Analysis of 3-D Braided Composite Ablative Rocket Nozzle

Aerodynamic flow, thermal flow, and stress analyses of a proposed 2.5-in braided composite ablative nozzle were conducted. The nozzle was made up of PAN based carbon fiber and Primaset Cyanate Ester resin. The designed thermal and structural layers’ thicknesses were 0.62-in and 0.42-in, respectively. The objective of this paper is to establish the thermal stability and structural integrity of the nozzle. A ballistic profile of 17 seconds burn at 740 psi maximum pressure was used in the analysis. The combustion gas flow was subsonic, sonic, and supersonic, respectively, in the inlet, throat, and exit sections of the nozzle. The exit plane Mach number was 2.32. Three thermochemical states were considered: 100% efficiency, 72% efficiency and no aluminum combustion and 72% efficiency and 100% aluminum combustion. Flow analysis was conducted by NAT92 Code, thermal analysis by CMAFLOW92 Code, and structural analysis by ANSYS. Ablation rates for the three cases were 0.023, 0.047, and 0.01-in/sec, respectively. The recession life of thermal layer was 27, 13, and 62 sec for the three cases. Stress analysis of the nozzle due to aerodynamic pressure and temperature resulted in low strains and presents no concern.