HAN-based liquid monopropellant is considered as promising alternative for hydrazine toxic system due to its high specific impulse, high density and low freezing point. During the application for HAN thrusters for reaction control system and green spacecraft subsystem, storage stability for long service life on orbit is one of the important problems for HAN monopropellant by the presence of metal ions such as Fe~(3+). Moreover, tests of material compatibility showed that some amount of metal ions elute from the surface of fuel tank and tubes. Therefore, the control of Fe~(3+) metal ions is required for propellants stability. The possible red-ox reactions between HAN and metal ions were demonstrated. To resolve this problem, tree chelating agents of Fe~(3+) ions were selected and added to different solutions of HAN 93 % mixed with Fe~(3+) ions in order to uptake the maximum of present ions. The solutions were controlled by DTA-TG before and after addition of chelating agents. The burning rates were also calculated from combustion of those solutions before and after addition of chelating agents. Chelating agents can be considered as promising additives to minimize the effect of Fe~(3+) ions, and the ability of iron species chelating of different agents was strongly depended on the initial concentration of HAN solutions.
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