OT: About Space Elevators

[dogscoff]

MAybe they yould even use this power that comes down the cable, it just has to be strong enough. Thus you would not need to "ground" it, you channel the current into your battery.

Well, if memory serves me correctly, according to Dr Emmet Brown ot the Back to the Future series, a lightening strike supplies exactly 1.21 jiggerwatts of electricity, which happens to be the exact amount needed to send a sports car into the past. So you could actually go up the cable in Australia at 9 in the morning and come down in Europe at midday in 1955.

Seriously, I should think the cable would actually do away with lightning in the area altogether... As I understand it, lightning is when static electricity builds up at cloud level to such an extent that it has to find the route of least resistance to the ground.
With a permanent link between the ground and all levels of the atmosphere, (and I'm not sure but I think bucky carbon would be a pretty good conductor) surely the static would be constantly conducting itself to ground and so there would never be enough built up to form an arc (lightening). Ummm...

You can tell I haven't studied science in 10 years!

[Spoo]

the static would be constantly conducting itself to ground

Even better for powering the thing if you have a constant current.

[geoschmo]

Well, once again according to the Faq on the website that Baron linked to, the current flow from the electrical diferential would be negligable. They kind of skirt the lightening issue by simply saying the best way to avoid lighetning strikes is to have the cable in an area that has a low histroy of lightening activity. That doesn't really say though what happens if it is hit.

I guess the ribbon itself won't be used for powering the climbers as I thought originally. They are suggesting photo cells on the climbers and use a ground based laser aimed at the cells to power the motors on the way up and down.

Geoschmo

[dogscoff]

Anyone ever read a scifi book called "The Descent of Anansi" (or something like that)? Can't remember the author. It was pretty good anyway. It wasn't exactly about space elevators but at the end of the book they've got these two damaged spacecrafrt joined by miles and miles of ultra strong cable, and they use the difference in orbital speeds at different heights to come safely down into the atmosphere. Same principle that keeps the proposed elevator up, I think.

[Puke]

regarding the revival of old technologies to ferry cargo:

the russians had an old cold-war design for a landing craft / transport that was essentially a giant snubbed-winged jet with its engines on the front. it required very small amounts of lift, because it "flew" on a coushin of air a few (50) feet off the ground.

boeing (or LM, i cant remember) is reviving the project and is developing one that can fly further, faster, safer (and is bigger). it can also accend up to 20,000 feet (wich the russians couldnt, being mostly a landing craft) to fly with conventional air traffic and make use of existing commercial airports. The speed and low fuel consumption (less work to fly low on a cusion of air) is expected to cause a great deal of competition with existing freighters.

regarding high capacity batteries:

both the US and Russia have developed and used nuclear batteries. I would say that is pretty high capacity, though you probably cant re-charge them. if you dumped the electricity back into the power grid of whatever mini-city you had at the base station of the thing, they could probably use a good deal of it.

regarding nanotube conductivity:

it can have properties of either a conductor, or an insulator depending on how it is structured. there was a test that placed one nanotube inside another, and used the inner one to conduct electricity (by pumping electrons down the center of the tube) and the outer on as insulation. so to extrapolate a guess, i think they are all insulative, but if built right, you can shoot electrons through the tubes themselves. (regular conductivity means passing electrons from one atom to the next).

[Baron Munchausen]

Talk about the static discharge is probably because of memories of the tether experiments with the shuttle. This was a deliberate attempt to generate electricity with a conducting cable. I believe carbon nano-tubes are non-conducting. I sure hope so. Given the amount of power that little cable on the shuttle created I'd expect absolutely awesome voltages on a space elevator cable since it would run right through the ionosphere and even the Van Allen radiation belts. If the earth's magnetic field doesn't rotate at exactly the same speed as the lithosphere and the cable conducts, you've just made the largest magnetic generator in history.

[ October 10, 2002, 19:48: Message edited by: Baron Munchausen ]

[geoschmo]

From the High Lift systems FAQ:

Will the ribbon produce an electrical current?
Yes, but on the level of milliwatts.

The FAQ has a lot of answers, but very little detail for those answers. But apparently they have looked at the issue.