As dwindling federal funding continues to constrict the national space program, private entities have carried the torch of innovation in the aerospace industry. While the concept of hybrid rocket engines, systems where solid fuels and fluid oxidizers are used for combustion, was conceived during the mid-20th century, the aerospace industry only recently has substantially increased research and development of these engines. According to the literature, hybrids are safer and cheaper than their liquid counterparts due to the utilization of solid fuel and generally provide greater values of specific impulse, density specific impulse, and fuel energy density than traditional solid-fuel engines. This paper provides an overview of the design principles used to develop hybrid engines and discusses limitations currently faced by industry. Furthermore, development of hybrid engines to allow for both scalability and reusability are explored as private aerospace companies continue to demonstrate that reusable rockets are the future of rocket technology. With applications catering from low-payload cargo delivery to the increasing interest in space tourism and exploration, hybrid engines can provide a safer, less expensive solution than traditional and well-established engine selections. Suggestions for future design opportunities and methods are proposed and discussed to make the concept of hybrid engines a viable innovation in the future of rocketry.
Design, Production and Evaluation of 3D-Printed Mold Geometries for a Hybrid Rocket Engine