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Where do you go to find multi-disciplinary reference material in engineering? Answered

I read this article about the conductivity of carbon nanotubes, and I had the most awesome dream about a space elevator. In the dream it had 2 cables instead of one, and just ran the current through the cables. Anyway, I was sure someone else would have thought of that, so I checked for some reference material. There was a decent wikipedia article which brought up a question. How does current flow affect the yield strength of a material?

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rickharris

8 years ago

Electrical current flowing through a conductor effects it in only 2 ways.

1. There is a magnetic field developed in according with Flemmings laws.

2. As no conductor has zero resistance there are heat losses over the length of the cable. The higher the resistance the greater the heating.

Other than this the flow of electrons does not materially effect the conductor.

HOWEVER. There are many considerations to do with building a space elevator, and quite a few companies trying to be the first to do just that.

The weight vs tensile strength of the cable would become a limiting factor.

The resistance of the cable to electrical flow, a fairly successful prototype uses a laser to power the module, sunlight may be another option.

The effects of the rotation of the earth, the effects of weather

The safety aspects of a cable 100s of Kilometres long hanging in the air.

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steveastroukrickharris

Answer 8 years ago

Superconductors have zero resistance, by definition.

A lot of research has been done on the safety aspects of the design - and its many thousands of km long, not hundreds, since the anchor weight has to be in Clarkian orbit. It is predicted that the cable largely burns up on "reentry" even in the worst case snapping.

Carbon nanotubes easily have the theoretical strength to weight ratio needed for a valid design.

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rickharrissteveastrouk

Answer 8 years ago

Trick keeping a super conductor at liquid helium temperatures over the length of the cable (1000's typo) !! You may as well suggest the cable is made from synthetic spider silk extracted from the milk of genetically modified goats.

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steveastroukrickharris

Answer 8 years ago

Who said it'll need liquid helium ? We can make LN2 superconductors already - there are hotter ones yet, maybe there is a room temperature plateau somewhere.

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Re-design

8 years ago

Wow, what a great question.

I have no idea but I'm going to say from intuition that it has no effect until current flow causes significant heating.  That's my GUESS so don't take it to the bank.

I'll be watching this question to see what some of the other educated provide to your question.