後藤 健

A nitrous oxide (N₂O) / ethanol propulsion system has been studying in ISAS/JAXA since 2003. The propellant combination can be characterized as a bi-propellant with extremely low toxicity, room temperature storability, low freezing point, and high energy density, which is applicable to spacecraft propulsion systems. So far, seven series of captive firing tests including high altitude tests were performed with a breadboard model (BBM) of 2 kN thrust class propulsion system which was built for evaluating its propulsive performance and system operability. In these tests, the capabilities of prototype of a like-doublet impingement injector and the durability of a combustion chamber made of a heat resistant fiber-reinforced ceramic composite (SiC/SiC) were evaluated. From the viewpoint of the engine system design, a relationship between the wall heat flux determined with the water cooling combustion chamber and the propellant mixture ratio was examined from the test results. Findings and issues to be associated with the injector design and the engine operation were also obtained in the present study. This paper presents an overview of the achievements of the technology demonstrations with the BBM.