| dc.description.abstract | Within identical composite solid AP/HTPB propellant formulations, the densities of each individual propellant can greatly vary depending on their manufacturing quality. Propellants with lower densities than their theoretical maximum densities usually indicate the presence of air bubbles, or voids, within the propellant structure. The effects of these voids on the burning rates of propellants were investigated and thoroughly characterized by comparing the manufacturing quality and performance of propellants with differing densities. Baseline AP/HTPB propellants were manufactured using a custom designed extruder that can produce high density propellants. This custom extruder can also be modified to create low density propellants by deliberately introducing air into the system to induce the formation of voids. A burning rate curve for low-, medium-, and high-density propellants was developed for a pressure range between 500 and 2500 psia. These results indicate that low-density propellants will have measurably higher burning rates than high-density propellants. Numerous propellants were also repeatedly tested for burning rates at 500 and at 3000 psia to determine how the scatter and deviation of burning rates are affected by propellant density at both low and high pressures. These results indicate that low-density propellants will display a higher burning rate variance compared to high-density propellants. In addition, the low-density propellants were shown to have statistically significant different burning rates compared to the high-density propellants at low pressures. This study demonstrates that voids in propellant can greatly impact the performance and safety of a rocket motor. | |
