Feasibility study and thermal behavior analysis of rocket nozzle using UHTC-based refractory material

Abstract

In a rocket system, a material exposed to an extremely high-temperature environment. Existing materials such as metal, pyrolytic composite and graphite suffer from ablation. The ablation problem causes enlargement of nozzle throat during operation. As the nozzle enlarges, the combustion pressure drops significantly. Hence, long-term combustion is a challenging problem for the rocket system without proper cooling. In this study, the refractoriness of the rocket nozzle was raised by implementing Ultra-High Temperature Ceramics (UHTCs). The UHTC has a high melting point of above 2,000℃ and superior oxidation/ablation resistance. Unlike the existing material, UHTC forms the refractory oxide layer when the material oxidized. This self-generating oxide layer of UHTC protects the structural materials by hampering oxidizing-compound to diffuse into the base material. In this study, to test the feasibility of applying UHTC into rocket nozzle, 250N scale %H_2O_2$/HDPE hybrid thruster was designed. The long-term hot fire tests were conducted to test the ablation characteristics of HfC-SiC and $HfB_2$-SiC nozzle insert. The UHTC insert showed near zero erosion on the nozzle throat compare to graphite nozzle which presented substantial ablation. The combustion parameter such as chamber pressure and thermal behavior of UHTC were profoundly analyzed. Based on the analysis, the feasibility of UHTC application into the rocket nozzle evaluated.