Space Elevator: Carbon Nanotubes, Lasers & Beamed Energy

[danlgarmstron]

The tether generally proposed for a space elevator is usually made of carbon nanotubes. However, the lifters themselves are usually powered by lasers or some type of beamed energy.

Two questions:
1. Carbon nanotubes can be very good conductors, why can't they be used to conduct electricity to the lifters?

2. Could the tether itself be used as a power source given the vast potential difference between Earth(ground) and space?

 

[BigSteve]

I'm not sure about your first question.
But as for your second one, there are a lot of papers out there on this topic. And it seems plausible if you had a long enough tether(which you obviously would), but I'm not sure how much power you'd actually receive out of the system.

 

[BigSteve]

" Equally, there is the issue of powering the carriages as they climb into space. “We are thinking of using the technology employed in our bullet trains,” Professor Aoki said. “Carbon nanotubes are good conductors of electricity, so we are thinking of having a second cable to provide power all along the route.” "

http://www.timesonline.co.uk/tol/news/science/article4799369.ece

 

[Brian_C]

Actually, carbon nanotubes in bulk form are piss-poor conductors of electricity. Nobody in their right mind would use them for transmission of electrical power.

Space tethers are simply a horrible idea. No material in existence can withstand the massive tensile forces that would be present in a space tether. It is pure science fiction.

 

[DaveC426913]

Space tethers are simply a horrible idea. No material in existence can withstand the massive tensile forces that would be present in a space tether. It is pure science fiction.

That doesn't make them a horrible idea, it means we have a significant engineeering R&D hurdle to overcome. But projections based on current experiments indicate that we are heading in the right direction - that making a strong enough material is an achievable goal. And the potential payoff is spectacular.

 

[Phrak]

I'm skeptical. Can the experimentally obtained values of carbon nonotubes actually do this? What is the minimum required specific strength (tensile strength divided by density) required to stretch a cable from ground level to geosynchronous orbit without a load?

Do you have a source for strength and weight values, or something?

 

[DaveC426913]

I'm skeptical. Can the experimentally obtained values of carbon nonotubes actually do this? What is the minimum required specific strength required to stretch a cable from ground level to geosynchronous orbit without a load?

Do you have a source for strength and weight values, or something?

It is an extremely hot topic. There are large ad hoc groups of scientists and engineers that are devoting some portions of their lives to exploring it - many people are personally very passionate about it. And there is a metric buttload of papers on this topic and anything space elevator-related.

 

[Phrak]

QUOTE=DaveC426913;2495517]It is an extremely hot topic. There are large ad hoc groups of scientists and engineers that are devoting some portions of their lives to exploring it - many people are personally very passionate about it. And there is a metric buttload of papers on this topic and anything space elevator-related.[/QUOTE]

Thanks. In perusing about the internet, I've now seen that. Wikipedia claims that current specific strength of experimentally tested carbon nontubes is insufficient. The theoretical strength is far higher. But this was the case with boron fiber a few decades ago and nothing came of it. It could be interesting to see how this develops.

 

[dr dodge]

QUOTE=DaveC426913;2495517] But this was the case with boron fiber a few decades ago and nothing came of it..

except the space shuttle landing gear

dr

 

[Gfellow]

Addressing "Wobble"

Of course there willl be vibration in a Space Elevator cable. You can't have a long taught cable without it trying to behave like a guitar string.
Might I suggest dampeners at either end?
As soon as an oscillation starts to build, a 'de-oscillation' computer program instructs the rings holding the cable in place at both ends to shift in the direction of the oscillation, thus causing the cable's movement to dampen.
As with anything new and wonderful, there will be many obstacles - but that is what we hairless monkeys are so very, very good at overcoming.