Direct simulation Monte Carlo-driven optimization of vacuum intakes for air-breathing electric thrusters in very low earth orbits

The performance of an atmosphere-breathing electric propulsion (ABEP) intake has been investigated with a focus on the direct simulation Monte Carlo (DSMC) method. A numerical dataset was derived from extensive DSMC analysis of rarefied flow across various intake configurations. The intake geometry, based on a concept from the literature, comprises a cylindrical body with four annular coaxial channels and a conical convergent diffuser. By maintaining the aspect ratio of the coaxial channels, the DSMC simulations were performed by changing three key parameters: inlet area, convergent diffuser angle, and operating discharge voltage, at altitudes ranging from 140 to 200 km. The analysis of the ABEP system revealed that altitude has the most significant influence on the discharge power, while the effects of the diffuser angle and inlet area are comparatively smaller. Analysis at fixed altitudes reveals a strong influence of altitude on discharge power, while the diffuser angle and the inlet area play a minor role. The results also show that the sensitivity of the discharge power to the diffuser angle increases as the altitude approaches the highest level of 200 km. Furthermore, an evolutionary-based optimization methodology was applied, taking into account the requirements of a drag-to-thrust ratio of less than 1 and a discharge power of less than 12 kW. Optimization analysis in the full altitude range revealed that the optimal diffuser angle falls within the narrow range of 15°–20°, corresponding to an optimal operating altitude range of 170–178 km.