在喷管与聚光系统一体化设计时,聚光系统因其同时承担聚光和喷管两项功能而成为激光推力器的重要组成部分。通过改变聚光系统内表面的母线方程,可以改变点火区的大小、形状、点火区与聚光系统内表面的距离及喷管长度等参数,而这些参数都会对激光推力器的推进性能产生影响。针对不同的聚光系统构形建立了相应的点火模型,数值计算与实验结果一致,即当注入能量不超过60 J时,在喷管出口直径相同的条件下,抛物形喷管点聚焦方式比环聚焦方式所获得的冲量耦合系数大,可达38.84×10-5 N·s/J;而冲量耦合系数对点火区与聚光系统内表面的距离及喷管长度等参数并不十分敏感。研究结果对于吸气式激光推力器的喷管构形设计具有指导意义。

Focusing system is one of the most important components of laser thruster when it is also used as a nozzle at the same time. Such parameters change with generatrix equation of inner surface of focusing system as the shape and the size of ignition zone, nozzle length and the distance between ignition zone and inner surface of nozzle. All these parameters have effects on the propulsion performance of laser thruster. Four kinds of ignition modes are set up according to different nozzle structures. The results of numerical calculation and experiment are coincident. When injecting energy is not larger than 60 J and the diameter of nozzle exit is constant, the impulsion performance of laser thrusters with a parabolic focal point is found better than that of those owing a round one, and the coupling coefficient of the former is about 38.84×10-5 N·s/J. And the impulse coupling coefficient is not sensitive to nozzle length and the distance between ignition zone and inner surface of nozzle. The results are very useful to design nozzle structure of laser thruster that works in air-breathing mode.