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# Global Flywheels

a global system of large scale underground flywheels
 (+5, -8) [vote for, against]

a global civil engineering project, create one or more global flywheels the size/diameter of the earth, the first one being around the equator, for the purpose of storing energy. additional flywheels would be at a slightly smaller diameter and below the initial one. a side benefit would be in transportation, one could "ride" the flywheel to the other side of the earth in a matter of hours. another side benefit is in the event of the detection of a medium sized (ie, not extention level) asteroid on a colision course with a large population center, the flywheels could be made to gradually gyroscopically slow or speed the earths rotation so that the rock hits in the middle of nowhere.
 — JakePatterson, Dec 02 2001

(?) Frame around the Earth in Space http://www.halfbake...tal_20space_20frame
Use this as a flywheel to store energy [neelandan, Dec 03 2001, last modified Oct 04 2004]

From whence comes the energy to spin up this flywheel?
 — phoenix, Dec 02 2001

phoenix, the purpose of the flywheel is to store energy, not generate it. considering that the earths reserves of stored energy (oil) are currently being depleted, we will need some technology to replace that. flywheels are simply the cleanest way to store energy. generating the energy is a seperate problem.
 — JakePatterson, Dec 02 2001

If the flywheel was to be the same size/diameter as earth, it would have to pivot at the earths core, you would have to simply cut the earth into two halves, find a suitable material that would withstand the hideous temperature that exists at the centre of the earth for the bearings, plunder a few nearby planets to get enough steel/exotic metals to make the flywheel, and bobs your uncle. You get my vote, can't think why anyone hasn't thought of this before.
 — arora, Dec 02 2001

 It still takes energy to get the flywheel moving. Where does that energy come from? It's just as simple to use pumps to pump water from a low place to a high place for use in the turbines later, with the excess power. They do that already.

More to the point, where does the material to BUILD them come from? And how does one build concentric rings of material that would be moving so quickly?
 — StarChaser, Dec 02 2001

each wheel would be a ring, not a disk, so it would not need to physically pivot at the earths core. (actually it would be two rings which would counterrotate so the system would not cause the earth to precess unless desired, see my original point about asteroid defence.) gravity would hold the rings in place. the additional wheel systems would be at a lower depth and skewed at an angle to the plane of the original, ie hop on in australia and get off in north america. of course there are other ways to store energy, but no other way also provides the same transportation and asteroid defence benifits that this one would.
 — JakePatterson, Dec 02 2001

any chance of a sketch, Jake
 — po, Dec 02 2001

OK - here's how to get the flywheel moving. The flywheel should have little pop-up sails all around its circumference. The half of the flywheel which is currently travelling away from the sun would pop up all its sails and be pushed round by the pressure of photons from the sun. It would take a while to accelarate up to speed, but (a) there are a lot of photons coming from the sun, (b) it'd be free, (c) it would carry on accelarating ad infinitum.
 — hippo, Dec 02 2001

Okay. I know what a flywheel is and what it does, but:
1) There will (presumably) be a serious delta between the speed of the flywheel and the surface of the Earth (once you get the flywheel moving, and you still haven't answered that one). How will people get from Earth to the flywheel and back?
2) Where will we keep all the satellites?
3) How will a bunch of rings effect the rotational / revolutional speed or axial declination of the Earth? (unless they are extremely massive)
4) How will you explain to your decendants that the stars actually used to be visible from Earth at night?
 — phoenix, Dec 02 2001

phoenix: the rings would be buried. see the sketch. that should answer your questions 1, 2, and 4, but it may well raise different questions. as for 3, they would be extremely massive, but each "ring" would actually be two counter-rotating rings in a pair, which should avoid causing unwanted precession of the earth. operators would only make them mismatch spin when, for some reason, we want the earth to precess. to answer the last part of your question 1, a monorail attached to the side of the chasm wall could accelerate over a short distance near a terminal to match the speed of the ring, and then the passengers could hop from the monorail to the ring itself.
 — JakePatterson, Dec 02 2001

Ah, buried. Missed that paragraph in your description. Doesn't really answer my question about using them for transportation, though. If you have a monorail that can attain those speeds (whatever they might be) why not just stay on the monorail?
 — phoenix, Dec 03 2001

Jake, I think you need to start a wee bit smaller. Would you settle for building a prototype out of the southern polar icecap? I'm thinking just polish the undergirding Antartic continent to be perfectly spherical, then place some kind of semi-concentric rail (or even magnetic levitation) that surround the pole and fit like sandwich meat between the Antartic 'soil' and the Antartic glacier-flywheel. Energy could be stored by making the Antartic glacier spin _slower_ than the earth. Think of it as a giant, non-spinning equivalent to Hoover dam -- except frozen. Hey, does anyone know how superconducting magnets work?
 — pathetic, Dec 03 2001

 — neelandan, Dec 03 2001

Wouldn't there be a problem with the fact that the Earth is not perfectly spherical but squidged on the North-South axis, making it bulbous at the equator? This might raise difficulties in building off-plane rings - i.e. linking Australia and North America. Still... thinking big: I like it. If you can solve the Squidgy Earth Problem, you might just win my croissant.
 — Guy Fox, Dec 03 2001

 If you want to change the earth's rotation, a better method would be just to attach large rockets to the earth pointing along lines of latitude in the appropriate direction. The energy required to get the rings up to speed and to change their rotation would be - well say you have a cross-section of 10 x 10 m, a density of 5000 kg per cubic metre, that's 2e14 kilograms, or the weight of about 400 million jumbo jets. Hmm.

 This might work as a transport device, since the energy cost for carrying a body around the flywheel would be far less than airplanes (which have to carry all that metal and fuel and pilots) or most other modes of transport. Of course, setting the wheel going would be an incredible use of energy [use rockets/atomic bombs?], and I'm not sure what kind of gearing we'd need to keep it going at speed, but the amount of energy required to top it up for each body you send round should be close to the kinetic energy of the body at speed. If we could solve these problems (and the acceleration questions when you go to/from the wheel), this could have uses.

There's been a lot of ideas about orbital platforms, rings around the earth, zero-gravity monorails, etc, posted here, but this actually seems one of the better-worked out ones, despite the formidable construction challenge.
 — pottedstu, Dec 03 2001

Confused. Didn't realise there were so many geologists, engineers and physicists on the HB!
 — sven3012, Dec 03 2001

I'm all for an intercontinental train system as long as the train can float (just in case).
 — phoenix, Dec 03 2001

 So now we need a more-than-two-mile-deep tunnel , a huge amount of energy to get it moving and more to KEEP it moving, and an Earth's worth of Unobtanium to build even the -first- one from.

 — StarChaser, Dec 03 2001

 — po, Dec 03 2001

pottedstu: i was thinking along the lines of not having the rings mechanically attached to anything, they would operate like a giant electric moter/generator. gravity would searve the function that a central bearing would in a conventional scale flywheel/moter/generator. of course, there would still be friction with the air and yes, it would take an immense amount of energy to get it moving, but that is the point of making a flywheel bigger, to be able to store more energy in it. starchaser: instead of making superdeep tunnles, tubes could be constructed through the ocians for the rings to pass through. the passengers could look at the fish. it would be nifty.
 — JakePatterson, Dec 03 2001

I know just the CP3man to test this out UB
 — po, Dec 03 2001

To the question of how to get on and off it, I envision deeply notched surfaces, and people with really long shepherd's crooks. Impractical, yes, but a rather comic mental image.
 — nick_n_uit, Dec 03 2001

You'd end up with all these disembodied arms attached to shepherd's crooks...
 — StarChaser, Dec 04 2001

 ... and then who'd carry the mail?

The sketch is a much better representation of a possible configuration than what I originally thought. Approach Algeria and Libya with the suggestion they each build a small one to link their nations, then see who follows. Maybe Vinci will sign on to build it.
 — reensure, Dec 04 2001

OK, here is another way the transportation aspect might work. you have a "car" on rails above (not attached to) the rings, passengers board, then the car deploys a hook mechinism attached to a really long bungie cord, which hooks to the moving ring. The car procedes to accelerate (which of course will slightly slow the ring, ya cant get energy for free.) A detachment point is calculated based on velocity and breaking distance in relation to the destination. An airplane like wing aparatus could cause the car to levitate off of its resting surface for the bulk of the journey, to reduce friction. If the rings were going fast enough, maybe objects could be flung into orbit using a variation of this method.
 — JakePatterson, Dec 04 2001

Why does the ring need to be got moving? The earth already has around 1000 mph at the equator, which would represent a lot of energy. To change the position of the surface of the earth the flywheel would be slowed down/speeded up to alter the length of the day, conservation of momentum, then the brakes are put on or the motors are run as generators to return to the normal day length.
 — Citizen Rat, Dec 04 2001

[Citizen Rat]
The rings would have to be made to move in relation to the cavern walls in order to use them to store/retreve energy. This would require some way of generaing the energy that you want to store. The statement that "it is already moving" is equivalent to the statement that uncharged batteries "already have electrons" in them.
 — JakePatterson, Dec 04 2001

gab gurd? yup, I didnt think it through, I think that I was thinking that this could only be used to store (or transport) energy.
 — Citizen Rat, Dec 06 2001

The real problem with a global flywheel is outward force of the spin, much like when you hold a bicycle wheel-spin it-and try to tilt it from side to side. The same problem would happen with the global fly wheel; and here is why. When the upper band rotates against the natural spin of the earth as it rotates it would decrease inertia, traveling with the earths spin compounds inertia of earths axis. The wobble of the earth would decrease or increase, and if it was too great it could cause a poler shift or even kick the earth out of orbit. Good idea, bad results.
 — FreeNRG, Apr 30 2002

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