Thermophysics Universal Research Framework (TURF) is an in-house framework developed at the In-Space Propulsion Branch of the Air Force Research Laboratory. The spacecraft module of TURF contains special operators to enable the simulation of an electric propulsion plume. This module has been extended to perform the surface potential calculation based on the charged species currents to the surfaces. The charging models implemented are (1) dielectric, (2) conductive, and (3) charge propagation. In this paper, the surface charging models and the calculations of ion and electron currents to surfaces are described. The charging model is tested for a conductive geometry in a quiescent plasma. For a plasma density of 10~(12) m~(-3), the floating potential is correctly obtained. The charging model is also run with an electric propulsion plume simulation. It is shown that the treatment of geometry boundary cells has significant effects to the ion currents, surface potential, and sputtering of spacecraft components.
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