Abstract
The Holloman Air Force Base High Speed Test Track is in need of a new rocket to replace the aging fleet of rockets currently being used on the facility’s test sleds. These rockets are reaching the end of their shelf lives and the base is looking for greater safety, functionality, storability, manufacturability, and cost effectiveness in their next rocket. Due to the unique application a non-vertical configuration, research has shown that a hybrid rocket is better suited to meet the requirements than a solid or liquid rocket. Hybrid rockets offer a unique advantage in reusability with replaceable solid fuel grains and refillable oxidizer tanks. Because each rocket will be recovered with its associated test sled and article, a reusable rocket is ideal for cutting costs. The prototype delivered must have a rapid initial acceleration with a long sustained thrust on the order of 20,000-30,000 pounds. Unique fuel grain geometries and viable fuels were researched and validated by internal ballistics modeling software, yielding multiple thrust curves that met the thrust requirements. The geometries analyzed included wagon wheel, rod-and-tube, star, and double anchor. The fuels analyzed included polymethylmethacrylate (PMMA), acrylonitrile butadiene styrene (ABS), hydroxyl-terminated polybutadiene (HTPB), and paraffin wax. A rod-and-tube or star shape were determined to be the most appropriate grain geometries and the most viable fuels were found to be 3-D printed ABS or molded HTPB. Tests involving an in-house manufactured thrust stand are expected to confirm comparable thrust between ABS and HTPB, as well as a near-neutral thrust curve for a star geometry and an even more neutral thrust curve for a rod-and-tube geometry. These tests will indicate the ideal fuel and grain geometry to select, from which two fully-integrated scalable prototypes will be built and tested, while a third full size and reusable prototype will be delivered and tested at the Holloman High Speed Test Track.