Current distribution and resistance characteristics in plasma injectors for electrothermal-chemical launch

A two-dimensional model is developed for investigating electrical conduction in plasma injectors that consist of a periodic array of solid and plasma conductors. The model studied is general but the basic analysis applies to a variety of devices and experimental situations. Calculations are undertaken to determine the preferred conduction pathways as well as the impedance in such an injector as a function of several relevant parameters. These parameters include the relative dimensions of the solid and the aspect ratio of the conduction domain. It is shown that under some conditions the current will flow predominantly in the plasma and bypass the low-resistance path provided by the solid. Such an event is undesirable for several reasons discussed, and methods for preventing its occurrence are suggested. Additional calculations include the resistance of the injector and the fractional amount of current that flows through the solid. These quantities are shown to depend on the various length scales pertinent to the problem