Coupled Attitude-Orbit Control of Flexible Solar Sail for Displaced Solar Orbit

The solar sail is a new type of spacecraft for deep space exploration that is propelled by solar radiation pressure. The solar sail is large, has a large moment of inertia, and is highly flexible, and its motion involves a coupling of the orbit, the attitude, and structural vibration. With the coupling effect of the orbit and the attitude included, a non-Keplarian displaced solar orbit is designed. In the rotating frame, the solar sail has a stable equilibrium point, and an attitude controller is employed for coupled attitude-orbit control. With control, the time required for eliminating the orbital deflection is much larger than that required for the attitude deflection. Including the additional influence of the flexibility of the solar sail, the structure shows a sustained, high-frequency vibration, which also leads to sustained and high-frequency likewise small vibrations of the orbit and attitude. This work demonstrates the importance of including the structural flexibility into the coupling effect of the solar sail for long-term missions in space.