Equations of Motion of a Space Body at a Variable Velocity of Discharging Combustion Products in the Prerequisites of the Special Theory of Relativity

A controlled (variable) rate of mass discharge generated by the mechanism of using the internal energy is postulated for a space body with variable composition. Based on this postulate, equations of the dynamics without external forces are derived within the special theory of relativity, the solution of which makes it possible to study crucial rocket dynamics and astrophysics problems over the entire physical range of speeds of motion.