Hybrid Rocket Studies Using HTPB/Paraffin Fuel Blends in Gaseous Oxygen Flow

Hybrid rockets have superior safety, versatility, and reliability over solid or liquid propellant rockets. However, low solid fuel regression rates and corresponding low thrust have hindered their application and utilization. Paraffin fuels regress significantly faster than traditional polymeric fuels, such as HTPB, and paraffin inclusion in HTPB represents a potential tool for performance augmentation in hybrid rockets. A comprehensive literature survey regarding mixed HTPB/paraffin fuels for hybrid rocket applications is presented herein. Plain HTPB; plain paraffin; and HTPB loaded with 10, 25, 50, and 75% paraffin fuel specimens were manufactured by inclusion of molten paraffin at elevated temperatures. The prepared fuel grains were burned in gaseous oxygen on a lab-scale hybrid rocket at moderate oxidizer mass fluxes (7-130 kg/m2 s) and low pressures (0.2-0.9 MPa). Plain paraffin fuel exhibited a 300% increase in regression rate over plain HTPB. However, none of the mixed fuel formulations exhibited notable regression rate enhancement at the evaluated operating conditions.

Hybrid Rocket Studies Using HTPB/Paraffin Fuel Blends in Gaseous Oxygen Flow Conference Paper