Aerodynamics of inflatable nano-satellite “EGG” in low earth orbit and reentry duration

Abstract

An inflatable nano-satellite with thin-membrane aeroshell, “EGG”, was deployed from the International Space Station at an altitude of approximately 400 km, as part of an orbital deployment mission in 2017. After flight on the low Earth orbit (LEO) for 120 days, EGG successfully reentered Earth’s atmosphere and burned out according to mission schedule. During the mission period, surface temperatures of the membrane aeroshell of EGG were measured using thermocouples. The measurement data was sent to the ground station using Iridium short burst data communication. There has not been sufficient investigation of the aerodynamic heating environment of such inflatable vehicles. In this paper, the heat flux on membrane aeroshell was revealed, based on the measured temperature data and a heat conduction simulation technique. In addition, heat flux distributions at an altitude of 120 km were numerically evaluated using the Direct Simulation Monte Carlo (DSMC) method, for cases where the angle of attack was between 0 and 180°. From the reconstructed heat flux history and the DSMC analysis results, it was found that the heat flux on the inflatable torus was higher than that on the membrane aeroshell. Additionally, it was concluded that EGG was in the heating environment of approximately 3-4 kW/m2 at an altitude of 110 km.