Influence of pintle ablation on internal ballistics of variable thrust solid motor

To investigate the internal ballistics characteristics of the variable thrust solid motor during the operation process with pintle ablation, a variable thrust solid rocket motor with rear-mounted pintle was designed in this paper, and the hot firing test of the motor was carried out. The test results show that the pintle ablation was severe near the throat, with a maximum average radial ablation rate of 1.31 mm/s. An internal ballistic model considering pintle ablation was established, and the calculation results were in good agreement with the experimental data. Compared with the model without considering pintle ablation, the maximum deviation of the calculation results was reduced from 12.9% to less than 3%. The pintle ablation led to a significant reduction in the regulating capacity of the motor, and the pressure regulating range decreased by 43.4%. The influences of the onset time and the rate of ablation on the internal ballistics were studied. It was found that the delay of the onset time of pintle ablation can cause the pressure change rate and the pressure peak in the pressure boosting section to increase first and then remain unchanged, while the pressure change rate in the pressure reduction section and the pressure fluctuation in the platform section to increase first and then decrease. With the increase of the ablation rate, the pressure change rate and the pressure peak in the pressure rising and dropping sections decreased, the pressure change rate in the pressure reduction section gradually decreased to zero, the pressure fluctuation in the platform section increased first and then decreased, and the pressure deviation monotonically increased and then tended to a constant value.