Check out Fastmhz’s induction launchers (for launching rockets) – “A Ring Launcher is an inductive launcher. When the coil is energized, it creates a strong magnetic field around it. Since this coil is flat and a non-ferrous ring is placed direcly upon it, this magnetic field creates a huge rush of current in the ring itself. This current turns the ring into a strong magnet of opposing force which repels the ring away from the coil at amazing speed! I’ve been using aluminum rings exclusively as they are great conductors and easy to get – take any broken 3.5” hard drive apart to get perfect rings for launching! “ [via] – Link.