earth battery

[Wahsapa]

so eventually when space elevators are made out of nano-tubes/machines...well first... whatever 'cable' is used for the space elevator is not suppose to conduct electricty, its suppose to be neutral right? a non-conducting far reaching lightweight cable to haul payloads into space...

but what if you WANT it to conduct electricty/hold a charge... my idea is this:

what if you send one space elevator out from the north pole and another out from the south pole, could you pull a charge? could you some how turn the earth into a giant battery?

 

[Cogman]

honestly I dont believe this would work. Currently the material for the ladder would be Carbon-NanoTubes and this Material does conduct electricity. I really dont know why it has to be non conducting though. One thing I should mention is that carbon nano tubes conduct electricity through the middle of the tube and not the outside.

 

[Machine350]

Can you imagine how long it would take an elevator to go up and down into space, it's like 60 something miles isn't it? That thing would have to be bookin it.

 

[sao123]

At a slow speed of 10Miles Per Hours, the trip could be completed in about 6 hours.
Granted thats approximately 15feet per second, which is still faster than any just about any elevator on earth now, but its about 15-18 times less stressful (forcewise) on the person or cargo than a ride on the space shuttle or rocket trip, which could complete the trip in 20-30 minutes.

(these figures are based on some rough guess numbers without any real physical calculation, so dont crucify me, if their not exact)

 

[Matthias99]

Originally posted by: sao123
At a slow speed of 10Miles Per Hours, the trip could be completed in about 6 hours.
Granted thats approximately 15feet per second, which is still faster than any just about any elevator on earth now, but its about 15-18 times less stressful (forcewise) on the person or cargo than a ride on the space shuttle or rocket trip, which could complete the trip in 20-30 minutes.

(these figures are based on some rough guess numbers without any real physical calculation, so dont crucify me, if their not exact)

Keep in mind it's only *acceleration* that imparts any kind of force on you, not speed. A .1g (~1m/s^2) acceleration for a couple minutes on each end (similar force to standing in a regular elevator) would have you moving at several hundred miles per hour with no real impact on the occupants. An airplane takeoff is ~1g (tolerable but uncomfortable over time), and the shuttle is ~3-4g (only tolerable for VERY short periods), IIRC.

 

[DrPizza]

Don't forget that at a certain altitude on the elevator, you are essentially in free-fall. (you feel weightless)

Because of the spin of the earth, as you increase the radius, your horizontal speed is also increasing.

 

[Armitage]

You can't put a space elevator at the poles, it has to be on the equator.
The space elevator is essentially a very long satellite orbiting the earth with its center of gravity at geosyncronous altitude. Because the CG is at geosync, it isn't moving WRT the earth, and you can, in theory, anchor one end and haul stuff up & down.

But any orbit has to be coplanar with the CG of the primary, so an object can't have a stationary orbit over any point but the equator.

 

[Armitage]

Originally posted by: DrPizza
Don't forget that at a certain altitude on the elevator, you are essentially in free-fall. (you feel weightless)

Because of the spin of the earth, as you increase the radius, your horizontal speed is also increasing.

Not until you reach geosyncronous altitude (about 42K KM). Your velocity while hanging onto the tether doesn't match the orbital velocity for your altitude until you reach that point.

 

[Armitage]

Originally posted by: Machine350
Can you imagine how long it would take an elevator to go up and down into space, it's like 60 something miles isn't it? That thing would have to be bookin it.

That's actually a plot point in A. C. Clarke's book Fountains of Paradise where he explores the space elevator concept. But I won't spoil it for you

 

[sao123]

Keep in mind it's only *acceleration* that imparts any kind of force on you, not speed.

For the moment forget the start and end points...
Even at a constant velocity moving in a Y axis from the surface of the earth, you are still applying an accelleration force to the cargo on the elevator. That being equal to G(h) the gravitational force at height h. Remember you are fighting gravity, the whole way up until you get to orbital altitude.

In order to start or accelerate upward velocity, you would have to apply a force G(h) + some additional force F for Y axis acceleration. This in effect means you are constantly having applied accelleration until you reach orbital altitude and velocity.


My approach for such a slow velocity (although the same work is being done) would hopefully be more efficient and less wasteful of mechanical energy. The most efficient values for the acceleration curve would of course have to be calculated.

 

[bobsmith1492]

Technically, that's not true, SAO, but it sort of is. When you are moving at a constant velocity there is no acceleration on your body. However, there is always the acceleration due to gravity; there is also the force of the elevator pushing up on you. Hence, these forces cancel out leaving no acceleration, only the force between your feet and the elevator which would be the same as you feel now, here on earth. This assumes a constant velocity, such as during the most part of said elevator trip.

 

[Wahsapa]

Originally posted by: Armitage
You can't put a space elevator at the poles, it has to be on the equator.
The space elevator is essentially a very long satellite orbiting the earth with its center of gravity at geosyncronous altitude. Because the CG is at geosync, it isn't moving WRT the earth, and you can, in theory, anchor one end and haul stuff up & down.

But any orbit has to be coplanar with the CG of the primary, so an object can't have a stationary orbit over any point but the equator.

so theres no way you can have space elevators at the poles?

 

[MobiusPizza]

Yes you can have elevators at poles. But as Armitage mentioned, whatever you send to orbit would not have geostationary orbit. This means there's no point building one. Plus it is imposible to build such huge project in remote area, also north pole does not have a landmass, and the environmental impact would be huge. Well there's no point to build one to start with so.

I don't get your battery bit. Even you send space evators high up, how can you turn the Earth into a battery? Batteries work by storing charge turning Electrical Energy to Chemical Energy. The Earth does not have a way to turn Electrical Energy to Chemical Energy hence to store charge as a capacitor does. Even if you supply electrical energy to earth, no charge can be stored. And remember electrons are not generated. Everything connected to Earth must be neutral. The electrical socket at every houses are literally connected to the earth. Any charge, positive or negative put on it will be neutralised.

 

[Armitage]

Originally posted by: AnnihilatorX
Yes you can have elevators at poles. But as Armitage mentioned, whatever you send to orbit would not have geostationary orbit. This means there's no point building one. Plus it is imposible to build such huge project in remote area, also north pole does not have a landmass, and the environmental impact would be huge. Well there's no point to build one to start with so.

No, it's not possible. A space elevator is an orbiting structure. You can't have an orbit that places an object motionless over an place other then the equator. A space elevator is only remotely possible because it's a tension structure rather then a compression structure. The bit past geo is pulling away due to centripetal force, the bit below geo is pulling down due to gravity. No compression.

I don't get your battery bit. Even you send space evators high up, how can you turn the Earth into a battery? Batteries work by storing charge turning Electrical Energy to Chemical Energy. The Earth does not have a way to turn Electrical Energy to Chemical Energy hence to store charge as a capacitor does. Even if you supply electrical energy to earth, no charge can be stored. And remember electrons are not generated. Everything connected to Earth must be neutral. The electrical socket at every houses are literally connected to the earth. Any charge, positive or negative put on it will be neutralised.

What he really means is generator. If you move a conductor through a magnetic field (such as the earths magnetic field), you generate a current. It's been done in tethered satellite experiements. But back on topic, I'm suspect that you actually wouldn't want the elevator at the pole for this to work ... you want the conductor moving through at a right angle to the magnetic field, so actually an elevator on the equator might be exactly what you want.

But, moving the conductor through the electric field generates a current and a force on the conductor. Which is definitely something you DON'T want on your space elevator.

 

[MobiusPizza]

Ah I get this now. Hm from what I've read I thought space elevators are rigid structures with support from the ground rather than floating and orbiting ones. The structure is constructed with light weight but strong carbon nanotube. If it is supported at the ground then you can definitly build it at the poles. hm...

Well the magnetic field rotates together with earth so if the elevator is geo stationary then the field would sppear to be stationary I think.

 

[Armitage]

Originally posted by: AnnihilatorX
Ah I get this now. Hm from what I've read I thought space elevators are rigid structures with support from the ground rather than floating and orbiting ones. The structure is constructed with light weight but strong carbon nanotube. If it is supported at the ground then you can definitly build it at the poles. hm...

The current tallest bulding in the world is the CN Tower at just over 0.5KM Something tells me that extending that by orders of magnitude isn't really feasible or it would be done by now. A space elevator is a completely different animal. So, you can build up to about 0.5 KM, or you can maybe build to > 42K KM Nothing in between

Well the magnetic field rotates together with earth so if the elevator is geo stationary then the field would sppear to be stationary I think.

Yea, I was wondering about that ... there's a guy in my office that would know about that stuff, but he's out today.

 

[imported_StormGod]

Originally posted by: AnnihilatorX
Ah I get this now. Hm from what I've read I thought space elevators are rigid structures with support from the ground rather than floating and orbiting ones. The structure is constructed with light weight but strong carbon nanotube. If it is supported at the ground then you can definitly build it at the poles. hm...

Well the magnetic field rotates together with earth so if the elevator is geo stationary then the field would sppear to be stationary I think.

I know the the current most-likely model which was discussed the the 3rd annual space elevator conference at Sandia National Laboratory was the tethered string type. This works in exactly the same way that you can swing a bucket full of water in a circle and not spill any. Centripital forces greater than the pull of gravity result in a net force acting on the water normal to the bottom of the bucket, thus there is no place for it to escape. With the space elevator what is proposed is a very long string with some appreciable mass at the end. If the string is long enough and the mass at the end great enough, then a car can climb the string (probably a carbon nanotube belt actually).

As correctly mentioned strings of infinite length can be placed in tension, but a structural member of this length in compression/shear is unthinkable right now. It would require an amazing advance in technology to consider this type of system. This was actually slash dotted recently but I can't find the story any more. Here is another link though.

 

[Armitage]

Originally posted by: StormGod

Originally posted by: AnnihilatorX
Ah I get this now. Hm from what I've read I thought space elevators are rigid structures with support from the ground rather than floating and orbiting ones. The structure is constructed with light weight but strong carbon nanotube. If it is supported at the ground then you can definitly build it at the poles. hm...

Well the magnetic field rotates together with earth so if the elevator is geo stationary then the field would sppear to be stationary I think.

I know the the current most-likely model which was discussed the the 3rd annual space elevator conference at Sandia National Laboratory was the tethered string type. This works in exactly the same way that you can swing a bucket full of water in a circle and not spill any. Centripital forces greater than the pull of gravity result in a net force acting on the water normal to the bottom of the bucket, thus there is no place for it to escape. With the space elevator what is proposed is a very long string with some appreciable mass at the end. If the string is long enough and the mass at the end great enough, then a car can climb the string (probably a carbon nanotube belt actually).

Yep ... the key being that the CG is at GEO. You could either put a big honkin mass just outside geo, or a smaller mass further out.

As correctly mentioned strings of infinite length can be placed in tension, but a structural member of this length in compression/shear is unthinkable right now. It would require an amazing advance in technology to consider this type of system. This was actually slash dotted recently but I can't find the story any more. Here is another link though.