Keiichi Hasegawa

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.

Dynamic Characteristics of an Extendible Nozzle during Deployment

*† ‡ § ** †† 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 engines with the extendible nozzle have to deploy the extendible nozzle during firing. For the design of the extendible nozzle and its driving mechanics, it is required to clarify the dynamic characteristics of the extendible nozzle. Dynamic characteristics of the loads acting on the extendible nozzle were investigated through the firing tests on a high altitude test stand with varying the ambient pressure to simulate the altitude change. In the firing tests, the extendible nozzle supported by four or six rods was used. The thrust and side loads acting on the extendible nozzle were evaluated quantitatively by using the supporting system consisted of six rods. Using the measured load data and the calculated nozzle pressure distribution data, the estimation of flow separation point were carried out. The effect of deployment position was also clarified.

Combustion Gas Heating Tests of C/C Composites Coated with SiC Layer

In order to examine the applicability of carbon fiber/carbon matrix composites coated with a silicon carbide layer (C/C‐SiCs) to an advanced nozzle for the future reusable rocket engines, two series of combustion gas heating tests were conducted using a small rocket combustor. In the first series of heating tests, five different kinds of C/C‐SiCs were tested with specimens in the shape of a square plate for material screening. In the second series of heating tests, two selected C/C‐SiCs were tested with specimens in the shape of a small nozzle. The effectiveness of an interlayer between a C/C composite and a SiC layer, which was introduced to improve the durability based on the concept of functionally graded materials (FGMs), can be observed. The typical damage mode was also pointed out in the results of heating test using the small nozzle specimens.