Load resistance estimation in ETC experiments

The performance of electrothermal-chemical (ETC) guns, besides being dependent on the total energy used, is also influenced by the time frame over which electric energy is deposited. This means the current pulse shaping is an important factor in increasing the pressure pulsewidth within the limit of the gun design pressure. For experiment design, it is necessary to predict the load resistance to supply the required shape of current pulses into the gun load. But it is difficult to identify the load resistance theoretically because the dynamic interactions of plasma with propellants should be understood. In this paper, it is suggested that the measured current and voltage can be utilized to develop an approximated model of the load resistance. It is also shown that the load resistance depends on the discharging voltage and current. Experimental tests have been performed with several shapes of current pulses to validate the resistance model.