Development of a Three-Dimensional Printed, Liquid-Cooled Nozzle for a Hybrid Rocket Motor

Additive manufacturing, or three-dimensional (3-D) printing, has rapidly changed from a means to produce component prototypes into a viable method of manufacturing complex, functional parts or devices. It is anticipated that any portions of the inner wall that exceed the temperature limits of the material will melt away, thereby reducing the wall thickness to a steady-state value that depends on the local heating rate, with thinner walls resulting from higher heating rates. Obviously, this process is self-limited, because once the walls become too thin, they will fail due to either hoop or shear stress. Coolant flow begins several seconds prior to combustion to avoid nozzle damage. The chamber pressure and thrust begin to rise before airflow is initiated due to the use of propane and oxygen to start the combustion process.