A Nonfixed-Duration Turn-Based Orbital Game Algorithm Based on History-Aware and Predictive Result Reward Proximal Policy Optimization

Orbital pursuit–evasion games have attracted increasing attention in recent years. Most existing studies focus on extremely close-range continuous maneuvering scenarios, while medium- and long-range impulsive maneuvering problems are often studied under simplified assumptions, such as synchronous decision-making and maneuver execution, or fixed information measurement delays. In practice, however, satellite maneuver execution typically lags behind decision-making due to control delays and decision validation processes, and the measurement of orbital information is also subject to non-fixed delays caused by environmental and operational factors. To account for this characteristic, this paper considers a non-fixed-duration turn-based orbital pursuit–evasion game setting, in which decision-making and maneuver execution do not occur synchronously and the execution delay is determined by the spacecraft itself. Within this setting, a History-aware and Predictive Result Reward Proximal Policy Optimization (HPRR-PPO) method and an alternating reinforcement learning training scheme are developed. By introducing a predictive result reward and a history-aware terminal reward, the proposed method provides more informative learning signals under non-fixed-duration turn-based interactions. Simulation results demonstrate that the proposed approach achieves better task performance and training efficiency than several baseline methods in the considered orbital pursuit–evasion scenarios.