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Space Elevator; A cheap pathway up?
Topic Started: Nov 20 2006, 12:55 AM (1,150 Views)
-JD
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A space elevator would in theory make it easier to send things into orbit by means of a long tether reaching out into space, with a counter weight attached onto the teher, allowing things to travel up by means of centrifugal force. This is only one of the more popular ideas.

So do you think it would be possible? It'd be a logistical nightmare to construct.
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Dr. Jim
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If one can manage to build it the biggest concern would be balance. I'm sure we've all piled things up, and after a few feet it starts to sway. This is especially worrysome with a taller structure, as it would wobble a LOT even without the strong winds.

Then there is the height/rotation issue. The top of the ladder will be rotating behind the bottom as the Earth spins.

Of course, I'm sure there are ways around this.
...Matt was no exception to this. When he stood in the street and noticed his chest started to really hurt again, he made the decision to look down. He screamed like a grown man would scream when that grown man sees a laser burning his chest, and that is like a little girl...
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FallenDeku
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As far as we can tell it would be impossible to build, for it to work it needs to hold its shape, if it changes shape at all then the forces acting on it will change and the whole thing will fall down/apart.

The biggest problem is that the top needs to be travelling so much faster than the bottom, while we can fix this with geostationary orbits we need to worry about the midsection.
If we get the top and bottom going around nicely the middle will be left behind and the elevator will bow out, when it does this the top will be drawn closer to earth where gravity will take it out of the geostationary orbit and the whole thing crashes down.

By the time we consider using rockets down the entire length of the structure to keep it upright it becomes more expensive to operate then a modern fleet of rockets going up and down.
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严加华
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The midpoint is the geostationary (not merely geosynchronous!) point of a space elevator. That's the whole point. The center of mass has to be geostationary. Then you lower the cable from geostationary toward the surface while at the same time building up a tethering mass (either a cable of equal length or a pile of rocks that amount to the same) on the other side to keep the whole thing geostationary.

At this point the only thing that the cable is doing shape-wise is forming a bit of a bow. Winds will deform it, of course, but that's not a problem. There's any number of "ribbon climbers" you can find as childrens toys that can cope with a lot more bending (and even outright folding!) than you'll ever see with a space elevator's ribbon.
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pie is delicious
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Or you could build it entirely out of diamonds. :D
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Necronomicon
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Right element, wrong allotrope. Last I heard, carbon nanotubes were the most popular option for building material.
omar yo. omar comin
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miller
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We should just make a giant slip n' slide to space, but in a tube form, don't ask me how it would work, I just know it would be sweet.
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FallenDeku
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The centre of mass has little to nothing to do with things. A particle (centre of mass) can have a velocity, however it can only have one velocity, the top of the tower and the bottom will be travelling at vastly different velocities, therefore we can't be talking about the same point and the tower can no longer have a centre of mass.
Fact is this does happen on Earth too but because the distances are so small (comparatively) we don't notice it.

Also, if it was moving in a straight line it would work, but this is going to be moving around in a circle. If something moves in a circle it has a changing velocity, if velocity changes that something is experiencing acceleration, in order to accelerate an object requires force to be placed upon it.
Unfortunately for us the Earth's gravitational force does not play nicely for us in this regard and cant be used to accelerate the tower as required, in turn we need to apply force another way and so on and so forth until the project becomes unprofitable.

Now we could get this all to work for us rather nicely if we were to have it hovering above the ground and not touching Earth at all. However there will be some obvious problems with this, namely if the US commits vast resources to it they're unlikely to want the Earth to rotate around and have the space elevator hovering over the middle east for part of every day.
Also the problems we had above with it touching Earth will still occur however this time it will be caused by the Sun (taking into account we don't want to have it sitting in space to be used only once per year as we pass by), granted these effects will be easily manageable.

Another solution to our problem would be to use an infinitely strong material, something that would not bend under the torque applied to it by Earth's rotation. Unfortunately even things like our finest steel are liable to bend like string under these conditions. Carbon tubes are an option, but I don't know anywhere near enough about them to know one way or the other if they could do the job.
Regardless even if the tower itself holds, that force has to go somewhere, namely the ground on which it stands. It is possible it could act like a giant orange peeler and score line around the Earth's surface.
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Malcaor
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I like the iudea of attaching it by a ribbon,a nd having the actual station outside the atmosphere.
It's quite simple: knowledge is power.
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piercehawkeye45
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Would there be anyway of having the station in orbit and then dropping a cable down to a few hundred feet above the surface of the ocean and then attach the space shuttle from there? It would have to be over the ocean so no buildings get ruined if something goes wrong.
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pie is delicious
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If we build it in Antatctica, right on the south pole, it would only spin and the top would not move faster than the bottom. This assuming that we can overcome other difficulties and have it support itself.
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miller
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pie is delicious
Nov 24 2006, 11:04 PM
If we build it in Antatctica, right on the south pole, it would only spin and the top would not move faster than the bottom. This assuming that we can overcome other difficulties and have it support itself.

I like that idea.
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piercehawkeye45
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miller
Nov 25 2006, 01:32 AM
pie is delicious
Nov 24 2006, 11:04 PM
If we build it in Antatctica, right on the south pole, it would only spin and the top would not move faster than the bottom. This assuming that we can overcome other difficulties and have it support itself.

I like that idea.

The construction would be a living hell. I love irony.

1) You would have to find the exact location of the South Pole. Any mistake would result in a tight spiral with a considerable amount of centrifugal force that would surely destroy the structure.
2) You would have to set up a base around the area that would consume astronomical amounts of energy to heat since the -120F (-80C) weather.
3) You would have to find workers that would work in these conditions. A rotation would be needed as well since a couple months in that weather would be extremely unhealthy.
4) You would need to ship and fly all the resources to the South Pole, which will take up considerable amount of fuel and the numerous crashes that will happen along the way.
5) Any problems would go unnoticed for a long time since a quality inspection would be a fantasy. Regular cleaning would be needed and that’s as easy as having a clean car during the dust bowl.
6) Political problems. Who would own it? Who gets to use it?

A very possible solution if you get past the many big obstacles.
Dropped the atomic bomb let them know that it's real
Speak soft with a big stick do what I say or be killed
I'm America!

I have found the enemy and he is us.
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DirkNL
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piercehawkeye45
Nov 25 2006, 07:54 AM
6) Political problems. Who would own it? Who gets to use it?

The penguins own it, everyone knows :D

-Dirk
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pie is delicious
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Most of those problems could be solved by greenhouse gasses. :D
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