One hundred million tons of shrapnel-size diamagnetic particles are dumped into the eccentric Earth orbit. The particles form a ring similar to the Saturn ring. An electromagnet rides on the particle stream and transports cargo to space. Additional electromagnets riding on the stream focus the stream; this is called magnetic shepherding. The idea is not workable because micrometeoroids would knock out the particles. The astray particles would collide with the electromagnets at orbital velocity and destroy them. Eventually, the collisions would transform the particles into an opaque cloud which would block sunlight and thereby change the climate of the Earth. The minimum mass is (for 1-ton cargo) 108 tons.
Benoit A. Lebon, "Space Transportation Through Magnetic Shepherding of a Grazing Earth Ring: An Ecological Heart-Shaped Earth Ring by 2010?, Journal of the British Interplanetary Society, Vol. 40, No. 8, 1987, pp. 365-370.
Benoit A. Lebon, "An International Space Telpher System (ISTS) Using an Earth Grain Ring," Journal of the British Interplanetary Society, Vol. 41, No. 11, 1988, pp. 509-518.
The particles are made of mineral ilmenite. Unfortunately, ilmenite is neither ferromagnetic, nor it is a good conductor of electricity. Aluminum would be a much better choice.
The particles must be small to be able to impart momentum to the train. On the other hand, they must be large to keep the correct trajectory despite collisions with the micrometeoroids. These requirements are contradictory. The probability that a meteoroid having mass of at least M grams collides with spacecraft orbiting the Earth equals:
The formula does not include man-made space junk. It was published in: R. L. Bjork, "Meteoroids vs Space Vehicles," Journal of American Rocket Society, Vol. 31, No. 6, 1961.
The drawings included in the bibliography depict curvature of the particle stream in the wrong direction; the stream should pull the electromagnets away from the Earth to counter the force of gravity.