There are one or two perennial scientific stories that sound just too good to be true, but if they delivered on their promise would represent a huge breakthrough and instantly obsolete entire fields. One example is so-called “cold fusion”, the idea that nuclear fusion could be sustained with a net energy release at room temperature rather than super-high temperature akin to that of the sun. We all wish it could work, but so far it has obstinately refused. As a TV actor portraying a space engineer of the future once said, one “cannae change the Laws of Physics“.
Another field of scientific endeavor that seems to push the bounds of credibility but is cautiously showing signs that it might deliver some of its promise is the EM drive. Take a metal cavity in the shape of a frustum (A cone with the point removed), and put a piece of dielectric material on the inside of the smaller circular end. Generate an RF field within the cavity, and there appears to be a small but measurable force exerted from its smaller end. This amounts to reactionless thrust, which is to say that there is no ejection of mass as you would see with a conventional thrust engine. Going back to those unchangeable Laws of Physics, either a process is at work that goes beyond current understanding of those laws, or people are being hoodwinked by things that are explainable through other means. Unsurprisingly, there is considerable work underway from teams of scientists around the world to investigate the phenomenon.
The most recent piece of this work that we can examine has just been published by a team working at NASA’s Eagleworks at Johnson Space Center. Their paper, “Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum“, details their experiments with a frustum cavity on a low-thrust torsion pendulum in a vacuum. They present the interesting conclusion that their apparatus “is capable of consistently generating force at a thrust-to-power level of 1.2±0.1mN/kW1.2±0.1 mN/kW“. That’s a tiny amount of thrust for a lot of applied power, but for those wishing for a future in which EM drives might play a part it comes as an encouraging finding.
The paper is a fascinating read as it details the cavity, electronics, and experimental procedures before discussing some of the possible mechanisms. We are not quantum physicists here at Hackaday, so if there is anyone among our readership with a suitable background who would care to explain in our comments section some of the discussion, we would be very interested to read it.
We’ve discussed EM drives before, and one turned up as a Hackaday Prize entry. Will we be covering many more in the future, or do you think we’ll be writing one day about the paper that proves them to be a false hope?