Beam Riding Performance of Asymmetrically Propelled Laser Vehicle

Abstract

To improve the in-air flight performance of a laser propulsion vehicle, it is helpful to develop a computational model that can reproduce full dynamics, including impulsive vehicle motion driven by interaction with a blast wave. The authors have developed a three-dimensional hydrodynamics code coupled with six-degree-of-freedom equations of motion of a laser propulsion vehicle for analyzing flight dynamics through numerically simulating flowfield interacting with unsteady motion of the vehicle. Using ray tracing, asymmetrically deposited energy corresponding to laser offsets was initially added to the flowfield around the vehicle to estimate beam riding mechanics against lateral or angular offset, and a combination of them for a single pulse. The centering performance of the lightcraft is excellent for lateral and combined offsets, but the recentering force becomes weak with a large angular offset. If the vehicle inclines toward the axis of the incident laser beam, an angular restoring moment is generated to reduce the angular offset. Also, flight dynamics simulations were performed for multiple pulses by integrating aerodynamic responses based on single-pulse results, and spiral-flight motion and deviation from the laser path were successfully reproduced. When the laser axis is rotated following the gyro motion of the vehicle, the angular restoring moment is maintained for a longer time, and the vehicle is able to fly to a higher altitude.