The EmDrive design was ruled theoretically viable by NASA physicist Harold “Sonny” White, even when it seems to violate the laws of physics.
Designed over a decade ago by Roger Shawyer and developed by NASA’s Eagleworks division, the EmDrive bounces microwaves inside a cone-shaped chamber, which would result in thrust, propelling the spacecraft in a certain direction. According to Newton’s third law of motion, this mechanism should not work because there should not be any exhaust coming from the EmDrive system.
This can be compared to the thrust mechanism of rockets, which have their fuel combustion take place in a chamber while the blast passes through the thrust engines.
In the study, the EmDrive produced 1.2 millinewtons of force per kilowatt of energy, being a hundred times more powerful than solar-powered engines.
Implementing the EmDrive on a large scale could make long-term space travel much more efficient, allowing for the expansion of our boundaries of space exploration. China has also been working on its own EmDrive, but the test results were faulty due to measurement error.
EmDrive: Defying the laws of physics
Newton’s third law dictates that, in a closed system, total momentum remains constant. This implies that whenever two particles interact, the forces that appear add up to become equal and opposite to each other. This principle has been shown to remain active even with the most complex of forces and interactions between particles. Even if there are thousands of particles, the momentum exchange between each pair of particles should add up to zero.
Although the study deemed the theory as viable, a long testing process must take place before the engine gets implemented in any real mission. To avoid any probable source of error, the engine must be tested so any variable is accounted for. For example, the engine is expected to heat up as it propels the rocket, which can lead to the expansion of materials, thus becoming potentially disastrous.
EmDrive stands for electromagnetic propulsion drive. The engine would require no propellant and no exhaust exit. Even if it may seem that the EmDrive performs a “reactionless” process, the truth is that its thrust may come from radiation pressure, or as Eagleworks puts it “quantum vacuum virtual plasma,” which is the result of the imbalance caused by the protons crashing against the chamber’s walls, which in turn generates thrust. Although the existence of quantum vacuum is confirmed, there is still no evidence that it allows radiation to push against any sort of “plasma.”
Radiation is the key
Because the theory behind EmDrive’s functioning is so bizarre, physicists argue that it serves as evidence for a different type of inertia which involves something known as Unruh radiation, which originates from the heat emanated by accelerating particles.
According to Mike McCulloch from the University of Plymouth, the EmDrive’s chamber is the perfect place for Unruh radiation waves to occur, as the inertia of the photons within the chamber becomes erratic as they bounce against the walls.
The ‘impossibility’ of EmDrive does not stop here since the theory of Unruh radiation would also suggest that in such scenario it would violate Einstein’s theory of special relativity.
First described by Stephen Fulling in 1973, Unruh radiation or the Unruh effect determines the temperature of the uniformly accelerating measurement of combined effects in a vacuum field, using the Planck constant, the Boltzmann constant, and the speed of light constant as it appears in Einstein’s equations. The Unruh temperature uses the same expression for Hawking’s proposal for the temperature of a black hole, which was coincidentally formulated in 1974.
For an accelerating observer, W. G. Unruh demonstrated that the state of minimal energy under radioactive inertia would be observed as a warm gas. This interpretation of the measurement of combined effects for the accelerating observer is controversial at most, seeing that some physicists argue that it has already been observed, while others assure otherwise. The main point of discussion is that skeptics believe that the Unruh effect does not emit protons. Proponents claim that Unruh radiation accelerates subatomic particles to relativistic speeds, allowing the ionization of materials.
Alpha radiation, for example, is comprised of alpha particles, or helium-4 nuclei, which consist of two protons and two neutrons. These particles interact with matter due to their significant electromagnetic charge, although they are not capable of penetrating, for example, human skin.
Alpha particles are present in cosmic rays, which could be used by the EmDrive to propel itself through space, just like it would do with solar energy. The sun emits free protons thanks the solar wind, and deep space particles are also mostly protons and alpha particles since they are the remainders of exploding supernovae.
The team publishing the results of the study acknowledged that there could be at least nine potential sources of errors, including radioactive leakage and intrusive air currents.
According to Sean Carroll at the California Institute of Technology, the EmDrive thrust measured by Eagleworks was due to thermal effect errors. This could provide physicists with some relief seeing that Newton’s and Einstein’s theories remain untainted, although there seems to be some coherence as to whether radiation can be used as a thrust mechanism for space travel.