The EmDrive is the brainchild of microwave engineer Roger Shawyer, who after 40 years with aerospace giants Sperry, BAE Systems and Astrium set out to pursue a remarkable idea: a thruster that can produce a force without any exhaust. The problem with rockets is that they need a reactive mass – something to throw away – so if you’re going to Mars you have to take all the propellants you’re going to need for the whole flight with you.
