Recent experimental and theoretical research efforts have focused on the use of plasma to optimize and control solid propellant ignition and combustion processes in an energetic fluid bed. However, prediction of electrothermal plasmas in terms of temperature, velocity and density distributions have been difficult. We present here a two-phase flow model for flame-spreading and spatial variation in solid propellant ignition and combustion processes. An integral-numerical method is used to describe the plasma jet penetration for the early part of the combustion process. A mixing length model with an electrical enhancement factor of the burning rate is used for the major combustion cycle. The model plasma jet results agree with the gross features of those determined experimentally.