The ignition and extinction characteristics of perchlorate-based electrically controlled solid propellants (ECSPs) that can achieve multiple ignition and produce controllable thrusts were investigated. We examined the multiple-ignition and combustion behaviors of ECSPs and identified the basic ignition-model parameters for these materials. Single-frame photography and a schlieren imaging system were used to determine the ignition, combustion, and extinction properties of two different ECSP formulations at various voltages, pressures, and initial temperatures. The results revealed that increasing the voltage, pressure, and initial temperature reduced the ignition delay; whereas increasing the number of ignitions decreased the ignition delay and ignition energy but increased the extinction delay and smoldering time. Furthermore, under the same experimental conditions, the voltage, pressure, and initial temperature produced a larger effect on a nonmetallic ECSP than on an ECSP containing 5% aluminum (Al) powder. The nonmetallic ECSP exhibited a longer ignition delay, higher ignition energy, and better extinguishing performance than the Al-containing ECSP. Moreover, four distinct stages of the ECSP ignition process were identified. The findings of this study demonstrated that the electrical energy consumed during condensed phase heating plays a critical role in propellant ignition.

Liquid or gaseous fuel scramjet technology has made great progress, and there has been some research attention to solid-fuel scramjet. A new scramjet configuration using solid fuel as propellant, namely solid-fuel rocket scramjet, is tested experimentally. It consists of two combustors. One is a rocket combustor used as gas generator, and the other is a supersonic combustor used for secondary combustion. The experiment simulates a flight Mach number of 4 at high altitude (stagnation temperature and pressure are 1170 K and 1.16 MPa, respectively), and metalized solid fuel is used as propellant. The results reveal that fuel-rich gas from the gas generator can burn with air in the supersonic combustor. Preliminary evaluation results show that the combustion efficiency of the propellant is about 90%, and the total pressure recovery coefficient in the supersonic combustor is about 0.6. These results indicate that the configuration of solid-fuel rocket scramjet is feasible.

Scramjet based on solid propellant is a good supplement for the power device of future hypersonic vehicles. A new scramjet combustor configuration using solid fuel, namely, the solid fuel rocket scramjet (SFRSCRJ) combustor is proposed. The numerical study was conducted to simulate a flight environment of Mach 6 at a 25 km altitude. Three-dimensional Reynolds-averaged Navier–Stokes equations coupled with shear stress transport (SST) $k-\omega$ turbulence model are used to analyze the effects of the cavity and its position on the combustor. The feasibility of the SFRSCRJ combustor with cavity is demonstrated based on the validation of the numerical method. Results show that the scramjet combustor configuration with a backward-facing step can resist high pressure generated by the combustion in the supersonic combustor. The total combustion efficiency of the SFRSCRJ combustor mainly depends on the combustion of particles in the fuel-rich gas. A proper combustion organization can promote particle combustion and improve the total combustion efficiency. Among the four configurations considered, the combustion efficiency of the mid-cavity configuration is the highest, up to about 70%. Therefore, the cavity can effectively increase the combustion efficiency of the SFRSCRJ combustor.