地基激光器发射微卫星的方案设计与弹道优化计算

Conceptual design of system and trajectory optimization for ground-based laser propulsion

用地基激光器发射近地轨道卫星是激光推进应用体系概念研究的热点。对发射方案的分析可知比冲、冲量耦合系数、飞行器水平飞行距离、光束天顶角等参数对激光推进发射方案具有重要影响。基于地球平面假设,针对Myrabo发明的吸气式光船,在比冲恒定、激光功率为20 MW的条件下,用序列二次规划法计算了光船初始质量为100 kg,先后采用吸气和火箭模式从地面发射到200 km圆轨道的最优弹道。作为比较,还计算了光船从地面起飞全火箭模式的最优弹道。计算结果表明,光船采用吸气和火箭双模式的发射方案时能获得较大的有效载荷比,光船入轨质量可以达到35.5 kg。

Ground based laser propulsion system is studied intensively in recent years. The specific impulse, momentum coupling coefficient, lightcraft＇ s horizontal distance from the laser platform is of great importance for launching systems. Myrabo＇ s Lightcraft may be a convenient vehicle for launching micro-satellite to LEO. A 20 MW pulsed laser under the invariableness of specific impulse is employed to launch a lightcraft with 100 kg initial mass to 200 km circular orbit, the lightcraft＇ s trajectory is computed. In another case the lightcraft is launched from ground using only ablative propulsion mode. Based on the assumptions such as the surface of the earth is fiat and the specific impulse is constant, the simplified form of the equations of motion of lightcraft can be obtained. Then, the sequential quadratic programming is used to numerically solve the maximum payload-to-orbit optimal control problem. The result shows that using two propulsion modes can obtain larger payload ratio, and the maximum payload-to-orbit can be up to 35.5kg.