I. Introduction nternal ballistics analysis, especially prediction of pressure and thrust time history of solid rocket motor (SRM) is one of the most important parts of rocket design. Usually, the spin is used to increase the directional stability of SRMs. The angular velocity of the rocket changes the internal ballistics of the motor and increases the operating pressure and decreases the burning time due to burning rate increment. This pressure increment is a function of many parameters. the most important ones are grain shape, rocket size and its angular velocity. As shown in experimental firing data, motors with internal burning cylindrical grain are more sensitive to spin than other configurations. 1 Since these effects are important from different design aspects including structural mechanics and flight dynamics, therefore the internal ballistics of spinning solid rocket motor needs to be analyzed accurately to make the design process credible enough.

Many studies have been done to analyze the physical effects of normal acceleration on the burning rate of solid propellant that had helped to develop the regression rate models for propellant under acceleration influence. 2-6 It has been found that the burning rate of both aluminized and nonaluminized propellants are dependent to the acceleration which is a function of base burning rate, aluminum mass loading and particles size and acceleration level. Also, the relative burning rate increase was found to be greater for slow burning propellants than for faster burning propellants. 7 Flight tests show that the longitudinal acceleration reduces the spin acceleration effects. 8 It has been shown that the overall burning rate depends strongly on the angle of acceleration vector with respect to the burning