Beam-riding flight of a laser propulsion vehicle using actively controlled pulse

This paper discusses active laser control using a genetic algorithm and a mirror-actuating system to achieve kilometer-order in-air flight using a laser propulsion vehicle while riding a beam. A 10 kg vehicle reaction driven by a strong shock wave is examined using our flight simulator to analyze interaction with unsteady blast wave propagation based on coupling calculation between hydrodynamic simulation of the shock wave propagation and orbital simulation of the vehicle flight motion, and the generated impulses are characterized by the spherically symmetric Sedov solution. Beam-riding flight with an initial y offset of 5 mm is successfully sustained by controlling angular offset, while vehicle acceleration is kept low for safe launch to the target altitude. A system delay of laser control is introduced into the flight simulator, and beam-riding flight is maintained for a 20 ms system delay using delay correction following prediction by six-degree-of-freedom equations of motion. This study also examines robustness of the flying technique for wind perturbation, and an active control scheme that can ensure stable flight with a wind of up to 40 m/s. The stability of flight control is assessed when there is a positioning error of laser incident light, and flight is stably sustained by keeping the angular offset small for the positioning error with a standard deviation 1 cm. This paper examines the lower limit of repetition frequency of multiple pulses for stable flight, and found that a repetition frequency exceeding 15 Hz should be selected in order to maintain posture stability. Stable flight is not maintained for the combination of larger system delay and positioning error because translational velocity and angular offset simultaneously increase. However, the vehicle can fly to kilometer-order altitude while maintaining posture stability if the translational and angular impulses are adjusted. Flight performance can be improved by adjusting impulse direction and size using our flight simulator as an impulse design tool.