Enhancement of Volumetric Specific Impulse in HTPB/Ammonium Nitrate Mixed Hybrid Rocket Systems

Enhancement of Volumetric Specific Impulse in HTPB/Ammonium Nitrate Mixed Hybrid Rocket Systems by Jacob W. Forsyth, Master of Science Utah State University, 2016 Major Professor: Dr. Stephen A. Whitmore Department: Mechanical and Aerospace Engineering Hybrid rocket systems are safer and have higher specific impulse than solid rockets. However, due to large oxidizer tanks and low regression rates, hybrid rockets have low volumetric efficiency and very long longitudinal profiles, which limit many of the applications for which hybrids can be used. This research investigates a method for increasing the volumetric efficiency and improving the form factor of hybrid rocket systems by a non-combustible load of solid oxidizer to the hybrid fuel grain. Including such oxidizers increases the regression rate of the fuel and lowers the amount of fluid oxidizer needed for optimal combustion. This type of solution is referred to as a “mixed hybrid”. Ammonium perchlorate is often the oxidizer of choice for these applications. However, ammonium perchlorate is extremely dangerous to work with and is an environmental pollutant. This study suggests the use of ammonium nitrate in place of ammonium perchlorate as a more environmentally friendly, lower risk oxidizer in mixed hybrid rocket systems. Presented results quantify the effects of ammonium nitrate in lab scale tests. Further research paths for ammonium nitrate mixed hybrids are outlined.