Very low Earth orbit (VLEO) satellites are confronted with the challenge of orbital decay caused by thin atmospheres, and the volume and power limitations of micro satellites further restrict the application of traditional electric propulsion systems. In response to the above requirements, this study proposes an innovative scheme of radio frequency plasma micro-thrusters based on magnetic nozzle acceleration technology. By optimizing the magnetic nozzle configuration through the system, the plasma confinement efficiency was significantly enhanced. Combined with the mixed working medium (5 sccm Xe + 10 sccm air), the thrust reached 1.7 mN at a power of 130 W. Experiments show that the configuration of the magnetic nozzle directly affects the plasma beam morphology and ionization efficiency, and a multi-magnet layout can form a stable trumpet-shaped plume. The air in the mixed working medium has a linear relationship with the thrust gain (60 μN/sccm), but xenon gas is required as a “seed” to maintain the discharge stability. The optimized magnetic nozzle enables the thruster to achieve both high thrust density (13.1 μN/W) and working medium adaptability at a power level of hundreds of watts. This research provides a low-cost and miniaturized propulsion solution for very low Earth orbit satellites. Its magnetic nozzle-hybrid propellant collaborative mechanism holds significant engineering significance for the development of air-aspirating electric propulsion technology.

Bénard–Marangoni convection in thin liquid layers on hot spherical cap substrates is numerically investigated in this study. The liquid–air surface is cooled by air, the sidewalls are adiabatic, and the spherical substrates are isothermally heated. In numerical simulations, the range of Marangoni number at the sidewall (Mar) is 10 to 7000, and the Prandtl number is 29. For small Mar, the temperature field, accompanied by weak thermocapillary convection, is dominated by conduction. As the Marangoni number increases, thermocapillary convection becomes stronger. A weak flow pattern may appear at the position where the liquid layer is thickest, whereas conduction still dominates in the thinner region of the liquid layer. The onset of the Bénard–Marangoni convection takes place, and hexagonal cells form when Mar increases to the critical Ma (Mac), yet conduction still dominates in the thinner region of the liquid layer. The flow becomes periodic between Mar = 128 and 136. When the local Marangoni number at the thinnest part of the liquid layer increases to Mac, the convection cells cover the entire surface. With the further increase in the Marangoni number, the morphology of convective cells gradually transitions from hexagons to quadrilaterals and then to irregular polygons. The convection may sequentially become periodic, quasiperiodic, periodic, and quasi-steady. When the Marangoni number is sufficiently large, subcells and hydrothermal waves occur.