space elevator and ionoshphere

[mee]

would a space elevator short circuit the 250,000 volt difference between the earth and the ionoshere making it dangerous?

[enigma]

I don't know about short circuit. A space elevator would have a pretty high resistance.

Do you have a source on the 250kV number? If that's the voltage, then the elevator would probably get quite hot!

[mee]

I don't know about short circuit. A space elevator would have a pretty high resistance.

Do you have a source on the 250kV number? If that's the voltage, then the elevator would probably get quite hot!

I'm sorry, I don't remember the name of the show but it was on television about an hour ago. Probably on the science channel. It also was not mentioned in passing but specifically pointed out with diagrams.

[drag]

Never heard of this. But hey, if it's true, it could be a great way to make
power ! :cool:

[LunchBox]

I'm sorry, I don't remember the name of the show but it was on television about an hour ago. Probably on the science channel. It also was not mentioned in passing but specifically pointed out with diagrams.

Always remember that something appearing in print has no relevance on its being true or not.

[mee]

Always remember that something appearing in print has no relevance on its being true or not.

It was not actually in print. Also, being on a television documentary doesn't necessarily make it suspect either.
:rolleyes:

[GENIERE]

linky thingy (http://www.space.com/businesstechnology/technology/space_elevator_020327-1.html) It was not actually in print. Also, being on a television documentary doesn't necessarily make it suspect either.
:rolleyes:

Actually it was well covered in the press one or two months ago. Maybe it was overlooked by some due to the conventions. Here’s one site linky thingy (http://www.space.com/businesstechnology/technology/space_elevator_020327-1.html) or do your own Google for "space elevator". The proponent wants to use carbon-nanotube-composite ribbon for the needed strength.



http://www.space.com/businesstechnology/technology/space_elevator_020327-1.html

[Ivan Seeking]

I don't know about short circuit. A space elevator would have a pretty high resistance.

Do you have a source on the 250kV number? If that's the voltage, then the elevator would probably get quite hot!

In his Lecture series, Feynman indicates a typical value of 400,000 volts potential between sea level [in a clear atmosphere] and the region at about 50,000 meters. At lower altitudes we find a gradient of about 100 volts per meter on a clear day.

I don't think the carbon materials considered for a cable are conductive.

[enigma]

At lower altitudes we find a gradient of about 100 volts per meter on a clear day.


:surprised Whaaa?

That's not right...

[Ivan Seeking]

:surprised Whaaa?

That's not right...


It sure is. See Feynman. [Edit: Book II, page 9-1; sixth printing, 1977.]

There is a nice experiment to demo this fact. Fill a metal bucket with water and hang it from a tree using a good insulator. Poke a small hole in the bucket and allow the water to drip. The bucket will acquire a charge of about 100 volts per meter above ground level [in ideal conditions] as a result of the excess charge carried away by the water droplets. Note that this can result in dangerous shock depeding in part on the size of the bucket.

[Ivan Seeking]

I should add that this lower altitude potential is not going to induce significant current flow. The ionic rain that falls in accordance with this only carries a current density of one micro-micro amp per meter squared. So the potential would only matter when you reach the ionosphere, AFAIK.

Note that the people who launch model rockets loaded with trailing wires which induce directed lightning strikes, only launch when an ambient electric field strength of about 30KV/meter is measured.