Abstract—Two manufacturing processes were performed to obtain fuel grains for hybrid rocket engines. Experimental comparisons were made between paraffin grains obtained by traditional casting methods and Acrylonitrile Butadiene Styrene (ABS) grains obtained by Direct-Digital Manufacturing (DDM). The comparative process shows results that present significant advantages between the use of fuels obtained by casting and those obtained by DDM. Features such as dimensional tolerance control, structural strength, presence of cracks and micro combustion chambers are some of the improvements that DDM offers over traditional casting fuel grain manufacturing methods. This characterization was performed on a hybrid rocket engine, designed to inject 99.99% pure nitrous oxide into a combustion chamber with a capacity to withstand 1000 PSI of pressure, and an easy-to-exchange nozzle to avoid erosive behavior in the throat. Parameters such as chamber pressure and engine thrust were measured during the test procedure.