【作者】 何振；

【导师】 吴建军；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2008， 博士

【摘要】 本文针对激光推进应用体系所涉及的关键问题和关键技术,采用理论分析与数值仿真相结合的方法,重点开展了光船推力室构型设计、光船自由飞行稳定性分析、光船发射方案设计和弹道优化设计等研究工作。研究结果可为发展我国光船技术提供一定的理论与方法支持,并为我国开展光船自由飞行演示及微小卫星发射技术的研究奠定一定的基础。论文针对具有塞式喷管构型的光船,研究了光船推力室内激光等离子体爆轰波的演化过程。建立了基于谢多夫柱爆轰理论和冲击波反射与衰减理论的光船推力计算模型。该模型克服了计算流体力学模型计算时间长、参数难于修改的缺点,可对爆轰波演化发展全过程进行计算,适应于推力室结构参数可变时的推力计算。应用该模型对推力室构型进行了优化设计,获得了冲量耦合系数最大的推力室构型。研究了推力室结构参数对推力的影响,认识到冲量主要来源于冲击波对塞式喷管壁面的压力,提出了延长推力室工作寿命的方法。发展了光船六自由度运动模型,实现了近地面自由飞行光船的运动模拟,掌握了近地面自由飞行光船的运动规律,揭示了光船自由飞行的自稳定机理。研究表明,光船高速自旋产生的陀螺效应使光船姿态保持稳定,侧力和气动力阻尼的共同作用使光船具有稳定于光束中心的能力。分析了多种力和力矩对光船稳定性的影响,指出倾斜力矩是破坏光船姿态稳定的主要因素。提出了增强光船飞行稳定性的方法,研究结果对提高光船近地面自由飞行高度具有很好的指导作用。分析了大气对强激光传输的影响,建立了强激光大气传输模型。对基于单台地基激光器的光船发射系统进行了系统分析和设计,提出了确定激光器输出功率、推力器比冲和光船接收镜半径等关键参数的原则和方法。初步建立了光船发射的系统框架,提出了三种基于单台地基激光器的光船发射方案。研究结果对我国发展基于激光推进的微小卫星发射技术具有一定的借鉴意义。根据光船发射过程的特点和发射方案要求,建立了光船质心动力学方程,发展了基于序列二次规划法和遗传算法的光船弹道优化设计,验证了激光推进系统可获得高有效载荷比。计算了三种发射方案下的最优弹道,比较发现,相对于地面发射方案,高空发射方案可降低激光大气传输损失,入轨质量有较大的提高。研究表明,激光器输出功率大小和激光传输衰减是影响光船运载能力的主要因素。阐明了在光船初始质量、比冲和推力之间综合平衡并采用合理的发射方案和飞行弹道是改进地基激光发射系统性能的有效途径。更多还原

【Abstract】 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.更多还原