Flow and Impulse of Annular Laser-Pulse-Induced Explosions on a Sphere

A donut-sphere laser launch system has been suggested for launching a sphere capsule stably along an annular cross-sectional "donut" laser beam. In this study, the thrust and side force are numerically investigated using a simple explosion source model considering the beam size, explosion source energy, and axial offset between the beam and target as the parameters. It is established that the thrust, as well as the side force, is sensitive to the ratio of the laser-beam radius to the sphere radius RL*. The impulsive thrust force is maximum at RL*=0.5 approximately, whereas a positive side force (i.e., recovery force) can be generated only if RL* is greater than a critical value of approximately 0.8. These trends are explained with respect to shock focusing and laser ablation.