Simulation of plasma radiation in electrothermal-chemical accelerators

The energy transport by radiation in hot, dense plasmas - as produced in the temperature/density range of electrothermal-chemical (ETC) guns - is the dominant effect in the energy balance. For this reason, radiation is an important factor in the initiation, control and optimization of the ignition and combustion processes of propellant charges by a plasma in such devices. Results of published experiments also indicate a strong interaction between the plasma radiation and the surrounding propellant and combustion products. For the optimization of ETC guns a program has been developed using the approximate method of "partial characteristics" for the solution of the radiative transfer equation (RTE) under the assumption of local thermodynamic equilibrium (LTE). The computation of the RTE depends on frequency dependent absorption, emission and scattering coefficients, which describe the interaction of the radiation field with matter. Therefore, the IABG has developed the program FOCAL which calculates absorption, emission and scattering coefficients for molecular bands, atomic and ionic lines as well as continuum radiation using a model of detailed configuration accounting. Having computed the radiation transport, this solution may then be used in the conservation equations III and to establish the direct transfer of radiative flux to the surrounding propellant charges.