A Model of Ablative Capillary Discharge (Preprint)
AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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An engineering model of a steady capillary plasma discharge is presented. Two regimes of operation are studied and compared, differing by the assumptions made in the treatment of the radiative fluxes. In the first case, the plasma density is high enough that the radiation Rosseland mean free path is smaller than the capillary radius this case of black-body radiation leads to super-high pressures. In the second case, the radiation mean free path is larger than the capillary length, and the limit of volume radiation is achieved, leading to more moderate pressures. Both assumptions lead to different scaling laws, with consequences for the capillary design. The current model is based on the conservation laws for mass, momentum and energy, and assumes local thermodynamic equilibrium LTE and sonic conditions at the exit plane. Various assumptions have been made in the literature about the amount of heat being used for the phase change and the ionization cost of the wall material, and the effect of these assumptions is also examined. Finally, we discuss a number of potential applications of the discharge, describe planned experiments, and discuss on-going work in extending the model to multi-dimensions and the intermediate between black-body and volume radiation regime.
- Numerical Mathematics
- Radiofrequency Wave Propagation
- Electric and Ion Propulsion