Scientist Chen Wu from the Institute of Mechanics of the Chinese Academy of Sciences offered his explanation of why the EmDrive engine, the principle of which is controversial among experts, does not violate the laws of physics. An explanatory note has been accepted for publication in the peer-reviewed journal Acta Astronautica.
The specialist drew attention to the original explanation of the operation of EmDrive, proposed by the creator of the unit, Briton Roger Scheuer. It takes into account only two vertical forces to calculate the thrust developed by EmDrive, but neglects the influence of forces with horizontal components.
Taking into account the latter, according to Y, allows avoiding the contradiction associated with the seeming violation of the law of conservation of momentum by EmDrive. The contribution unaccounted for by Scheuer in this case is mathematically reduced to the surface integral of the Umov - Poynting vector (the vector of the energy flux density of the electromagnetic field), and physically - to the radiation pressure on the side walls of the EmDrive cavity.
Chen Wu notes that due to its axial symmetry, the horizontal and vertical contributions of previously unaccounted forces on average cancel each other out, however, during short periods of time, on the order of 10 nanoseconds, an imbalance is possible.
Conceptually, the EmDrive consists of a magnetron that generates microwaves and a resonator that stores the energy of their vibrations. Outwardly, the unit resembles a bucket. The design, first proposed in 1999 by Scheuer, allows, he says, to convert radiation into thrust.
In November 2016, a group of NASA scientists published an article about EmDrive in the peer-reviewed journal Journal of Propulsion and Power. It says that the EmDrive in a vacuum develops a thrust of 1.2 millinewtons per kilowatt. The reviewers could not find errors in the design of the test bench and the unit, and the authors of the work - the reverse force that responds to the jet thrust developed by EmDrive, which should be present in accordance with the law of conservation of momentum.
Conservation laws are a consequence of the symmetry properties of space-time. For example, the law of conservation of momentum is a reflection of the homogeneity of space - the equality of its properties regardless of the point chosen in it, and the law of conservation of energy is the homogeneity of time.
