Abstract
Hybrid rocket engines provide many advantages over current solid and liquid systems including: throttling capability, good specific impulse, and relatively low cost due to greater operational safety and simplicity. However, hybrid rockets are limited by low fuel regression rates and combustion efficiencies. In recent years, additive manufacturing (AM) has been implemented in the design, print, and testing of hybrid rocket fuels. AM has enabled design of fuel grains with complex port geometries which are not possible or difficult to achieve through conventional casting techniques. These geometries can be used to manipulate the oxidizer flow and fuel interactions to increase performance of the engine. Recent studies using a variety of performance enhancing geometries have shown significant regression rate increases. Although recent developments in additive manufacturing of hybrid fuels are promising, there are many geometries and configurations that remain unexplored. Additional testing is required to fully understand the performance enhancing mechanisms, demonstrate reliability, and explore potential new geometries. In this study, work has been performed in gaining a fundamental understanding of hybrid rocket theory and developing fuel printing and testing capability. A thrust stand was developed at the University of Miami to conduct hot-fire experiments of printed fuels. Preliminary tests conducted at UM with ABS fuel grains and gaseous oxygen show baseline performance similar to previously published data. A process was also developed to additively manufacture and test a 3D printed compound ABS+Aluminum complex port fuel grain, resulting in the first known successful test of such a fuel grain.