Propellantless Technology for the Deorbiting of Small Satellites Mega-Constellations at the End of Life

Deorbiting performance of 200-kg class satellites from different critical altitudes and inclinations using bare electrodynamic tape tethers is discussed. The study leads from the recent interest of several companies worldwide in building of mega-constellations composed of hundreds of microsatellites. Using as input the limited information that can be presently found in open sources, three representative mission scenarios for mega-constellations are studied in this paper considering a constant satellite mass of 200 kg. In the first step, an optimized tether geometry is found using the BETsMA optimization software assuming the spacecraft mass, the starting altitude, and the orbital inclination as inputs. The output of this phase is the conductive tether length, width, and thickness and an estimated cut probability due to hypervelocity impacts during deorbiting. In a second step, the system configuration is further refined by means of extensive numerical simulation campaigns performed with the Flexible Tether Simulator for electrodynamic tethers software that models the tape tether with a discrete number of lumped masses. This accurate simulation code take into consideration both tether longitudinal and lateral modes of vibration and employs the latest Earth magnetic field, ionospheric electron density, and atmospheric models to simulate a realistic in-orbit environment. Moreover, it enables the simulation of tether motion control strategies that can be used to increase the system reliability and efficiency. The final goal of this study is to find a comparatively light system configurations that can perform a complete deorbit of a 200-kg microsatellite in the shortest possible time from different starting altitude and inclinations. The results of the study show that the electrodynamic tether option is attractive compared to deorbit systems based on traditional chemical fuel.