Determining the actual values of specific impulse for the main engines of the block DM upper stages as a routine inverse problem

One of the most important parameters for space launcher vehicles (including Block DM upper stages) to be determined from flight test results is Psp, which is the actual value of the main engine specific impulse. The importance of this parameter lies in the fact that, on the one hand, it is what meeting the upmass performance requirements depends on, and on the other hand, it is one of the main diagnostic parameters of propulsion systems. Traditionally, the most common method for solving such a problem under conditions where direct measurements of this parameter are impossible is the use of the classical Tsiolkovsky formula with inputs from mass-weight analysis. However, experience has shown that this method, due to the low accuracy of such inputs does not provide the required accuracy of the Psp estimates, and in some cases is not applicable at all. This paper shows how the use of some peculiar aspects of the variable-mass mechanics permits to solve such a problem...