脉冲激光推进的能量相似律理论研究

Theoretical analysis of energy law of similitude of conical nozzles for laser propulsion in repetitively-pulsed mode

激光推进的能量相似律,指确定的激光能量有与之相对应的最佳喷管尺寸,使得冲量耦合系数最大且不变的规律。用大气高度参数、入射的激光能量、喷管几何参数构造了无量纲因子,建立了圆锥形喷管在单脉冲条件和一维球对称点聚焦情况下的能量相似律。结果表明:当锥角固定时,冲量和冲量耦合系数存在极大值,极大值对应的无量纲因子仅与气体比热比相关;当无量纲因子固定时,冲量随入射激光能量增加而单调增大,冲量耦合系数则与能量无关。本文的研究结论和规律性认识,对目前可实现和以后工程化放大的激光能量范围,均能给出可信可靠的喷管优化尺寸。

Energy law of similitude for laser propulsion refers to that there is an optimum nozzle size for fixed laser energy,making impulse coupling coefficient remaining the largest. A dimensionless factor coupling incident atmosphere altitude,incident laser energy and nozzle geometry parameters is introduced,and energy law of similitude of conical nozzles is created with a single laser pulse and by a laser focusing on a sphere region. The results show that impulse and impulse coupling coefficient firstly increase and then decrease with augment of the dimensionless factor when cone angle is fixed. Impulse increases monotonously with enhancement of incident laser energy,while impulse coupling coefficient is independent of it,when the dimensionless factor is fixed. The authentic and reliable optimum nozzle sizes can be obtained for laser energy.