Study on combustion instability of solid rocket motor with finocyl grain

Combustion instability or oscillation combustion which occurs in three high loading fraction solid rocket motors using high energy composite propellant with finocyl grain was discussed. Spectrum analysis result indicates that the combustion instability in all the three motors mentioned above occurs in longitudinal medium frequency. The reasons of the acoustic combustion instability were also discussed. Whether the pressure oscillation will continue to grow or not depends on the design of the grain and the final result of amplifying or dampening to each type of oscillations in the chamber. The basic ways to prevent this kind of combustion instability are modification of the grain geometry in the combustion chamber and also the nozzle structure to increase nozzle damping effect. Static test results of the redesigned rocket motors indicate that the proposed methods can significantly eliminate the combustion instability and improve the motor internal ballistic performance.