To replace hydrazine, a deadly toxic monopropellant for RCS (Reaction control system), research on green propellants has been vitalized, and green propellants based on HAN (Hydroxyl Ammonium Nitrate) or ADN (Ammonium Dinitramide) are promising candidates. Because an improvement in combustion characteristics is required to achieve the practical use of green propellants, we focused on the atomization of green propellants. Viscosity and surface tension measurements and injection tests under the condition assuming 1-10 N class RCS were conducted to inspect the atomization characteristics of green propellant candidates. The results revealed a clear highly viscous trend of the candidate materials and the difficulty of atomization by the swirl injector. These results indicate the importance of viscosity reduction in the atomization of green propellants.

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