every Sunrise"
This would address two problems:
The more I think about it (haven't thought much ;-), the more I like it!
Strictly speaking - Photon Rocket. You can make one with just energy and a light bulb. But, you are dealing with a propulsion system that has all the thrust of a flashlight. In general, you will need to be very, very patient with such a device. If you have the engineering resources to put up nuclear fuel for your atomic reactor or whatever, then you can probably just as well use rocket fuel instead. AFAIK, nobody has ever built one and used it in space.
The problem seems to be if the elevator is actually firmly tethered to earth. Simply let it float at the base and the oscillation period should be long enough to easily catch it and load a lifter. Why complicate it by attempting to anchor it?
The fuel consuming thrusters wouldn't necessarily negate the benefits of the elevator. I've never assumed that the station for the space elevator wouldn't require thrusters. I have made the assumption that thruster fuel (or reaction mass and raw electricity for some kind of ion engine) would need to be constantly shipped up the tether to the station along with other supplies. So no big shock here. I don't think anyone ever claimed that a space elevator wouldn't be a complex engineering project, or that it would take loads up for free, there's just the hope that it can be done without using something like 40 times the mass of the payload in fuel and disposable tanks to get it up there.
Of course projects like space elevators and launch loops (which may be a lot more in the realm of possibility than space elevators) are massive scale projects that have big up front costs, probably dwarfing the costs of the existing rocket based space industry. With those technologies in place, the cost of getting payloads to space may be greatly reduced provided that they're used at close to their capacity. The problem is that the current demand for such services may not even come close to the capacity of the elevator/launch loop/etc. so it may end up being more expensive than rockets. If the price to get to space is greatly reduced, however, we might have a space boom and end up sending a lot more things into space. The problem with that is that payloads going to space typically need lots of engineering and design times are measured in years and the engineering that needs to be done may be heavily reliant on knowledge of the launch vehicle... In other words, there are a number of big chicken and egg problems. Basically, you may not be able to build an advanced space delivery platform like the space elevator or a launch loop unless you already have commitments from businesses to use it (possibly without commitments from businesses that could only actually exist if that delivery platform were a sure thing) who would be developing their payloads while the delivery platform was being developed and built. Otherwise, the supply/demand curve might not have enough time to ramp up during the useful lifetime of the elevator.
So, the space elevator, or any other hugely expensive next generation space delivery platform, would need someone with very deep pockets and some very strong central planning to come to fruition. So probably only a large government that isn't broke and in massive debt could tackle the project. In other words, we're not likely to see anything like that soon.
Sadly, about the only economic/political situation I can see where something like this might get built is if a killer app turns up. Something that requires huge volumes of material to be moved off the planet. About the only chance of that is if some calamity is discovered with a very long lead time, like say a killer asteroid that will hit earth in a decade. Then every major government on earth will be clamoring to pass "Colonize mars and get as many humans off the planet as quickly as possible (political leaders (and teenage mistresses) first) also, please see attached rider removing term limits and delaying frivolous elections until the current crisis is resolved" bills left and right. Not that I'm cynical.
Just thinking, if there was metal wire that was interlaced with the CNT cables, and the lines did wobble due to the Coriolis effect, The magnetic field generated from moving in the earth's magnetic field would act as a brake and minimize movement. i remember that this type of technique is used in minimizing motion when using ATM's and nano-positioning devices.
Yes - turn the energy into photons, and point them out the back. The photons impart a tiny bit a momentum when they fly away.
Sort of like a solar sail, without the solar.
while (sig==sig) sig=!sig;
Look up the Bussard Ramjet. It uses free-floating interstellar hydrogen gas as its reaction mass.
..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
Sure. Given unlimited quantities of energy, you can get something very, very, very hot. Direct the photons boiling off of this hot thing to all go in the same direction. You end up going in the opposite direction.
Photons have no rest mass, but they do have momentum, proportional to their energy/frequency.
has its problems to overcome.
Coder's Stone: The programming language quick ref for iPad
Even if the geo-synchronous orbit of the station is around the equator, I see no reason to anchor the space elevator at the equator. Also, with the possibility of a constant supply of thruster fuel from the ground and also the tether to tug on, I think you get a bit more play than a standard geo-synchronous orbit. For that matter, why is the assumption always that there will be one space elevator tethered from the equator to a geo-synchronous station. Why not have three tethers, thousands of miles apart for stability? More? Any reason why not
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
TFA mentions problems caused by the effect of earth's rotation on the payload going up an elevator
built on the equator.
Um, hello? An elevator on the equator maximizes such undesired effects. If you're building an elevator,
build it on one of the poles. no earth-rotation acceleration issue.
Of course, that means your velocity is also zero, so you need that much more fuel to accelerate into a stable
orbit... but I'll leave it to a math geek to figure the numbers on which is more efficient.
"unknown but negative" strikes me as a wonderfully pessimistic phrase. So we don't know what the impact of using multiple loads would be, but it would be bad.
Sounds like someone's got a case of the Mondays.
But we seem to be able to find the courage to spend $34 billion on that.
Come 'on, cough up the cash for the Space Elevator! The only thing we have to fear, is a nerve-tingling elevator ride into outer space!
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
The regular Coriolis force builds as things move north or south from the equator. In this case it is when objects move up at the equator.
"researchers working on development of a space elevator (an idea we have discussed numerous times) have determined that the concept is not stable."
Not entirely stable... Chewie, take the professor in the back and hook him up to the hyperdrive!
Bow-ties are cool.
Coriolis force is zero at any point in the equatorial plane, which is exactly where all serious designs for space elevators put it, for exactly this reason. And oscillations are useful for all sorts of reasons, including object avoidance or placing objects in different orbits. Indeed, standard designs for space elevators are so stable, many people do not think they need to be anchored to the Earth at all, the end just sort of floats mid-air a couple of meters above the ground.
Now, the parent does point out that there is a small amount of drag cause by object ascending which are imparted angular momentum as they climb. This is why most serious designs have equal number of cars of about equal mass going up and down at the same time. The cars going down give their angular momentum to the cars going up.
Minor station keeping is still required, but it isn't much, relative to fuel costs to launch the normal way.
On a related note, read Red Mars for an excellent, although fictional, description of how a real space elevator might be designed and operated. It probably has its own design flaws nevertheless, but addresses all these issues in a realistic way.
I can't see such an arrangement actually imparting enough force on the Earth as to slow the rotational rate much at all. The effects of the moon's gravity on oceans (thus causing tides) would be many orders of magnitude greater.
Maybe it would be of concern over billions of years, but the Sun itself won't last that long.
Sure, let's build an elevator into space with something I could slice through with a chainsaw in a couple of minutes, A.K.A. a carbon fiber cable... I won't be riding the thing until scrith has been invented.
All this means is that it will cost more money to build. You can get around the problems by using a more massive anchor at the top and building it taller. "Instable" maens you have a design where pertabations cause a kind of feedback. So what you do is build it with a certain amond of side load built in.
Ok so many this raises the cost by 4X. I don't know
Why build elevator,stairs or similar staff thats prone to malfunction.Build a teleporter and here we go to space! Yea yea i know this isnt Star Trek,but dont u wish it to be from time to time? But most of all i would like it to be Star Wars,so i can be a Jedi :) oh fantasies,always funny.
Well, just dictate a pound of weight to every time the elevator goes up.
The Kruger Dunning explains most post on
Just put two climbers on there and flip one over to counter the twist of the other!
Simple as pie!
Sheesh, they should give me a job.
Instead of having something climb a cable, couldn't the space station just drop the cable down to ground level?
I may be way behind on the whole thing but does this mean we have worked out a cable strong enough for the project?
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 space elevator needs to be firmly set onto the ground, be at least 20 km in diameter and 40 km high. Lots of rental space included.
the monkey Arthur C. Clarke first proposed the space elevator in a science fiction book.
So did he with geostationary satellites.
He may not be right about space elevators but chances are..
gtkaml.org
I could use a lift.
This would pull the elevator away from its vertical resting position, causing it to oscillate back and forth like a pendulum
Haven't we solved this problem before? Many skyscrapers have a tuned mass damper at the top to stop vibration from wind and earthquakes. The scale is different, as is the cause of the oscillation, but the engineering problem seems to be the same.
Moderating "-1, Disagree" is simple censorship. Have the guts to post your opinion.
Make the counterweight a gyroscope.
Those babies will defy logical physics on earth, so why not in space?
Best of all they can be solar powered - and once they're up to speed probably wont require that much energy input.
If we bowed to those who say 'it's impossible' we would still be living in caves. I don't think it's ignorant to imagine what it would be like to have a space elevator and that we should build one, but it is ignorant to say that the problems are insurmountable.
I read the NIAC proposal by Edwards and, from memory, oscillations on a tether some 100,000Kms long were already a consideration, as was space debris, as was conductivity, as was atomic oxygen - these are some of the challenges - as is developing long strands of CNT's in the first place.
Ok, the trip will take a week or two, how long did a rail trip take across the us when rail was first established, or a plane flight from one side of the world to the other. Building a Space Elevator is going to be a very difficult thing to achieve. It's not anything we didn't already know, so keep on uncovering the engineering challenges and eventually none will remain. Then we can move on to solving them.
My ism, it's full of beliefs.
Will having three cables like a tripod instead of one help avoid the wobble problem?
A giant electromagnetic gun? Couldn't you speed a craft up to orbital velocity on an electromagnetic rail and just shoot it out of a really long barrel? I've always favored that approach. It seems more realistic than a space elevator built of nanotubes out of an asteroid.
I hold very few opinions. I hold information based on observation and fact. If you wish to disagree, please use facts.
I think any atmosphere thick enough to provide enough buoyancy is going to cause a horrendous amount of drag at those speeds. Low earth orbit is about 8km per second. Wind resistance goes up proportional to (iirc) the cube of velocity.
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
One thing that seems to have been missed in this discussion:
For much cargo, shipping in a matter of weeks at relatively low cost is perfectly acceptable.
Having a slow, space elevator as one of the shipping options would change the picture-and make some options practical that aren't practical now. We don't ship building materials by overnight air on the surface of the earth. In a practical sense, it can take days or weeks for building materials to get from their manufacturer to their ultimate destination.
Just having any lower cost options to get stuff to orbit is a huge step forward. Also, it is likely the first space elevator won't even be to the surface of the earth, but to the moon, because the engineering problems are less(basically using the moon as a quarry to facilitate orbital development).
A space elevator changes the source of energy that can be used for orbital transport. A rocket needs fuel. A space elevator can use power from a terrestrial power plant-or from an orbiting solar array( a solar array that can be expanded by using the space elevator itself!).
This is not for eart, we have wind huricanes, lightning, even airplanes, biological degradation, and also UV radiation and the van allen band
Also the seize required of this lift makes it a bit unrealistic to create on earth.
However just as a reminder the gravity on the moon is about 16.3% of earth's gravity.
There is no wind there, no lightning, no biological degradation,so it might work there.
Still you have to deel the hard radiation (which tends to break down complex molecules...)
So it might be better to have on on the moon, for a first practice
The problem only is then it'll cost lots of energy to get something like it there.
A better aprouch there would be an elctromagnetic railgun, and those might be used on earth too.
Perhaps dough a good jump would there would also be enough
I know you're out there. I can feel you now. I know that you're afraid. You're afraid of us. You're afraid of change.
I wonder if putting the payload into a rotation around the shaft of the elevator would help with stabalization, or two rings running opposing directions. I also wonder how the base would be attached, after enough length of elevator shaft, you may end up with centrifical force pulling the entire thing off the earth. Another thought, by putting it on one side of the earth, would it alter the axis of the earth or would oceans end up balacing it out?
The more I think about the space elevator, the more I think it's a bad idea and only workable in sci fi novels.
Consider yourself blessed if you are sneezed on by a dragon and only get wet, it could have been a fireball.
It's gotten significant attention by enough peer reviewed journals that include a lot of people who have education in physics.
The usual conclusions are that it's a tough engineering problem.
The NS article is sparse on what assumptions they made, but the illustration shows the carrier as being large compared to the tether. What I've read is the other way around. The tether is massive compared to the weight of the carriers.
The NS article goes on to say that they may have to move slowly. I don't see how this helps. As postulated the tether has no real damping mechanism. If I go up slowly or fast force times time will be the same product for the trip.
The key is going to be the ratio of the tension to the mass of the cable. Suppose that the tether has a natural resonate period of 2 days. Traveling up it in 2 days will 'pluck' it with maximal force. The tether will continue to vibrate for a long time.
Now send a second carrier up 1 day out of phase. To first approximation, it will cancel out the vibration induced by the first carrier.
Consider the situation when there is a carrier every kilometer both ways on the tether. At this point the coriolis forces are balanced. (Or not quite: They are balanced when the carriers are passing each other.
There are going to be higher frequencies on the line. Doubtless it will take some very clever engineering. But it's an engineer problem, not a physics problem.
Do remember Clarke's first law: When an (elderly) scientist says something is impossible, he is almost certainly wrong.
Third Career: Tree Farmer Second Career: Computer Geek First Career: Teacher, Outdoor Instructor, Photographer.
Geosync orbits were first thought up by Herman PotoÄnik in 1928 - a Slovene rocket engineer. It was proposed in Das Problem der Befahrung des Weltraums - der Raketen-Motor (The Problem of Space Travel - The Rocket Motor) where he also conceived the idea of a space station.
The problem with the space elevator is drift; just picture kids playing crack the whip while skating.
A much more ambitious, but stable plan would be to build a "wheel" around the planet, and anchor it at several (at *least* four) locations to the equator.
This way the wheel would provide most of the stability. You'd still need some propulsion contrary to the direction of planetary orbit, to keep the thing from wanting to "bulge" the other way, but a simple solar sail array at each spoke would easily take care of that energy requirement.
The rim would then become one huge space station.
Our current International Space Station, in low Earth orbit, is only around 200 miles up. With elevator cars moving at 250 miles per hour, that's less than a one hour trip. Folks could actually commute to orbit or vice versa.
Of course, a trip around the rim would take a little longer - at the same 250 MPH, around 4 days.
We could also use higher speed "rails" on the rim to help ships begin their outbound journey, using the inertia of the planet to give them a big boost. If we were *really* tricky, we could employ the reverse to help them dock, similar to the way fighters land on aircraft carriers.
It's really all about energy conservation, in the chic current, and Newtonian classic, sense.
One issue that hasn't been discussed is, whenever this thing *does* get built - and it should, from an energy perspective it's just the most sensible - how are we going to protect it from other debris currently in orbit? Huge "cowcatchers" surrounding the stalk, in the form of gargantuan beach balls? Armies of 'bots who swarm out and redirect the trash? Big flexible octopus arms that swoop out and deflect the debris? Onboard staff with high-powered laser rifles?
If your are maneuvering in a know magnetic field, you can react against it.
There is the solar wind that you can capture or react against.
Another idea. Instead of using solar cells to collect electricity to drive an ion engine, wouldn't it be more efficient to use a solar concentrator to heat a propellant directly to drive a reaction?
Aah, change is good. -- Rafiki
Yeah, but it ain't easy. -- Simba
Thats the biggest issue I see with beginning scientists and engineers. They are select problems to work that are too large and they wont make any significant progress. Or they select something trivial that may have been done already.
Doubtless it will take some very clever engineering. But it's an engineer problem, not a physics problem.
No. Engineering is the application of Physics and Chemistry. It would only be an engineering problem if all of the materials existed. Since no material designed or built exists right now or even in the near future that neets the requirements needed for the tether, then it is a physics problem.
Tesla was a genius. Edison however was a overrated hack who liked to torture puppies.
The biggest benefit of the space fountain is the cost savings, which can be had when a company president discovers that he can purchase pellets that are 1/4 the mass for 1/8 the price. He carefully makes the purchase 4 yrs ahead of time. Then, based on the savings that he has generated for the company, he assigns himself a higher bonus...
Then, inspired by the thriftiness of their president, the accountants carefully cut the (now doubled) pellet order back to the usual quantity, before going on a well deserved vacation to bora bora.
Backlogged by a truckers' strike,...
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
The space elevator *does* reduce energy consumption over rockets, because rockets have to carry their source of thrust up to the level at which it is burned, causing an exponential growth in energy consumed.
The elevator eliminates the exponential growth in cost. The gravitational cost of lifting electricity is minimal.
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
Sheesh!
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
Nice article, but no math to support it. Maybe by field testing similar scenarios the author could measure the actual harmonic that will occur? One of the things the article did NOT mention was the Static Electricity that will be generated when this baby goes 'up'. Talk about a Replenishing Energy Supply, there IS some solid evidence to support that statement. Which makes me wonder, "is there some kind of 'Thruster' the container could use in which Static Electricity is the fuel?" Maybe an electric Fan?
Of course there'll be vibration in a Space Elevator cable. You can't have a long taught cable like that without it trying to behave like a guitar string.
That's why you need magnetic dampeners on either ends. As soon as an oscillation starts to build, the de-oscillation computer program instructs the rings holding the cable in place to magnetically shift in the direction of the oscillation, thus causing the cable's movement to dampen.
Ummm...
You're thinking of Leonardo, not Michelangelo... ...you know, the one with the two swords and the blue bandanna?