Rocket plume electron density measurements through microwave transmissions

The affinity of lightning to a charged rocket plume depends on the plume´s electrical properties, many of which are poorly characterized in theoretical models. The vulnerability of rockets to lightning-induced vehicle failure motivates study of this phenomenon. This paper describes experimental efforts to determine the plasma frequency and electron number density of plumes from static firings of amateur high power rocket motors, by analysis of the microwave transmission characteristics. Two new techniques presented include time delay measurements and using reflectors to sample multiple paths in the plume.