Space elevators and plate tectonics

[ajtribick]

Because the Earth's surface consists of a bunch of moving plates, presumably the base station of a space elevator is going to eventually be moved to a location off the equator, which would be problematic after a while. Long lengths of space elevator crashing to the ground could be rather annoying for those in the vicinity.

Presumably this would take a long time to be a significant effect though given that the plates - some figures I've seen suggest that the maximum velocity of the plates is ~10 cm/year, and the direction of the plate movement probably won't be exactly north or south. How far off the equator do you have to get before the space elevator starts getting problems?

[rthorvald]

Because the Earth's surface consists of a bunch of moving plates, presumably the base station of a space elevator is going to eventually be moved to a location off the equator

Why not build it on an artificial floating island? After all, most of it will hang down from space, not grow upwards...

-rthorvald

[Dollan]

If the average movement rate of tectonic plates is equal to that of the growth of your fingernails, I doubt that it would become a significant problem at all. A civilization that remains extant on a geological time scale will likely have moved beyond the need for a space elevator, or will have learned how to maintain its position.

...John...

[eburacum45]

This is the base of my space elevator model; based on an idea by Dani Eder, it is a 15 kilometer high tower made of lightweight but strong materials, taking the elevator above the most active part of the atmosphere.


It would be difficult to move such a large structure to accomodate plate tectonics; but it probably isnt necessary. The elevator cable is flexible, and can accomodate a fair amount of movemet at either end. If the base moves a centimetre in a hundred years, after a million years the base will only have moved ten kilometers.
But the elevator is 35 thousand kilometers long; this movement would only cause the elevator to hang a fraction of a degree off the vertical.

[speedfreek]

Maybe I'm missing a fundamental aspect of space elevators or something, but would't it just be easier to adjust the position of the thing at the other end of the elevator, to reposition it above the base station?

[selden]

The upper sections of a space elevator are in geosynchronous orbit. If they're not positioned exactly over the equator, they'll be trying to go equal distances north and south of the equator. That'll cause extremely large strains if it's a very large excursion.

[speedfreek]

Ok, so I was missing a fundamental aspect of space elevators!

[t00fri]

Ok, so I was missing a fundamental aspect of space elevators!

I am also missing some fundamental aspects of space elevators!

Bye Fridger

[scaddenp]

UP TO 10cm of movement is recorded at plate margins and is the movement
of one plate with respect to the other. The vector of movement of a plate with
respect to the rotational pole is another matter.

[selden]

I really don't think you want the base of a space elevator to be in an area that's techtonically active, especially not near the edge of a plate. Earth/seaquakes and volcanoes wouldn't be good for business...

Fridger,
I'm not quite sure what kind of comment you're trying to make. Once it's in place, a space elevator should be able to provide a very inexpensive means of putting things in orbit. Until recently the strength of material needed seemed to require what's commonly called "unobtanium." Recent developments in carbon nanotubes seem to make it not quite so unobtainable, however.

[t00fri]

I really don't think you want the base of a space elevator to be in an area that's techtonically active, especially not near the edge of a plate. Earth/seaquakes and volcanoes wouldn't be good for business...

Fridger,
I'm not quite sure what kind of comment you're trying to make. Once it's in place, a space elevator should be able to provide a very inexpensive means of putting things in orbit. Until recently the strength of material needed seemed to require what's commonly called "unobtanium." Recent developments in carbon nanotubes seem to make it not quite so unobtainable, however.

I was just not informed at what stage of feasability such a challenging project actually was. I have been reading about such plans since a long time, yet it was always closer to SF than reality.

Bye Fridger

[rthorvald]

I was just not informed at what stage of feasability such a challenging project actually was. I have been reading about such plans since a long time, yet it was always closer to SF than reality

Well, i wouldn??t invest my money in it quite yet, but it is certainly fun to see:
http://www.liftport.com/

-rthorvald

[Scytale]

I was just not informed at what stage of feasability such a challenging project actually was. I have been reading about such plans since a long time, yet it was always closer to SF than reality.

Bye Fridger

umm... don't mean to hijack... but what about the giant mag cannon? that seams more realistic to build than the space elevator... why aren't they tackling that first?

[selden]

There's not just one "they" involved in space technology, and different people have different interests.

I suspect building a cannon of any type might run into problems with military technology embargos. Not to mention that the acceleration is a killer. Literally.

Also, you can start on elevator development with a much smaller investment. It seems that several companies are competing to do it.

[Scytale]

Well leaving the military aspect aside for a second (you get an international consortium to build it somewhere in the french guyana or something), and considering that the purpose of such a device would be to put cargo into orbit cheaply, not people, it seems to me that the difference between the magnetic cannon and the space elevator is that the technology is already there.

AFAIK space elevators need supertensile materials, and the infamous carbon nantubes barely cut it - even so they're a bitch to make. For a mag cannon you need magnets + tunnel + electricity + a simple and robust capsule.

I'm just saying, given that people definitely need to reduce orbital lift costs for cargo, I can't figure out why most of the community is interested in something which is yet unfeasable when they could just pick a shovel and start digging the tunnel. Unless, of course, the mag cannon is more unfeasable than the elevator.

[rthorvald]

I can't figure out why most of the community is interested in something which is yet unfeasable when they could just pick a shovel and start digging the tunnel

Well, here you have it... Notice the huge bullet just lifting off the ground...
http://www.noreascon.org/retroart/image ... on-300.jpg
- rthorvald

[selden]

My impression is that the use of rail guns for launching satellites is receiving just as much attention as elevators. See, for example, http://www.powerlabs.org/railgun2.htm
and
http://www.astronautix.com/lvs/sharp.htm

[scaddenp]

Hmm, the advantage of space elevator is that you can reduce the energy
cost for lift by using the returning load to assist. You dont get this option
with a ballistic system. Both are better than rocket in not having to lift
fuel though.