Is it possible to integrate Electric Propulsion thrusters effectively on Very Low Earth Orbit Microsatellites?

点击翻译按钮获取中文摘要

This describes work to investigate the feasibility of using Electric Propulsion on Ultra Low Earth Orbit (<200km) Microsatellites (mass <125kg) effectively. The aim is to provide a highly capable satellite in the 20-100 kg range, applicable to a wide range of missions which could achieve a lifetime of at least one year in orbit.Operating a remote sensing satellite at 160km has many benefits. The closer the imager is to a target, the smaller this imager can be, leading to the possibility of using nanosatellites (<30kg) with consequent size and cost reductions. Compared to a satellite at 500 km, a Very Low Earth Orbit Satellite may achieve 3x reduction in focal length as well as up to 30x reduction in RF power with a significantly improved downlink data rate. Altogether this could lead to a 10x reduction in the overall cost.Due to increased air density at these low altitudes a satellite experiences larger drag forces which would normally cause it to de-orbit within a few months. An increased operational lifetime can be achieved using an electric propulsion system to combat the increased drag. This was demonstrated by the European Space Agency's (ESA) Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) which sustained an orbital altitude of 260km using electric propulsion for 55 months before running out of fuel.As described above, there is an interest in using orbits of less than 200km, considerably lower than GOCE, which have a higher atmospheric density and therefore higher drag. It was therefore necessary to model both the drag and orbit in order to understand the increased role that the air density played at this altitude in comparison to other perturbations of the orbit. Once the level of drag was established, the type of electric propulsion could be selected. A mapping of propulsion types to mission types was performed to aid this selection process. Modelling of the drag for the nanosatellite was achieved using direct simulation Monte Carlo techniques and this was then combined with standard orbit modelling techniques to size the electric propulsion unit.