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In this paper, a multiphysics numerical approach for predicting the ionization level in solid rocket engine plumes is presented. Ionization takes place in the rocket combustion chamber and in the exhaust plume. A low-temperature, high-density plasma is created, with small Debye length in most of the plume region. Ambipolar diffusion is therefore assumed for ions and electrons in the plume, and a set of conservation equations is derived to be solved by the numerical model. A number of numerical strategies to resolve this system is derived, as well as a novel scheme that enforces charge neutrality. This approach is integrated into a complex code for compressible, multispecies, turbulent flow simulations. The model is then coupled with a Maxwell's equations solver in order to simulate the radar cross section of rocket plumes. Finally, computations of ionization levels and radar cross section of a Black Brant rocket plume are presented.

Several well-known computational methods, based on various mathematical concepts, are applied to the electromagnetic scattering analysis of a benchmark cavity structure. Specifically, a simplified jet engine inlet configuration is defined, constructed and used as reference, whereas predicted numerical results for the radar cross-section are compared with measurements. The merits and drawbacks of each method are highlighted and quantified, with respect to accuracy, efficiency, resource requirements, reliability and robustness. Conclusions may be exploited in the near future in the construction of reliable classifiers, used in non-cooperative target identification

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