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So I don't see how this partial magnetic shield by itself could translate into linear motion inside Earth's weak magnetic field (or the Sun's even weaker magnetic field, at Earth's distance).
You can't get something for nothing. The kinetic energy to accelerate the satellite must come from somewhere - presumably the from the current in the coil.
It seems to me that the thing that undoes any attempt to shield part of a circuit so that it becomes magnetically inactive, thereby allowing the other part to exert an unbalanced force, or to be exerted upon by an unbalanced magnetic force, is the very currents that are induced in the superconducting shield by the shielding process. Consider a superconducting tube through which part of a circuit passes axially. When current is turned on in the circuit, in order to block the magnetic field from penetrating the superconducting tube, there must be generated in the superconducting tube a countercurrent running in the opposite direction. This countercurrent runs along the inside surface, creating effetively a coaxial cable. So, far, so good. But the countercurrent runs into the end of the tube, where it must now go someplace. To maintain B = 0 inside the material of the tube, it must turn around and head back across the outside surface of the tube. So that, although the current in the central wire has been made magnetically invisible by the shielding effect, we now have a new equal current running along the outside surface of the tube. This will cause the exposed part of the wire to move one way, and the tube to move the opposite way. The amount of distance that the wire will get using this form of propulsion is limited by the radius of the tube. Not suitable for space flight.
Second criterion: the ratio g/B
The graph suggests that B is comparable to g (to within an order of magnitude).But the scale shows g in m/s2, while B is in μT.To provide comparable units, B should be measured in Tesla.This suggests that the Earth's magnetic field might be about 6 orders of magnitude too weak to do what you want?Also, be careful with the mass of insulation, refrigeration and power distribution for a megaproject like this. Mechanical rigidity is also a problem with something that is long and thin.
Yes, when the electric current flows in the ring circuit, its magnetic field induces electric currents in the superconductive shield. But the direction of this current in one side of the outside surface of shield is the opposite in the other side of the outside surface of shield. So the effect of the terrestrial magnetic field on this current is not an opposed force of the force applied on the naked wire but a torque applied on the shield.
The electromagnetic sail associated with a microwave beam would replace the first stages of a traditional rocket.
What is the propellant?
Quote from: alysdexia on 30/01/2016 07:12:32What is the propellant?There is no propellant. I hope obtain a propulsion with the association of a superconductive ring and a magnetic shield. For more information, you can read the first message of the topic.
I already did. In that message the propellant was the earth.