Attitude Simulation and Design of Passively Stabilized Drag Sails

Kurzfassung

The rapid increase in the number of satellites, especially those in low Earth orbit, has led to a significant increase in space debris. This has raised concerns about the sustainability of space operations, as outlined in the European Space Agency’s Zero Debris Charter. Reflective flat drag sails are the state-of-the-art for accelerating the deorbit process of non-operational satellites. Previously, they were thought to be subject to chaotic tumbling motion, which limits their deorbit efficiency. However, a critical knowledge gap exists regarding the true attitude dynamics and aerodynamic stability limits of various sail geometries. To address this gap, a numerical attitude simulation tool was developed. This tool calculates the attitude dynamics of a discrete spacecraft model. It explicitly accounts for aerodynamic effects, solar radiation pressure, and gravity gradient disturbance torques, as well as shadowing effects from the first two. The simulation incorporates three standard atmosphere models: NRLMSISE-00, NRLMSIS 2.0, and JB2008. The thesis evaluates flat and pyramid geometries with reflective and transparent membranes. It has been demonstrated that transparent sail membranes generally outperform reflective state-of-the-art membranes. In compliance with literature, pyramids with a 70° apex halfangle have shown the largest stabilization capabilities. Despite their generally lower stability, flat sails are preferred for dusk-dawn orbits below 430 km. Although their stability relies entirely on environmental equilibrium, they effectively utilize a larger portion of their drag area for ideal initial deployment. This study shows that flat sails only achieve an equivalent magnitude of dominant aerodynamic stabilization at an altitude about 150 km lower than that of the 70° pyramid. Drag sails are generally applicable up to an altitude of 450 km in the case of low solar activity. Generating robust deorbit predictions at altitudes above will require the future implementation of a coupled altitude-and-attitude numerical propagator.