The EmDrive: What Physics Says is Impossible

November 30, 2016 – A paper appearing in the Journal of Propulsion and Power, entitled “Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum,”  represents the first independently published and peer-reviewed verification of the workings of the EmDrive. Considered “impossible,” a  propulsion system that produces thrust with no discernible exhaust and violates Newton’s third law of physics governing conservation of momentum (for every action there is an equal and opposite reaction), the EmDrive has always been considered junk science by many putting it in the same category as “cold fusion.”

Why junk science? Because Newton’s Third Law has been the one that has remained inviolable until today.

The EmDrive, first invented by Roger Shawyer, a Brit, has been subject to testing on numerous occasions. In 2012 a Chinese team published a confirmation that the drive worked but then retracted their paper when flaws were found in their methodology.

But the new EmDrive test used two variables, putting the drive on a pendulum and placing it within a vacuum. With the pendulum any observed swing would indicate the EmDrive was creating thrust. In the vacuum tube the drive was suspended.

What was observed? The EmDrive put out 1.2 millinewtons of thrust, that’s enough to accelerate an object weighing 0.45 kilograms (1 pound) to a speed of 1.6 kilometers (1 mile) per hour in 6 minutes for every kilowatt of power applied to it.

Why is this so odd? An EmDrive has no propellant. It runs on electricity alone. For space travel it means a spacecraft wouldn’t need to carry fuel as part of its payload. Solar panels or a small radioactive energy source could produce thrust.

So how does an EmDrive compare to ion engines like the one used on Dawn, the robotic spacecraft currently circling the dwarf planet Ceres? The thrust of the EmDrive is far less but the ion drive does require a fuel payload to operate.

How does the EmDrive compare to a Hall Effect Thruster, a propulsion technology that SpaceX, China’s national space program, ESA and NASA have all been trying? It provides about 1/50th the thrust. The Hall Effect Thruster still requires a fuel payload but when compared to chemical propulsion needs 80% less on board when deployed.

How does it compare to other zero-propellant propulsion systems such as the solar sail, laser and photon rockets, technologies that require no fuel payload to power them? The EmDrive provides significantly more thrust by a factor of two over solar sails but generates fractionally less thrust than the remaining two.

The authors of the study describe what they witnessed as explainable by using pilot wave theory. An EmDrive serves as a mechanism for electrons and other ionized particles to ride an external wave without application of any other external contributing force. In other words the drive acts as a medium for a physical wave within space to move a particle creating forward or reverse thrust. The position and momentum of the particle is described as a “hidden variable” following a deterministic trajectory guided by the wave within the EmDrive.

View the video to get a better understanding of pilot wave theory. Note the movement of the droplet is similar to that of an electron sandwiched between two surfaces pushed forward by a small pulse of energy from an external source. In the case of the EmDrive experiment described in the paper the external electronic input ended up producing measurable thrust data that varied based on the amount of electrical power being fed to the device.

Are there other explanations for what was observed? The authors of the paper consider several potential error sources, nine in total. One of these is thermal expansion. Doubters have pointed to thermal expansion, the tendency of matter to alter in response to changes in temperature resulting in kinetic energy. Could the EmDrive upon receiving an impulse of electricity be nothing more than a piece of metal warming creating movement of the electrons and ions contained within it? That would meet Newton’s third law.