Screening of metal additives in ABS polymer fuel for enhanced performance in hybrid rocket motors: A computational analysis using CEA

This study investigates the potential of metal additives in acrylonitrile butadiene styrene (ABS) polymer fuel to enhance hybrid rocket motor (HRM) performance through computational analysis, Chemical Equilibrium with Applications (CEA), software. ABS was selected as the base fuel due to its thermoplastic nature, which allows for the creation of complex fuel geometries through 3D printing, offering significant flexibility in fuel design. Hybrid rockets, which combine a solid fuel with a liquid oxidiser, offer advantages in terms of operational simplicity and safety. However, conventional polymer fuels often exhibit low regression rates and suboptimal combustion efficiencies. In this research, we evaluated a range of metal additives—aluminium (Al), boron (B), nickel (Ni), copper (Cu), and iron (Fe)—at chamber pressures ranging from 1 to 30 bar and oxidiser-to-fuel (O/F) ratios between 1.1 and 12, resulting in 1800 unique test conditions. The main performance parameters used to assess each formulation were characteristic velocity (C∗) and adiabatic flame temperature. The results revealed that each test produced a different optimum O/F ratio, with most ratios falling between 4 and 6. The highest performance was achieved at a chamber pressure of 30 bar across all formulations. Among the additives, Al and B demonstrated significant potential for improved combustion performance with increasing metal loadings. In contrast, Fe, Cu, and Ni reached optimal performance at a minimum loading of 1%. Future work includes investigating B-Al metal composites as additives into the ABS base polymer fuel, and doing experimental validation tests where the metallised ABS polymer fuel is 3D printed.