Analysis And Design Of Laser-propulsion Lightcraft's Configuration And Ground Based Laser-propulsion Launching Mission

Under the background of developing laser propulsion technology and applying it into launch of micro-satellites, this dissertation makes some investigation to such some special tasks as lightcraft's thruster configuration, stability analysis on lightcraft's free flight, trajectory optimization and launching scheme's design by integrating theoretical analysis with simulation computation. The results can provide some theoretical and methodology's support for developing lightcraft technology, and can lay an important foundation for the free flight of lightcraft and the ground-based laser launch missions in our country.For a lightcraft with plug nozzle, the process of laser supported detonation wave converting into impulse was investigated. A model for thrust calculation was set up by combining Sedov's theory of self similarity solution for line explosion with shock wave theory of reflection and attenuation. The model can perform well for simulating the evolution process of blast wave when thruster's structural parameters were variable. However, for the CFD model to simulating the same task, it's very time-consuming and difficult to change the concerned parameters. A set of the optimum structural parameters of thruster's configuration had been obtained with this model. The structural parameters'effect on impulse was also investigated. It's found that the impulse mainly comes from the pressure on the plug nozzle. Some ways to extend the service time of the thruster were proposed.A six-degree of freedom model of lightcraft was developed and the simulation of motion process was performed for the lightcraft's free flight. The movement of lightcraft's free flight was analyzed and the mechanism of stability for lightcraft's free flight was opened out. The results show that lightcraft's attitude stabilization is achieved by gyroscopic effect, and that due to the side force and the aerodynamic damp, lightcraft has the ability to ride a laser beam. The impulsive reaction applied to the lightcraft and the aerodynamic force was examined. It's found that the pitching angular impulse is the main factor that caused the change of attitude. To increase the height of free flight, some approaches to enhance the stability of lightcraft were also proposed.Atmospheric propagation effects of high energy laser beam were discussed in detail. A propagation model of high energy laser beam was set up. The principle and method to choose some key parameters, such as laser power, specific impulse and the radius of nozzle, were discussed and proposed. The framework on lightcraft orbital launch system was analyzed and discussed. Three kinds of solution for lightcraft orbital launch were proposed. The investigation may provide some valuable suggestion for the realization of single laser orbital launch.A model for lightcraft's flight process was developed based on the characteristics of lightcraft and the launch system. The optimal control problem on the maximum payload for launching lightcraft into LEO was solved by using sequential quadratic programming and genetic algorithm respectively. The trajectory optimization was performed by three kinds of solution for ground-laser-based lightcraft launching schemes. The results show that laser propulsion system's payload ratio is very high. Compared with the lightcraft launch scheme from ground, the launch scheme from 30km altitude with a relay mirror can reduce the atmospheric propagation loss for high energy laser beam and increase the mass to orbit. The trajectory computation show that the laser power and the atmospheric propagation of high energy laser beam are such some crucial factors that they almostly restrict the ability of the launch system. A way to increase the ability of launch system is to make some trade-off among such some main parameters or factors as initial mass, specific impulse, thrust and employ an optimal trajectory.