Particle-in-Cell simulation of the flow in the VKI DRAG-ON facility

A facility for the reproduction of orbital flows, named DRAG-ON, has been successfully commissioned at VKI. The facility is designed to test intake-collectors for Air-Breathing Electric Propulsion applications. Relevant properties of intake models, such as their transmissivity and compression efficiency can be measured. The flow of fast neutrals encountered by a satellite in orbit is reproduced by a quasineutral plasma flow (of Ar or O₂/O ions), generated and electrostatically accelerated in a plasma source. Understanding the dynamics of the expanding plasma plume and its interaction with the intake model is fundamental for the correct interpretation of the experimental results. We use the Particle-in-Cell method to replicate numerically part of the experimental setup and assess these effects. An advanced implicit, energy-conserving scheme on unstructured grids is used to mitigate the numerical difficulties arsing from the multiscale nature of the plasma. Some undesired effects, such as the expansion of the plume due to the residual electron pressure and the deflection of ion trajectories due to the presence of plasma sheaths on the surface of the intake model are identified and analyzed.