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NASA researchers have reported fresh evidence that an "impossible" space propulsion technology might actually work.

A study from NASA's Johnson Space Center in Houston says a microwave thruster system that requires no propellant appears to generate a tiny amount of thrust. If the technology pans out, it could make spaceflight far cheaper and speedier, advocates say. They argue that the thruster harnesses subatomic particles that pop into and out of existence in accordance with quantum physics — a hypothesis that's mentioned in the study.

Researchers have been looking at unorthodox means of propulsion without propellant, ranging from solar sails to quantum vacuum energy to wormholes. Les Bossinas / NASA file

"Test results indicate that the RF [radio frequency] resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and, therefore, is potentially demonstrating an interaction with the quantum vacuum virtual plasma," the researchers wrote in their study, which they presented Wednesday at the 50th Joint Propulsion Conference in Cleveland. [Images: Spacecraft Propulsion Concepts]

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The technology's roots go back to British researcher Roger Shawyer, who claimed his "EmDrive" could generate thrust by rocketing microwaves around in a chamber. Solar power could be used to produce the microwaves, eliminating the neeed for propellant. Many scientists have dismissed or downplayed such claims, saying the system violates the law of conservation of momentum, Wired UK noted in its report on the technology.

In 2012, Chinese researchers said their version of the system could generate enough thrust to power a satellite. Then, an American scientist named Guido Fetta constructed his own device and persuaded the NASA team — which included warp drive researcher Sonny White — to try it out over the course of eight days in August 2013.

The NASA scientists said the device produced 30 to 50 micronewtons of thrust — less than 0.1 percent of the thrust measured by the Chinese, but enough to justify further testing.

— Mike Wall, Space.com

This is a condensed version of a report from Space.com. Read the full report. Follow Mike Wall on Twitter and Google+. Follow Space.com on Twitter, Facebook and Google+.