Kazuo Kusaka

Development status of the reusable high-performance engines with functionally graded materials ☆

Abstract The background of the development of the two kinds of reusable high-performance engine is described. One of these two is the regeneratively cooled 1200 N thrust engine composed of two kinds of ZrO2/Ni functionally graded materials (FGMs) chambers. This engine is a promising candidate for the future Japanese orbiting maneuvering system (OMS) engine of the H-II orbiting plane (HOPE). The other one is the reaction control system (RCS) engine which may also be used compatibly with HOPE. Developed RCS chambers are made of carbon-fiber-reinforced carbon matrix (C/C) composites coated with SiC FGMs. In the first stage of the development of the ZrO2/Ni FGMs chamber, durability tests using a ZrO2 (24.5 vol%)/Ni (75.5 vol%) FGMs chamber were performed to inspect the damage of the thermal coating layer and to evaluate the engine performance after a total of 260 firing tests. In the second stage, a combustion chamber having a compositional profile of perfect ZrO2/Ni FGMs was used in the high-altitude performance tests (HAPT). Firing tests for the C/C–SiC FGMs chamber developed in the first stage were performed at sea level. In this test series, microcracks and penetration of the combustion gases were observed especially at the surface of the nozzle throat section after 382 cycle tests. In the next stage of developing C/C–SiC FGMs chamber (expansion area ratio of 30:1), it was shown that coating with FGMs seemed to effectively prevent the delamination of the SiC coating after 693 cycles under the conditions of P c =1.0 MPa , MR=1.65 and with an injector film cooling rate of 17%, over a total firing time of 2000 s .

Characteristics of Dynamic Loads Acting on an Extendible Nozzle

An extendible nozzle is considered to be a feasible device to improve the performance of booster engines because it has possibilities to provide altitude compensation and to achieve higher specific impulse. The booster engine with the extendible nozzle has to deploy its extendible nozzle during firing. The loads acting on the extendible nozzle vary with a nozzle deployment position as well as an altitude. For the design of the extendible nozzle and its driving mechanics, it is required to clarify the characteristics of dynamic loads acting on the extendible nozzle. In order to investigate the characteristics of dynamic loads, firing tests were carried out on a high altitude test stand. The extendible nozzle was sustained by a nozzle supporting system composed of six rods, and the nozzle deploying position was adjusted at 100%, 76%, and 56% deployed position. In the firing tests, the ambient pressure was varied to simulate an altitude change. The axial load and side load acting on the extendible nozzle were evaluated quantitatively by using small load cells installed in each supporting rod. From the experimental data of dynamic loads acting on the extendible nozzle for 100%, 76%, and 56% deployed position, the effect of nozzle deployment position on the dynamic loads were clarified.