Shinichi Moriya

Overview of Research and Development Status of Reusable Rocket Engine

This paper reports the status of research and development of a reusable rocket engine in Japan. In the case of an expendable engine, in system selection, much weight must be put on performance, whereas in the case of a reusable engine, in addition to satisfactory performance required by the mission, reusability must be considered. In the system study, total design management (TDM) was employed for the LOx/ethanol engine, and the relation between performance and reusability was quantitatively evaluated. In the research on key components, the combustion chamber, bearings, and seals for turbopumps were selected as key components. To extend the lifetime of the combustion chamber, lowering the wall temperature is important, and thermal barrier coating (TBC) or film cooling (FC) becomes necessary. Turbopumps with a port for installation of a fiberscope on the bearing’s inner ring and on the shaft seal’s nose for direct observation were developed, and the feasibility of 100 reuses was established. A demonstration engine of the reusable sounding rocket was manufactured, and more than 100 operation cycle tests were carried out to confirm the feasibility of 100 reuses. Durability was confirmed by lifetime audit testing.

Feasibility study on a neutron diffraction method for non-destructive evaluation of residual strain distribution of a combustion chamber

A regeneratively cooled combustion chamber of a cryogenic liquid rocket engine is exposed to a large temperature difference between a combustion gas and a liquid hydrogen coolant. The large temperature difference induces large thermal stress in the chamber wall, and the strain is accumulated throughout the cyclic firing tests. Evaluation of the stress and the strain distribution in a chamber wall is essential for chamber life prediction because the chamber life is related to such stress and strain. A feasibility study on a neutron diffraction method for evaluation of residual strain distribution in a chamber wall was conducted. A method of positioning cooling channels inside a combustion chamber was established. The measurement time was adjusted to improve the fluctuation of the diffraction data. The measured data were compared with the numerical data by finite element analysis.

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.