According to classical mechanics, as a consequence of Newton's three laws, the momentum of two (or more) bodies in a closed inertial system, regardless of the interactions between the bodies, is always equal to zero. Thus, the center of mass of the closed system (regardless of the interactions between the bodies) remains at rest or maintains its inertial motion, i.e., the law of conservation of the motion of the center of mass of a closed system is valid. Which is an experimental fact described by Newton in „The Mathematical Principles of Natural Philosophy“ [1], see Corollary 3 and Corollary 4 on pages 420 and 421. Therefore, propulsion of a spacecraft in outer space can be achieved by means of a reaction engine and the application of Newton's third law, as the propellant escaping through the nozzle under pressure creates thrust in the opposite direction of the exiting gases, in accordance with the law: For every action, there is an equal and opposite reaction.. Thus, spacecraft propulsion is associated with a constant propellant expenditure, making them inefficient in terms of propellant usage. The problem is that propellant intended for later use must be factored in as payload on the spacecraft, which is accelerated every time along with the actual payload, and is used only once during a specific period of the space mission.
This book examines a special case of the law of conservation of momentum of the center of mass of a closed inertial system – a two-body device – TBD (two hulls). As in this special case, we get an uncompensated impulse – UCM for one of the device's casings. The conditionally designated first casing is a standard classical body. While the second casing consists of two disks of equal mass, attached to the second casing, but in such a way that they can rotate freely relative to it. And when Newton's third law is applied between the two casings, the inertia of the two disks (which rotate in opposite directions) is used. In this way, since kinetic energy is an additive quantity, the casing with the disks distributes its energy for the rotational movements of the disks and for the translational motion of the second casing. (See ANIMATION-1 [7], where the processes under consideration are clearly shown.)
