Investigation on plasma enhanced decomposition of ammonium dinitramide (ADN) based propellant with optical diagnosis.

Plasma-enhanced decomposition is a promising method to achieve reliable ignition and better thruster performance with an ADN-based propellant. High-speed imaging and optical emission spectroscopy are used to characterize the discharge plasma produced from ADN-based propellant vapor and argon carrier gas within parallel planes. Discharge regimes are independently controlled by varying working parameters. The transition from abnormal glow discharge (AGD) to filamentary discharge (FD) is identified from voltage-current characteristics and sudden changes in excitation electron temperature (T e-exc) and electron density (N e) under a pressure of 0.2–10 kPa. Instabilities develop because there are more freedom degrees and higher collision probabilities after ADN-based propellant vapor is added. The product of T e-exc and N e shows a higher energy transfer efficiency from input power to vapor in the FD regime. Water molecules increase the net dissociative attachment rate and effectively quench N e. Although preheated vapor (as the discharge medium) has a much lower N e , more radicals appear such as OH, NH, CH, CN, N 2 , N 2 +, and C 2 , which promote chemical interactions in an electric field and increase the probability of successful ignition. This can be attributed to thermalization due to an increase in the translational kinetic energy and rotational excitation, which has an important impact on chemical reaction kinetics. Therefore, preheating is verified as critical for improving the ignition and performance of a plasma-assisted ADN-based thruster. [Display omitted] • A discharge plasma can assist ADN-based propellant decomposition. • Abrupt change of plasma parameters indicates discharge regime transition. • Introduce vapor promotes the development of discharge instabilities. • Preheated propellant vapor displays a higher decomposition efficiency. [ABSTRACT FROM AUTHOR]