Results and experiences from research on ETC

Experiments with the objective to stimulate the combustion of solid propellants through addition of electric energy are reported. The current is conducted through the flame and will supply energy via resistive heating, which adds to the chemical energy release of the flame and thus increases the heat feedback to the unburnt propellant. The electric conductivity of the flame needs to be increased in order to reduce random delay and to increase control of the electric discharge. Thermochemical calculations indicate that substantial increase in conductivity can be obtained by doping the propellants with alkali compounds, provided that the flame temperature is high enough. The experiments are performed in a closed vessel where a propellant slab is pinched between two copper plates connected to a pulsed power supply. The purpose of the present work is to determine whether the alkali doped propellants allow larger currents to be conducted through the reaction zone and if this substantially increases the burn rate. Presented results include comparisons of burn rates for different amounts of electric energy stimulation and for different propellant compositions as well as pressure, voltage and current recordings. The pressure measurements are compared with simulations based on the measured discharged electrical energy.