Why can't you use earths magnetic force as propulsion?

Question

I was thinking about how you could create a hover craft that would fly without wind or air and I was wondering why you can’t use magnets to repel off the earths own magnetic field. I figured that it’s maybe because the magnetic field of the earth does not generate a force greater then the gravity from its mass. Do I not know enough about the nature of magnets and magnetism? Is completely stupid?

Earths field is enought to push away solar flares (I know they're charged particles) and gravity increases in fourths as you move toward it (vice versa when moving away). Why not a super magnet to push off earths magnetic field, one that compensates for changes in polarity.

Answer 1

A locally generated magnetic field, when placed in an external magnetic field will indeed exhibit a net force on it. Unfortunately, the force is proportional to the dipole moment of the local field times the *gradient* (spatial derivative) of the external field. Not only is the earth's magnetic field weak, it varies very slowly with position. So, the net force on your craft is negligible.

Note that compasses work due to the *torque* on a dipole due to the earth's field. The torque is proportional to the external field directly (not just its gradient), but there is no significant net force on the needle - just torque. So, if all you're concerned with is aligning your craft northward, then it might work.

The force on a charged particle in a magnetic field is proportional to its velocity and *perpendicular* to its direction of motion, so it does not increase its speed (just direction).

Answer 2

Okay I see and hope you all know you outrank my intelligence, so please give me some grace here.

If the craft could create a magnetic resistance field greater than the earths, having the ability to manipulate with great forces could that not accomplish such?

It seems to me getting stuck on using the earth you would want to use any gravitational pull caused by mass and measure that and then create a force that not only equals it but is far greater but focus it as an opposing force. You could even focus it on other objects that may have great density and thus giving it the ability to move in any directions while bouncing off mountains and if strong enough other heavenly bodies such as our moon.

Again, just a non educated guys thinking, so please tell me in laymen s terms how this might work. It would seem possible.

Answer 3

You are confusing magnetism and gravity. The earths magnetic field is only strong enough to move the needle on a compass. Gravity on the other hand is powerfull and we have used it many times to slingshot satellites out into space at speeds unobtainable with rocket power.

Answer 4

The earth's magnetic field is not strong. It is almost always strong enough to encapsulate the earth in the plasma emanating from the sun, but occasionally it isn't - witness the disruption of electric grids that sometimes happens during solar flares.

Answer 5

it is obtainable, besides the undeniable fact that it may require the two a million) decreased gravity, as in severe elevations/bordering area point or 2) unholy quantities of ability. i think you're observing something alongside the traces of an area tether.