A new reaction system that uses discharge plasma of noble gas has been proposed as a substitute for the conventional solid catalyst in a reaction control system (RCS) thruster. The propellant of the thruster is a hydroxyl ammonium nitrate (HAN)-based monopropellant instead of the usual hydrazine. The proposed reaction system is a discharge plasma catalyzer (DPC) system, and a laboratory model (LM) has been developed. The DPC-LM is expected to enhance combustion via ion-molecule and

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... ule reactions from the discharge plasma, and to enable cold-start operation. The objective of this study is to experimentally evaluate the effects of characteristics of the discharge plasma on the propellant reaction characteristics of the DPC-LM by inducing different swirl gas flow patterns, such as by varying the geometric swirl number. The plasma characteristics are evaluated in terms of the success rate of propellant reaction and the reaction delay time. The continuity of the exhaust flame was confirmed for argon gas mass flow rates from 0.125 to 0.175 g/s and an SHP163 mass flow rate of 0.3 g/s with higher geometric swirl numbers. In addition, it was found that higher geometric swirl numbers reduced the reaction delay time.