NASA has tested a microwave thruster that seemingly violates the law of conservation of momentum. Originally reported by Wired, the technology bounces microwaves around to create thrust. British engineer Roger Shawyer designed the original and dubbed it the Emdrive. If the Emdrive actually works, it could be a game changer in the spacecraft business because it doesn't require propellant. Propellant is heavy, and once a spacecraft runs out of it, it loses the ability to change direction. Space historian Amy Shira Teitel makes an interesting point on the website Motherboard: "If a spacecraft, say a deep space probe like New Horizons, which is less than a year from its encounter with Pluto, didn't need propellant, that extra weight and space could be devoted to scientific instruments, larger solar arrays, or a larger power source." Last year, a Chinese team made an Emdrive and reported that they had created enough thrust to move a small satellite. NASA spent eight days testing an Emdrive that was built by Guido Fetta, an inventor based out of the Philadelphia metropolitan area. The lab detected a thrust of 30-50 microNewtons, about 1/20 of what the Chinese team measured. On a side note, the NASA lab doing the testing is the same one that is trying to develop the Alcubierre warp drive, another pie-in-the-sky idea. We'll know more once NASA publishes everything (right now, only the abstract is available) and outside experts weigh in on the experiment and data.