A mass driver or electromagnetic catapult is a proposed method of non-rocket spacelaunch which would use a linear motor to accelerate and catapult payloads up to high speeds. Existing and proposed mass drivers use coils of wire energized by electricity to make electromagnets, though a rotary mass driver has also been proposed. Sequential firing of a row of electromagnets accelerates the payload along a path. After leaving the path, the payload continues to move due to momentum.
Artist's conception of a mass driver on the Moon
A linear motor is an electric motor that has had its stator and rotor "unrolled", thus, instead of producing a torque (rotation), it produces a linear force along its length. However, linear motors are not necessarily straight. Characteristically, a linear motor's active section has ends, whereas more conventional motors are arranged as a continuous loop.
This Line 6 Guangzhou Metro train manufactured by CRRC Sifang and Kawasaki Heavy Industries propels itself using an aluminium induction strip placed between the rails.
A linear motor for trains running Toei Ōedo Line
Close-up of the flat passive conductor surface of a motion control Sawyer motor
The Birmingham International Maglev shuttle
