A Study on Ultra-Low-Pressure Ratio Technology on the Basis of 3D-Printed Propellant for a Solid Rocket Motor

Fused deposition technology (FDM), as an additive manufacturing (AM) technology, holds immense potential in the field of solid grain manufacturing. It can accomplish complex grain shaping with ultra-low-pressure ratios, which are challenging to achieve using conventional grain manufacturing processes. In this work, solid propellants with complex structures were made by using 3D printing. The obtained sample grains of the solid propellants had a complete structure, which conformed to the design model and had no obvious defects. Then, the combustion and mechanical properties of the printed solid propellant were obtained and analyzed. The results show that the composition of the printed solid propellant is more uniform and the performance is better than that of the conventional solid propellant. In addition, by conducting a motor experiment, it was verified that the 3D-printed grains with complex structures have the characteristic of an "ultra-low pressure ratio". The comparative analysis revealed that the maximum working pressure was reduced by about 19.5%, the bearing load of the shell was reduced, and the mass of the shell and other bearing parts was reduced by 11.5%. The research in this paper shows that 3D-printed solid propellant technology can realize the formation of grains with complex structure, which can directly promote the solid rocket motor to obtain the "ultra-low pressure ratio" characteristic, and greatly improve the performance of solid rocket motors.