Reentry Trajectory Design with Pigeon Inspired Optimization Using Derived Angle of Attack Profile

This paper proposes two strategies that generate the entry trajectories using pigeon inspired optimization (PIO) for a lifting type reentry vehicle. The obtained entry trajectory should be within the entry corridor formed by the specified upper bounds on heat rate, dynamic pressure, and load factor. In both the approaches, bank angle which is parametrized to be a linear function of energy and angle of attack are considered as the control variables. This paper presents a methodology that converts the path constraints to allowable bounds on the angle of attack. The angle of attack at any instant is obtained by using the load factor constraint in the first approach and in the second approach, the angle of attack is obtained using the heat rate and load factor constraints. Hence, the path constraints are satisfied by modulating the angle of attack alone. In both cases, bank angle is suitably modulated to achieve the desired terminal range-to-go and also to maintain the equilibrium glide condition. The terminal heading angle offset is minimized using traditional bank reversal logic. These two scrategies are simulated for common aero vehicle (CAV-H) with a high lift to drag ($\mathrm{L}/\mathrm{D}$) ratio. Simulation results show that the entry trajectories obtained using the PIO algorithm have satisfied the path constraints and achieved the terminal range-to-go accurately.