Reactionless thrusters

Reactionless thrusters have been a convenience of science fiction for decades. After all, the plot mechanics of a novel are simplified if the spaceship never has to worry about running out of propellant.

Now, researchers in China claim to have developed a scaled prototype of a microwave relativity engine that functions as a reactionless thruster. Energy goes in via microwaves, they bounce around for a while in a resonance chamber... and that's it.

No propellant expelled, no fuel gets used up. As Galileo would say, "Eppur si muove."

I'm going to go ahead and call BS on this, not merely because this violates the laws of physics as we understand them and because Boeing Aerospace worked with the lead inventor for a while then scrapped the project. My rejection is based on two things:

1. Chinese scientists are always coming out with amazing, revolutionary, miracle stuff which seems to work only in China.
2. The thrust is toward the wide end of the resonance cavity. This suggests that the effect observed is not a quantum force imbalance but the result of outbound radiation pressure. Nifty, but not revolutionary and not something that would work in outer space.

I recall reactionless thrusters making an appearance in Ringworld, one of the classics of science fiction. Larry Niven showed a perfect understanding of the system when he had Wu embed his scooter in the middle of a flying castle. With no propellant exhaust, the thruster can be in the center of mass of your object. This makes steering much easier.

This EmDrive is a nice bit of science fiction. It'll be fun to watch the media reaction until this gets disproven.

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