Nope - the elevator has to be at the equator, and every satellite orbit has to cross the equator. As to how often that would occur - I'm not sure. I might be able to tweak one of my models to get an estimate though. I'll think about it.
Nope - the elevator has to be at the equator, and every satellite orbit has to cross the equator. As to how often that would occur - I'm not sure. I might be able to tweak one of my models to get an estimate though. I'll think about it.
There are meteorites of size varying between a tip of an needle up to the size of several kilograms. Now, while a needle travelling at several km per second would not be such a great danger for a cable of significant thickness, a rock 50 pounds (or let's say the nuclear reactor of an old satellite) is completely another thing.
How speedy of orbital debris could be? Let's say in low earth orbit, twice the orbital velocity (or 15 km/s). However, there could be debris that is attracted by Earth, and this could go much faster.
Now, most of the active satellites have small engines and those could be used to change the orbit. However, there are old satellites and other man-made debris flying up there.
Considering the huge amount of space, the probability for orbital debris/satellites to come within a certain distance from the cable is small. However, an impact could mean the end of the transport on the cable (using multiple cables would help).
How speedy of orbital debris could be? Let's say in low earth orbit, twice the orbital velocity (or 15 km/s). However, there could be debris that is attracted by Earth, and this could go much faster.
Now, most of the active satellites have small engines and those could be used to change the orbit. However, there are old satellites and other man-made debris flying up there.
Considering the huge amount of space, the probability for orbital debris/satellites to come within a certain distance from the cable is small. However, an impact could mean the end of the transport on the cable (using multiple cables would help).
That would be the max impact velocity for a satellite vs. satellite collision. But a satellite vs. elevator collision would be a max of about 8 Km/s in LEO (7.5 Km/s for the satellite, 0.5 km/s for the tether). Still, nothing to sneeze at.
Yep - highly elliptical stuff at perigee could be going a good bit faster.
Most of the stuff up there is debris, rocket bodies and dead satellites. Even within the active satellites few have any significant manuever capability, and that's only for as long as their fuel holds out.
It's not as big as you think. And you have to consider the lifetime of the elevator.
I wonder if even carbon nanotubes are strong enough for this. The pressure would be extremely immense. I'm trying to imagine it and the pressure which will be expressed in lbs per square inch. The lbs will be huge since it also depends on the length of the elevator which is huge compared to the cross section of the elevator which cannot be too big because of a lot of concerns.
In trying to simplify it, I'm imagining a carbon nanotube one molecule thick. Will this be able to support a string around 70,000 Kms ? Counterweights really won't help here since although it shortens the string, it adds mass anyway. Thickening the string to two molecules would double the mass it has to support and so on and so forth. maybe a double tapered shape might work, like two eiffel towers with their bases together to form a diamond like shape, since the middle will be bearing much of the load. This brings another question, how large should this middle be to be able to hold the whole thing together and have the bottom (and top) be of sufficient size still to be of some use. If it turns out it has to be that the cross section in the middle has to be as big as chicago, to get a point in the ground be 3 inches thick, I don't think it will be cost effective.
Of course I have absolutely no background in this and I'm probably just rambling incoherently.
In trying to simplify it, I'm imagining a carbon nanotube one molecule thick. Will this be able to support a string around 70,000 Kms ? Counterweights really won't help here since although it shortens the string, it adds mass anyway. Thickening the string to two molecules would double the mass it has to support and so on and so forth. maybe a double tapered shape might work, like two eiffel towers with their bases together to form a diamond like shape, since the middle will be bearing much of the load. This brings another question, how large should this middle be to be able to hold the whole thing together and have the bottom (and top) be of sufficient size still to be of some use. If it turns out it has to be that the cross section in the middle has to be as big as chicago, to get a point in the ground be 3 inches thick, I don't think it will be cost effective.
Of course I have absolutely no background in this and I'm probably just rambling incoherently.
One of my main questions (or rather, realization) is how exactly the earth's atmosphere comes into play. I mean, with rockets, shuttles, and other vehicles, there's the extreme heat with leaving and entering of the atmosphere. I was always under the impression that to get to "space", you have to go through this extreme hell... but from reading the articles on space elevator, it doesn't look like the designers are too concerned with that?? Is it because the elevator is going so slow that there's no substantial heating?
Yeh, pretty much. Space elevators will have very gradual accelaration compared to rockets, so by the time it's hit a decent speed it's waaaay out of the atmosphere. On the way back, it will start decellarating before it hits the atmosphere, probably going at no more than a couple of hundred kph.
Rockets have to deal with the extreme heat on reentry simply because they need something to slow them down, they don't have a convenient cable to use to decellarate, so they end up hitting the atmosphere at several thousand kph.
Rockets have to deal with the extreme heat on reentry simply because they need something to slow them down, they don't have a convenient cable to use to decellarate, so they end up hitting the atmosphere at several thousand kph.
The cables will be tensioned, not under pressure. the idea is that the earth station will be pulled a bit by the cable (ok, the cable will have enough tension so that even the strongest winds won't change its trajectory by much).
Regarding the speeds - the shuttle's reentry in atmosphere is at a speed near the LEO velocity (several kilometers per hour). The shuttle could slow down using its engines (consuming fuel), or enter the atmosphere at its speed. Considering the costs of bringing fuel to orbit, slowing down in the atmosphere is a much better idea.
Why the rockets accelerate so much at start in the atmosphere? The trajectory is precomputed, and every change of trajectory will burn fuel. So, in the only volume where signifiant trajectory change can ocvcur because of external factors (winds/rain/...), the passage must be the quickest. (Also, changes at the start of the trajectory are the most expensive to undo, fuel wise and time wise). A space elevator has no speed concerns, and no trajectory concerns - it will always arive at the space terminal.
Regarding the speeds - the shuttle's reentry in atmosphere is at a speed near the LEO velocity (several kilometers per hour). The shuttle could slow down using its engines (consuming fuel), or enter the atmosphere at its speed. Considering the costs of bringing fuel to orbit, slowing down in the atmosphere is a much better idea.
Why the rockets accelerate so much at start in the atmosphere? The trajectory is precomputed, and every change of trajectory will burn fuel. So, in the only volume where signifiant trajectory change can ocvcur because of external factors (winds/rain/...), the passage must be the quickest. (Also, changes at the start of the trajectory are the most expensive to undo, fuel wise and time wise). A space elevator has no speed concerns, and no trajectory concerns - it will always arive at the space terminal.
Also, there are things that have a solar orbit (not around the Earth) but intersect the Earth's orbit. Their speed would be much greater than the speed of any satellite around the earth. The Perseids (and not only) comes to mind
What I'd be more worried about is sabotage, terrorism and the intense cost in maintaining a cable that long getting that much use. If NASA cuts corners to meet schedules for the shuttle, imagine the pressure to keep the elevator open for traffic at reduced cost.
And how will they monitor the cable for wear? That's a heck of a lot of wire to eyeball 24/7.
Not saying it's impossible, but the maintence on the project would be astronomical!
The cable is going to get crazy torques on it from wind resistance. Probably need to mount it on a concrete tower instead of the ground up to like 10,000ft to reduce this.
Also, it's gonna get hit by space junk, especially after Curious George's plan to create an orbiting weapons platform to blow up "enemy satellites" goes into effect.
Also, it's gonna get hit by space junk, especially after Curious George's plan to create an orbiting weapons platform to blow up "enemy satellites" goes into effect.
I'm not an expert on space elevators, but if you want to find answers to your questions, a selection of articles and books on the subject, including some from NASA's space elevator research project, can be found at http://www.spaceelevator.com/docs/
I was actually talking about the same thing. The tension will cause pressure on the string. The weight of the string is pulling down due to gravity, and an equal but opposite centripetal force is pulling up. That is a lot of pressure (or tension)
The CN Tower in Canada is over 1800 feet tall, and the new World's Trade Center will be 1776 feet, but yes, 10,000 feet would be quite an extension. However, I don't think the plan actually calls for a 10,000 feet tower, just that the tower be 10,000 feet above sea level, which can be accomplished by choosing the right site.
But those towers are supporting nothing but themselves - not the kind of loads that are likely to be encountered in anchoring the tether. But yea, getting above sea level may be a good idea.
Think of the forces acting on a megalong cable: for one, gravity will pull it toward the earth, granted. The other force is centripital (centrifugal? one or the other... can't rember), which is also pulling the tower toward earth. Basically the momentum of the tower is the only thing keeping it in place. How is that modeled as a force.... my physics notes are at home 
There will be also a "rotating" tendency on the cable, considering that the ends of the cable have different velocities. Also, on masses moving on the cable will be a Coriolis force, that the tension in the cable must neutralize.
The force that tends to move something away from a circular trajectory is called centrifugal. It is nothing else that the inertia. (Centripetal force is the one that keeps the object on its circular trajectory).
The force that tends to move something away from a circular trajectory is called centrifugal. It is nothing else that the inertia. (Centripetal force is the one that keeps the object on its circular trajectory).
Also, manoeuvering at sea a platform with the mass needed to be a space elevator achor won't be easy. The platform must be big enough that waves have almost no effect on it. The bad news is that a ocean storm might make the base non operable for days. Also, storms at sea have sometimes very strong winds, and those could damage the superstructures on the base.
Not sure what you're getting at here. Of course the cable is rotating - about the center of the earth.
Coriolis is zero at the equator.
The Coriolis force acts on the masses that climb or descend. The idea is that a mass in the center of the Earth has zero speed. If we move it to earth surface, its speed will be 450 m/s (or something like that). The inertia that fights against that change of speed is the Coriolis force.
The Coriolis force is 0 at the poles, not at the equator.
About the "rotating" tendency - I might be wrong, I can not imagine a 40 000 km cable in gravitational field with all the forces at work there
The Coriolis force is 0 at the poles, not at the equator.
About the "rotating" tendency - I might be wrong, I can not imagine a 40 000 km cable in gravitational field with all the forces at work there
No. You are wrong.
If the object is moving to north or to south (at the same altitude), the Coriolis force will deflect it as you said (on Equator there will be no deflection).
However, if the object is moving up, the Coriolis force will move it to the west, and if it is descending, the force will move it to the east.
If the object is moving to north or to south (at the same altitude), the Coriolis force will deflect it as you said (on Equator there will be no deflection).
However, if the object is moving up, the Coriolis force will move it to the west, and if it is descending, the force will move it to the east.
Centrifugal force? What force is that?
You can use superconductors to transfer power up the cable, assuming a) we use a HTS (by current standards) conductor and pump liquid N2 around it, or b) we use REALLY HTS conductors.
You can use superconductors to transfer power up the cable, assuming a) we use a HTS (by current standards) conductor and pump liquid N2 around it, or b) we use REALLY HTS conductors.
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