NASA's device, a microwave thruster called the "Cannae Drive," was built by US scientist Guido Fetta. It works by bouncing around microwaves within a sealed container, using a method that seemingly contradicts the law of conservation of momentum. Miraculously, the thruster seemed to function as described, and while the model NASA tested is hardly capable of moving any large object through space, the fact that it registered any measurable movement is promising. If the agency can scale up the device significantly, it could be used for anything from limited satellite propulsion that uses solar power exclusively to a spacecraft that can carry astronauts from Earth to Mars in just a few weeks.
source: engadget.com BY Zach Honig