As clean as electric aircraft can be, there's still one kind of pollution they still produce: noise. Even that might go away before long, though. MIT researchers have successfully flown an ionic wind-powered aircraft that doesn't use any moving parts. The 16-foot wide machine stays aloft by charging wires with a high enough voltage (40,000V) that they strip negatively-charged electrons from air molecules, which are promptly attracted to negative electrodes at the back of the aircraft. The collisions from that newly-formed ionic wind create the thrust needed to keep the vehicle airborne.