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I invented a flying engine moving entirely by magnetic forces (such as the force related with magnetic field of the Earth).

See http://porton.wordpress.com/2011/12/23/magnetic-vehicle/

The question is, can we build an engine of this type which is enough powerful to actually fly?

The question is both about the mechanical engine described in the post above and about a hypothetical (not developed by me in details) purely electronic version.

My question is: Describe operating characteristics of these kinds of engines.

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We probably could, if it did work in principle; but it doesn't, does it? What makes you think this should fly? There is no net force to the outside, unless you consider higher multipole moments. –  leftaroundabout Apr 9 '12 at 20:45
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4 Answers

up vote 3 down vote accepted

No such engine can exist--unless you custom-tailor your magnetic field.

Any such engine you build will need a current loop--since current requires a closed circuit to flow.

A current loop never has any force on it in a uniform magnetic field{*}. It can have a torque, so at max you can create a device that spins.

If you want something to levitate, you need to generate a nonuniform magnetic field. A large magnet on the ground is one way to do this, but it leads to instability. And you'd have to keep the magnet with you wherever you went, so you effectively have to drag a large magnet along the ground to make a teensy thing fly.

Of course, you can lay out the magnet like a track. Which has already been done in maglev trains.

enter link description here

In a maglev train, there are magnets in the track, and electromagnets at the bottom of the train (or is it the other way around? Doesn't really matter here) The electromagnets rapidly switch polarity.

In the diagram above, you can see that the train will be pushed towards the left. If you think a bit, you way also notice that, due t the symmetry of the situation, once the train is left, it will be pushed towards the right. But, in the time it takes for the train to be pushed left, the polarity of the electromagnets switches, and the train gets pushed further left.

Here, the magnets serve two purpses: they make the train go, and the levitate it (reduces friction). Maglev trains are one of the fastest type of trains and have been in use in many major cities for quite some time now.

*The Earth's field is nonuniform, but locally uniform as long as you don't have any electrical devices nearby. I really don't think that any nonuniformity in this magnetic field could be harnessed to make a flying machine. Then again, I may be wrong about this.

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You say "A current loop never has any force on it in a uniform magnetic field". Is this true even when a part of the wire MOVES? –  porton Apr 11 '12 at 15:32
    
@porton: Yep. Why not? Though if you consider relativity there might be something--either way, the force will be negligible. –  Manishearth Apr 11 '12 at 15:41
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@leftaroundabout is correct; the net force (to lowest order) would be zero, regardless of the amount of current. The only net-force would come from higher order terms (i.e. from the divergence in the earth's magnetic field) ... and thus amounts to a very small effect. Additionally, producing high-power magnetic fields in very difficult and takes a-lot of a very heavy machinery (which is thus, not inclined to fly).

If you're interested in designing a flying machine, you should consider studying aeronautics. If you're interested in electrodynamics, you should consider studying that. In either case, its appropriate to establish a background of basics before you try to make your own creations.

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I think it is entirely possible!!! you just need to use momentum of the magnets to keep the other one going using centrifficle foce as well.There is no law of motion that disaproves this very easily plausible science project.

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I'm no professional. With that said... Using a wireless energy supply from the earths current (Tesla), you could provide quite a load to an electromagnet, used to push one way with displacement on the vehicle (or whatever) while pulling on everything else with mass, from the opposite. Flying saucers I'll bet are shaped that way so the center bubble can swivel as the vehicle turns instantly as all atoms are magnets, and being acted on by the vehicle magnet in the shape of a donut, would all respond instantly, like in a gravitational field. Tune into the scalar waves and away you go..... I'm sure computers can handle the math. Magnets with wireless energy supply.

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energia.sl.pl/propulsion.htm pretty cool –  cameron downie Mar 13 '13 at 5:45
    
Wishful thinking based on complete ignorance of reality. –  hdhondt Oct 16 '13 at 23:35
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