Performance characterization of intake-collectors for atmosphere-breathing electric propulsion systems

Abstract Atmosphere-breathing electric propulsion offers a promising solution for orbit maintenance in very low Earth orbit (VLEO) by collecting and ionizing residual atmospheric particles to generate thrust. The intake-collector (IC) plays a critical role in determining the propulsion system efficiency, yet experimental data on IC performance under relevant flow conditions remain scarce. This work establishes an experimental approach based on an adaptation of the dynamic method used in vacuum technology to enable direct evaluation of IC performance. We investigated plasma beam transmission through an IC model by generating an argon plasma beam with orbital-velocity ions via an RF plasma source. Different plasma conditions were established, and electrostatic probes were used to characterize the ion current density and energy distributions of the plasma beam. The transmission probabilities measured for the different plasma conditions show that transmission probability remains approximately constant despite variations in total ion current and background pressure. The measured probabilities aligned well with particle simulations accounting for space charge effects, validating our method. However, when the VLEO environment is simulated, the calculated transmission probability differs significantly from the one measured here, highlighting fundamental differences between the plasma beams in our experiments and the hyperthermal neutral flow in VLEO. Biasing the IC to mitigate space charge effects revealed a non-monotonic relationship between transmission probability and intake potential, suggesting that simple wall biasing is insufficient to replicate orbital flow conditions. While numerical extrapolation is necessary to link experimental and VLEO conditions, controlled experiments like this are essential to validate gas-surface interaction models used for high-velocity internal flows. Despite these challenges, the dynamic method adaptation developed in this study is broadly applicable to both plasma and neutral beams, providing a versatile framework for future experimental investigations in atmospheric-breathing electric propulsion systems.