Technical approach to evaluating the loss in rocket motor specific impulse due to discontinuity of the nozzle block contour

A methodical approach to evaluating the loss in rocket motor specific impulse due to discontinuity of the contour of the supersonic part of the nozzle block is developed based on calculating the parameters of the nonisentropic flow of combustion products. The increase in entropy is a consequence of flow deflection and the occurrence of oblique shocks in the zone of contour junction. The magnitude of the loss is determined by the energy expended in increasing the entropy when the flow passes through a shock and is obtained using the equation of the Hugoniot adiabat. The loss in specific impulse was calculated for various discontinuity parameters of the nozzle contour of a hypothetical solid rocket motor.