The EmDrive, which was developed by British researcher Roger Shawyer more than a decade ago, generates thrust by bouncing microwaves around inside a cone-shaped chamber. According to Newton’s third law of motion — for every action, there is an equal and opposite reaction — this shouldn’t work, because there’s no exhaust expelled out of the EmDrive system. (Think about rockets, which get their oomph by blasting superheated gases and other material out of nozzles at high speeds.) [Superfast Spacecraft Propulsion Concepts (Images)]

But the NASA team, led by Harold “Sonny” White of the agency’s Johnson Space Center in Houston, did measure some thrust. Specifically, their EmDrive variant produced about 1.2 millinewtons of force per kilowatt of energy. That’s about 100 times more thrust than solar-sailing spacecraft, which harness the momentum of photons streaming from the sun, are able to achieve, White and his colleagues wrote.

Like solar sails, the EmDrive requires no propellant; a spacecraft equipped with this propulsion system could generate all the microwaves it needs using solar panels. So the EmDrive could make space travel much cheaper and faster, theoretically opening up the heavens to greater exploration, advocates have said.