Deep space trajectory design using multiple gravity assists: A review of escape, capture, transfer, and orbit control techniques

Multiple gravity assists (MGAs) have become an enabling technology for modern deep space exploration, significantly extending mission reach while minimizing propellant consumption. This paper presents a comprehensive review of MGA-based trajectory design methodologies employed in deep space missions. A systematic classification framework is established, categorizing MGAs techniques into three fundamental domains based on their underlying dynamical mechanisms: (1) escape and capture orbit techniques, (2) diverse transfer trajectory designs, and (3) orbit adjustment and directional control strategies. Our analysis in each category connects representative methods to their real-world applications and missions. Finally, future research prospects are outlined, aiming to ultimately support the development of advanced MGA-based trajectory planning for deep space missions.