Calculation of the unsteady burning velocity according to a known law of pressure variation during transient processes in a solid-propellant rocket engine

The burning velocity during pressure decay in a model solid-propellant engine caused by the opening of an additional nozzle concurrently with the operation of the main nozzle is calculated; i.e., the inverse problem of internal ballistics is solved. The calculations are performed using experimental pressure versus time dependences and the laws of conservation of mass and energy in the thermodynamic and isothermal approximations. The problem is solved in two formulations: using the basic parameters of the combustion chamber before depressurization and in a formulation based on using initial conditions for pressure decay. In the latter case, the unsteady burning velocities are smaller than the corresponding steady-state velocities at the same pressures and close to the calculated velocities obtained for the same pressure decays by solving the direct problem.