Ground to orbit launch using laser propulsion requires a thermal system. Physically allowed thermal concepts are discussed and compared. It is argued that the laser supported detonation (LSD) mechanism presents a number of advantages over the alternatives. Numerical simulations of ascent trajectories for a system based on the LSD mechanism were performed to gain insight into the mechanics of laser propulsion and the influence of the most relevant mission parameters. Comparison with the Lightcraft flight data was made and it is shown that the 70 meter height limit is due to excessive laser diffraction. A hypothetical 10 km Lightcraft simulation employing existing technology is presented. @en