Controllable ignition, combustion and extinguishment characteristics of HAN-based solid propellant stimulated by electric energy

Hydroxyl ammonium nitrate (HAN)-based electrically controlled solid propellant (ECSP) is the advanced solid chemical propellant stimulated by electric energy, which has throttleable ability. This characteristic is impossible for traditional solid propellants, and greatly expands the potential applications for solid rocket motors that are fit with the ECSP. In this work, the ignition, combustion and extinguishment characteristics of propellant were studied at different voltages, initial temperatures and pressures. It is concluded that the incremental voltage, initial temperature and pressure enhance the burning rate, mass loss and extinguishment delay time, while reducing the ignition delay time, energy required for ignition and electrolysis mass ratio. Specially, as the initial temperature increases from -15 °C to 45 °C (at 200 V and 0.1 MPa), values of mean ignition delay time decrease from 247.4 ms to 116.2 ms, and values of mean burning rate and extinguishment delay time increase from 0.25 mm/s to 0.47 mm/s and 19.2 ms to 27.6 ms, respectively. Moreover, as the pressure increases from 0.1 MPa to 1.0 MPa (at 200 V and 25 °C), values of mean ignition delay time decrease from 151.6 ms to 74.2 ms, and values of mean burning rate and extinguishment delay time increase from 0.44 mm/s to 0.89 mm/s and 28.0 ms to 55.6 ms, respectively. Based on the experimental results, the processes of propellant from ignition to extinguishment were analyzed, and the ignition mechanism was proposed that the fracture of NOH in NH3OH+ in the electrochemical decomposition is a key step that affects the ignition of ECSP. Overall, those results reveal that the electrolysis reaction rather than the pyrolysis reaction exerts an important role for ECSP on achieving the controllable combustion.