System for measuring side thrust forces in small solid propellant rocket motors

A system for measuring the side forces occurring at the exhaust plane of solid propellant rocket motors is described. These forces arise from the misalignment of the thrust vector in the motor. The system measures the following forces: the axial thrust and four components of the side thrust. The system was designed to be free of any moments. A computer program was written to compute accurately the forces, by the method of interpolation over small regions, assuming linearity there. Four types of solid propellant rocket motors were tested by static firing. Good accuracy was obtained by the combined use of the system, an appropriate calibration procedure, and adequate software.