Is a Space Elevator feasible?

[scienceguy]

This had been discussed on other threads so I decided to start a thread for it. Some had said that a space elevator is not feasible because of space debris. Is there any way to prevent space debris from destroying a space elevator tether?

[rdale]

Many threads already exist explaining the pro/con debate. It might make more sense to  look at those first and post more specific questions?


http://forum.nasaspaceflight.com/index.php?topic=20948.0

[scienceguy]

OK a more specific question not asked in the thread you referenced in that of shielding the space elevator from space debris. If we had a material strong and light enough for the tether, wouldn't that material also be strong and light enough to make a huge cylindrical shield to protect the tether against LEO debris?

[colbourne]

The tether has to support the mass of itself and any shielding.
As  we are barely able to make a tether support itself even if tapered, supporting any extra weight,  which is not weight baring is going to be impossible.

A tether could be made with many redundant fibres, so that if one is broken the others share the load when we have strong enough material.

[Jorge]

A tether could be made with many redundant fibres, so that if one is broken the others share the load when we have strong enough material.

For example, the Hoytether:

http://www.tethers.com/Hoytether.html

[MartinRNunn]

So now that you have the material for the tether, you don't have to worry about it supporting itself because the counterweight in orbit will keep it taught.  So now can you make a tether long enough and how do you get it up there?

On the idea that something will hit it in space, why won't what ever hits it just bounce to one side, if a ball hits a string does the string break?

[oiorionsbelt]

The tether as envisioned by Bradley Edwards is a ribbon about a meter wide and as thick as a piece of paper.

As for getting it up there it is proposed to wind it on a spool launch that on a rocket and unwind it as it is 'pulled' back to earth.

[strangequark]

So now that you have the material for the tether, you don't have to worry about it supporting itself because the counterweight in orbit will keep it taught.  So now can you make a tether long enough and how do you get it up there?

On the idea that something will hit it in space, why won't what ever hits it just bounce to one side, if a ball hits a string does the string break?

Ever see a string get cut by a bullet?

[Hop_David]

On the idea that something will hit it in space, why won't what ever hits it just bounce to one side, if a ball hits a string does the string break?

Try throwing the ball at 8 kilometers/second

[zaarin]

Yeah have a solar powered reflector or laser gun or missile array and a radar and anythung that comes into proximity of the line just bast out of the sky wihtout hesitation.

[manboy]

The tether as envisioned by Bradley Edwards is a ribbon about a meter wide and as thick as a piece of paper.

So it would be more like a ribbon?

[Tass]

The tether as envisioned by Bradley Edwards is a ribbon about a meter wide and as thick as a piece of paper.

So it would be more like a ribbon?

Yes.

[watermod]

The question assumes the Space Elevator is for Earth.

I think a space elevator is, near-term, much more useful on the moon or large asteroids.
How much simpler and hopefully cheaper would a moon elevator make mining and base support?

What material would be "good enough" for a moon tether?

Could it be simply made from mining products on the moon?

[Hop_David]

The question assumes the Space Elevator is for Earth.

I think a space elevator is, near-term, much more useful on the moon or large asteroids.
How much simpler and hopefully cheaper would a moon elevator make mining and base support?

What material would be "good enough" for a moon tether?

Could it be simply made from mining products on the moon?

The usual approach for proposed earth beanstalks is to start from geosynch. Then building up and down at the same time. Stalk below geosynch is balanced by stalk above. Earth's geosynch is about 36,000 km above earth's surface.

For a lunar beanstalk, the stable locations that are fixed with regard to the moon are EML1 and EML2. These are about 60,000 km from the moon's surface.

Construction from EML1 and 2 is less stable than construction from GEO. A small perturbation could send an unanchored lunar stalk moon far away from EML1 or 2. Until the stalk's anchored, construction would be vulnerable to catastrophic failure.

[cromandmitra]

What would be  the likelihood of debris hitting a meter wide paper this ribbon(tether) in LEO? Which from what I understand is where most of debris is concentrated.I would believe that the danger would be more so to the space elevator moving up or down through LEO. thought's?

[Hop_David]

What would be  the likelihood of debris hitting a meter wide paper this ribbon(tether) in LEO? Which from what I understand is where most of debris is concentrated.I would believe that the danger would be more so to the space elevator moving up or down through LEO. thought's?

A ribbon only one meter wide would still have much greater cross sectional area than an elevator car.

[synchrotron]

What would be  the likelihood of debris hitting a meter wide paper this ribbon(tether) in LEO? Which from what I understand is where most of debris is concentrated.I would believe that the danger would be more so to the space elevator moving up or down through LEO. thought's?

A ribbon only one meter wide would still have much greater cross sectional area than an elevator car.

And a much much larger swept volume throughout its mission life.

[Nomadd]

 I think all the banter regarding tethers ignores the elephant in the room. Controlling the oscillations in something that long and thin would be so difficult it could be an insurmountable obstacle.

[RanulfC]

I think all the banter regarding tethers ignores the elephant in the room. Controlling the oscillations in something that long and thin would be so difficult it could be an insurmountable obstacle.

From the material I've read it doesn't seem that oscillation control has been found to be a major issue. It is something that has to be considered when designing and buiding the tether (or for that matter most tension structures) but it isn't in any way "insurmountable" and different passive and active methods have been suggested  and tested.

Can you be more specific in your concerns?

I'd also suggest looking over the following sites:
http://spacetethers.com/

and

http://www.tethers.com/

Both of which have a lot of information and resources on tethers and tension structures in space.

For anyone interested in an "overview" of research this 2007 paper has some good information:
http://www.ewp.rpi.edu/hartford/~ernesto/F2011/EP/MaterialsforStudents/Li/Cartmell2008.pdf

Randy

[seminone]

Don't deploy a long cable system of 50,000 km.
Use a different concept that does not have to reach beyond low LEO.

This had been discussed on other threads so I decided to start a thread for it. Some had said that a space elevator is not feasible because of space debris. Is there any way to prevent space debris from destroying a space elevator tether?