More than 20 years after its introduction, the EmDrive is still being tested in labs around the world, including DARPA. But the controversial thruster's do-or-die moment is quickly approaching. “We can also get an unmanned probe to Proxima Centauri in a (long) human lifetime, 90 years.” The original EmDrive, built by Roger Shawyer in 1998, is a sealed copper tube (pictured above) wider at one end than the other. According to Shawyer, if you bounce microwaves around inside the tube, they exert more force in one direction than the other, creating a net thrust without the need for any propellant....