Quasi-one-dimensional Hugoniot analysis and scaling laws for laser-supported detonation

Repetitively Pulsed (RP) laser propulsion generates thrust via laser-supported detonation (LSD), in which an ionization front absorbing laser energy propagates at supersonic speeds to drive a shock wave. Although LSD is primarily modeled in one-dimensional frameworks, the physical mechanisms governing its multidimensional expansion and propagation modes remain incompletely understood. In this study, two-dimensional axisymmetric computational fluid dynamics simulations and a generalized quasi-one-dimensional Hugoniot analysis were conducted to elucidate the scaling laws and provide guidelines for enhancing laser propulsion performance. Varying the geometric aspect ratio of the laser heating region showed that increasing this aspect ratio drives a propagation mode transition from weak to strong detonation. At small aspect ratios, lateral expansion suppresses entropy generation and permits steady propagation in a weak detonation mode. Conversely, a large aspect ratio restricts lateral expansion, forcing the flow toward a one-dimensional state and inducing thermal choking. The resulting transition to strong detonation yields a higher isentropic stagnation pressure than weak detonation. These findings substantiate the mode-transition mechanism in LSD and show that a larger incident laser beam enhances the mechanical potential available for propulsion.