A new theory about how the EmDrive engine works. The engine is possible otherwise

The famous EmDrive (1) shouldn't break the laws of physics, says Mike McCulloch (2) of the University of Plymouth. The scientist proposes a theory that suggests a new way of understanding the motion and inertia of objects with very small accelerations. If he were right, we would end up calling the mysterious drive "non-inertial", because it is inertia, that is, inertia, that haunts the British researcher.

Inertia is characteristic of all objects that have mass, react to a change in direction or to acceleration. In other words, mass can be thought of as a measure of inertia. Although this seems to us a well-known concept, its very nature is not so obvious. McCulloch's concept is based on the assumption that inertia is due to an effect predicted by general relativity called radiation from Unruhthis is black body radiation acting on accelerating objects. On the other hand, we can say that the temperature of the universe is increasing as we accelerate.

2. Mike McCulloch of Plymouth University

According to McCulloch, inertia is simply the pressure exerted by Unruh radiation on an accelerating body. The effect is difficult to study for the accelerations we commonly observe on Earth. According to the scientist, this becomes visible only when the accelerations become smaller. At very small accelerations, the Unruh wavelengths are so large that they no longer fit into the observable universe. When this happens, McCulloch argues, inertia can only take on certain values ​​and jump from one value to another, which rightly resembles quantum effects. In other words, inertia must be quantized as a component of small accelerations.

McCulloch believes that they can be confirmed by his theory in observations. weird speed spikes observed during the passage of some space objects near the Earth towards other planets. It is difficult to study this effect carefully on Earth because the accelerations associated with it are very small.

As for the EmDrive itself, McCulloch's concept is based on the following idea: if photons have some kind of mass, then when reflected, they must experience inertia. However, the Unruh radiation is very small in this case. So small that it can interact with its immediate environment. In the case of the EmDrive, this is the cone of the "engine" design. The cone allows for Unruh radiation of a certain length at the wider end, and radiation of a shorter length at the narrower end. The photons are reflected, so their inertia in the chamber must change. And from the principle of conservation of momentum, which, contrary to frequent opinions about EmDrive, is not violated in this interpretation, it follows that traction should be created in this way.

McCulloch's theory can be tested experimentally in at least two ways. First, by placing a dielectric inside the chamber - this should increase the efficiency of the drive. Secondly, according to the scientist, changing the size of the chamber can change the direction of thrust. This will happen when the Unruh radiation is better suited to the narrower end of the cone than to the wider one. A similar effect can be caused by changing the frequency of photon beams inside the cone. “Thrust reversal has already happened in a recent NASA experiment,” says the British researcher.

McCulloch's theory, on the one hand, eliminates the problem of conservation of momentum, and on the other hand, is on the sidelines of the scientific mainstream. (typical marginal science). From a scientific point of view, it is debatable to assume that photons have an inertial mass. Moreover, logically, the speed of light should change inside the chamber. This is quite difficult for physicists to accept.

3. The principle of operation of the EmDrive engine

It works but more tests are needed

EmDrive was originally the brainchild of Roger Scheuer, one of the most prominent aeronautical experts in Europe. He presented this design in the form of a conical container. One end of the resonator is wider than the other, and its dimensions are chosen in such a way as to provide resonance for electromagnetic waves of a certain length. As a result, these waves propagating towards the wider end must speed up and slow down towards the narrower end (3). It is assumed that, as a result of different wave front displacement velocities, they exert different radiation pressure on the opposite ends of the resonator, and thus a non-null string that moves the object.

However, according to known physics, if no additional force is applied, momentum cannot increase. Theoretically, EmDrive works using the phenomenon of radiation pressure. The group velocity of an electromagnetic wave, and hence the force generated by it, may depend on the geometry of the waveguide in which it propagates. According to Scheuer's idea, if you build a conical waveguide in such a way that the wave speed at one end differs significantly from the wave speed at the other end, then by reflecting this wave between the two ends, you get a difference in radiation pressure, i.e. sufficient force to achieve traction. According to Shayer, EmDrive does not violate the laws of physics, but uses Einstein's theory - the engine is in a different frame of reference than the "working" wave inside it.

So far, only very small ones have been built. Prototypes of EmDrive with traction force of the order of micronews. A fairly large research institution, China's Xi'an Northwest Polytechnic University, has experimented with a prototype engine with a thrust force of 720 µN (micronewtons). It may not be much, but some ion thrusters used in astronomy don't generate more.

4. EmDrive test 2014.

The version of EmDrive tested by NASA (4) is the work of American designer Guido Fetti. Vacuum testing of the pendulum has confirmed that it achieves a thrust of 30-50 µN. The Eagleworks Laboratory, located at the Lyndon B. Johnson Space Center in Houston, confirmed his work in a vacuum. NASA experts explain the operation of the engine by quantum effects, or rather, by interaction with particles of matter and antimatter that arise and then mutually annihilate in the quantum vacuum.

For a long time, the Americans did not want to officially admit that they observed the thrust produced by EmDrive, fearing that the resulting small value could be due to measurement errors. Therefore, the measurement methods were refined and the experiment was repeated. Only after all this, NASA confirmed the results of the study.

However, as the International Business Times reported in March 2016, one of the NASA employees who worked on the project said that the agency plans to repeat the entire experiment with a separate team. This will allow her to finally test the solution before deciding to invest more money in it.