Guidance Method Of Fast Fly-Around Relative To Target Spacecraft

With the continuous development of space technology, the proximity operations of small satellites has been widespread concerned at home and abroad, the mission of flying around a non-cooperative target is an important part. Fly-around is a relative motion that one space vehicle (named the chaser) flies around the other satellite (named the target) periodically, it plays a key role in many current space operations such as rendezvous and docking, formation flying, target detection and satellites repairation. In this study, the fly-around mission for the non-cooperative target is taken into account, the fast guidance strategy and the fast fly-around maneuvers are studied, respectively. The main contents include:Firstly, the relative motion model of the chaser and the non-cooperative target is established. For the different stages of the fly-around process, the C-W equations and LOS guidance equations are presented to describe the relative motion; and then concerned with the practical engineering background, the chaser's navigation devices and engines configuration are programed, and the LOS information equations are solved for providing basis to design the guidance strategy.Secondly, the fast guidance strategy is designed for the short-range rendezvous stage. First, a sufficient condition of natural fly-around is derived, which is also considered as the terminal condition of the rendezvous stage; then the guidance strategy is proposed, the guidance laws of the strategy is analyzed and designed, and the switch condition of the two laws is discussed. A numerical simulation is proposed to verify the validity of the guidance strategy at last.Thirdly, the water-drop fly-around and the bi-elliptic flyaround maneuvers are studied for realizing the fast circumnavigation of the target. The extend relative orbital elements are presented to discribe the fly-around orbit, compared with the traditional method using relative position and relative velocity, the relative orbital elements can demonstrate the orbit's information more visually, and then the fast fly-around orbits are designed using extend relative orbital elements. Finally, the superiority of fast fly-around maneuvers is verified through simulation comparasion with the natural fly-around.Finally, the chase's attitude requirment is studied for the two stages. In the short-range rendezvous stage, the LOS angular velocity and acceleration is analyzed to design the attitude system. Then the angular velocity in the fly-around stage is deduced using the extend relative orbital elements for the attitude control system.