Multispecies combustion diagnostics using tunable diode laser absorption spectroscopy

Abstract

Multi-species measurements of N2O, CO, NO within an ammonium dinitramide (ADN) based thruster are presented using quantum cascade lasers, while gas temperature are obtained using near-infrared H2O two-line thermometry. ADN monopropellant represents a new generation of green propellant for spacecraft propulsion. Measurements using the developed mid-infrared diagnostic system provide an access to characterize the combustion process inside the ADN based thruster, while theoretical study of ADN monopropellant combustion is still under study. Both steady-state firing and pulse-mode firing for ADN based thruster operation are measured in the present experiments. Results of multispecies concentration agree well with the mechanism of the combustion process and divide the whole process into decomposition stage and combustion stage. Reaction (R1, NH4N( NO2)2→ NH3+N2O+HNO3 ) is the primary reaction branch as N2O generation is much higher and faster than NO generation in decomposition stage at the measured position. To the author’s knowledge, this work represents the first multispecies simultaneous measurements in an actual ADN based thruster using mid-infrared laser absorption spectroscopy. The time-resolved multispecies results aid in an improved understanding of the ADN monopropellant combustion and demonstrate mid infrared diagnostic technique’s practicality for small-sized ADN based thruster.