Numerical studies of ram-air Intake for near-earth satellites

Abstract

The operation of satellites in Earth orbits with altitudes lower than 450 km involves dealing with rarefied atmosphere environment. To compensate for the aerodynamic drag present in this low-density atmosphere, satellites employ traditional Electric Propulsion, EP (limited operational life) or Air-Breathing Electric Propulsion Systems, ABEP (longer operational life). Careful geometric design of intakes of ABEP systems is critical for its performance. The main motivation of this research is 1) to understand the complex flow around basic intake configurations of ABEP systems in high-speed rarefied environment- using Direct Monte Carlo Simulation (DSMC) methods, and 2) to design compression-assisted air-breathing intake geometry operating efficiently at various orbital speeds for VLEO/SLEO satellite applications. Two-dimensional axisymmetric, time-dependent Direct Simulation Monte-carlo (DSMC) method has been utilized based on open-source SPARTA DSMC Simulator for various intake geometries at three relevant altitudes. Initial simulations of basic hollow cylinder (straight duct) geometry were run, followed by an analysis of different convergent angles for converging duct intakes, for both specular and diffuse gas-surface interactions. The results have been analysed for the collection efficiencies, mass flow rates at the entry and exit planes, drag force and the number density profiles. It was observed that with increase in altitude, there is a considerable decrease in the collection efficiencies under diffuse reflection conditions, and a considerable increase of drag coefficients under specular reflection conditions