Micronozzle for satellite propulsion and mixture separation: a review

Micronozzles operating with vacuum exit conditions find applications in satellite propulsion systems and aerodynamic separation processes. The increased demand for cube satellite applications and the need for real-time fast response sensors for monitoring pollutants and toxic releases have created interest in micronozzles operating under multi-scale flow regimes. The objective of this paper is to present a summary of the research on supersonic micronozzles that operate with vacuum exit conditions and are utilized in applications such as satellite attitude control, deep space probes, and binary mixture separation. The review covers various experimental programs and numerical techniques employed, along with analyzing the flow characteristics and their influence on the nozzle's performance. A brief description of experimental techniques adopted, trends in numerical methods, and the effect of various parameters such as size, shape, expansion ratio, surface roughness, Re, and wall heat transfer have been included. The review of simulation studies focuses on the DSMC method, the various approaches for modeling collision between particles, particles, and walls, and the simulation strategies. Comparisons are made to understand how well the DSMC method can predict the flow. The current understanding of the flow behavior under various exit conditions is summarized. Major flow features, experimentation, simulation approach trends, design considerations, manufacturing methods, etc. are discussed. The review concludes by discussing the ongoing and future challenges, especially regarding experimental measurements in a vacuum and reducing computational expenses.