Comparing Hydroxyl Terminated Polybutadiene and Acrylonitrile Butadiene Styrene as Hybrid Rocket Fuels

摘要

Acrylonitrilebutadiene-styrene thermoplastic, widely mass-produced for noncombustion applications including household plumbing and structural materials, is evaluated and compared with hydroxyl-terminated polybutadiene as a potential fuel for hybrid rocket motors. Acrylonitrilebutadiene-styrene has several mechanical properties, including its ability to be fabricated into a wide variety of shapes using fused deposition modeling, which are very attractive as a potential hybrid rocket fuel. The acrylonitrilebutadiene-styrene grains were fabricated using fused deposition modeling from existing rapid-prototyping stock materials composed of 50:43:7 butadiene, acrylonitrile, and styrene mole fractions. The acrylonitrilebutadiene-styrene grains were burned with nitrous oxide as the matching oxidizer and compared for performance and consistency against fuel grains of equal size cast from hydroxyl-terminated polybutadiene and burned with nitrous oxide. Test results demonstrate a higher burn-to-burn consistency for acrylonitrilebutadiene-styrene, but slightly reduced overall performance. Methods for increasing the burn energy of the acrylonitrilebutadiene-styrene fuel grains were investigated. Equilibrium chemistry calculations conclude that, for a given oxidizer-to-fuel ratio, varying the butadiene mole fraction in the acrylonitrilebutadiene-styrene formulation has a significant effect on the propellant performance. A major result of this research is the demonstrated viability of thermoplastic as a hybrid rocket fuel grain material.