Rapid Prototyping of polymers has evolved to the point where it can be applied to fabricate hybrid rocket fuel grains. Intricate grain designs with complex port geometry can be made with increased surface area and with no additional machining cost. Several samples of either printed pure acrylic, printed heterogeneous paraffin/acrylic matrix, or cast paraffin grains were provided by collaborators at the Aerospace Corporation and have been tested in the Long Grain Center Perforated (LGCP) hybrid rocket motor at the Pennsylvania State University’s High Pressure Combustion Laboratory (HPCL). These solid fuel grains exhibit either a star-swirl or protruding vane turbulator center port design. Due to the complexity of these shapes, post-burn regression analysis for star-swirl type geometry was performed using SolidWorks CAD software to match a computer model to the actual burn profile. Regression rate increases of over 270% were noted in1/2-tpi star-swirl acrylic samples. Cast paraffin containing 20% aluminum with a printed1/4-tpi turbulator insert has been shown to increase regression rate by over 70% and demonstrates the ability to incorporate energetic additives while still applying swirl-inducing geometry. An oxidizer swirl injector system for the LGCP hybrid rocket motor has been designed and fabricated; the 45-degree injector head provided over 180 % increase in regression rate for straight-port cast paraffin fuel grains in comparison to straight-port axial injection. Using the same swirl injector configuration with straight-port printed paraffin/acrylic samples provides minimal improvement, likely due to the flow-straightening effect and boundary layer disruption of the acrylic support material. Overall, these tests provide a better understanding of the capabilities of rapid prototyping for application to future hybrid fuel grains. They also demonstrate the potential of hybrid rockets for small-scale thrusters by overcoming some of the limitations associated with solid-fuel regression rate.