Evaluation of granular distribution and propellant grain length on tri-modal ammonium perchlorate solid rocket motors
Abstract
This paper presents an evaluation on the effects that variances in ammonium perchlorate particles size, total aluminum content ratio, and solid rocket motor geometry has on tri-modal ammonium perchlorate composite solid propellant (APCP) performance. The primary goal of this study is to observe variances in consistency of solid motor performance as a function of average ammonium perchlorate particle size, differing formulation ratios of fuel and oxidizer, and number of propellant grains present within the motor. Despite ammonium perchlorate’s wide usage in civil and defense applications, its chemical thermal decomposition is largely not well understood. Additionally, once propellant grains have been cast, the only readily available and non-invasive way to quality check a motor is through comparison of theoretical and actual densities. Quality checks give an indication for the amount of imperfections that cause unpredictable variations in performance metrics related to thrust, burn time, and impulse. A stochastic study to characterize performance fluctuations related to the manufacturing of APCP was conducted. Performance variations were evaluated on a 54 mm diameter motor over three different combinations of 90 µm, 200 µm, and 400 µm ammonium perchlorate particle sizes with respect to 2 and 3 grain motor configurations. Variances in aluminum content were evaluated at an average ammonium perchlorate particle size of 261 µm in a 2 grain configuration. Small sample hypothesis variance testing of motor performance at a 90% confidence level suggests that 2 grain motor configurations and increased aluminum content significantly decreased variations in several motor performance parameters. Variations in ammonium perchlorate average particle sizes showed that fluctuations in performance parameters of peak thrust, average thrust, and burn time reduced at an average particle size of 230 µm. However, average particle sizes of 261 µm and 199 µm supported increased consistency with respect to total and specific impulse. Ensemble analysis supports the conclusions from hypothesis testing as thrust profiles at higher aluminum contents, 2 grain motor configurations, and 230 µm ammonium perchlorate average particle sizes exhibited less average deviations and increased thrust profile consistency.
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- OSU Theses [15752]