激光推进中激光波长对推进效应的影响

Effects of laser wavelength on laser propulsion characteristics for laser propulsion

针对"烧蚀模式"激光推进,为了精确计算靶材的烧蚀质量以得到较准确的比冲值,采用了平衡气化和"电子崩"等简化模型描述激光等离子体的形成,初步实现了固体靶的激光动态烧蚀物理过程。同时采用光线跟踪的思想计算了等离子体的对激光脉冲的逆轫致吸收过程,重点计算和分析了激光波长对推进效应(冲量耦合系数Cm和比冲Isp)的影响及其机理,结果表明:随着波长的增大,Cm减小,Isp增大;波长为2.5μm处的能量利用率η最高,达到了97.8%。

To calculate the ablated mass of target accurately and obtain the exact Isp, the equilibrium evaporating model and electron cascade＂ growth model were considered to describe the formation of laser plasma in ＂ Ablation model＂ laser propulsion. The physical process of laser dynamic ablation for solid target was realized preliminarily. At the same time, the energy of laser pulse absorbed by plasma through inverse-bremsstrahlung was calculated by ray-tracing metnod. The effects and mechanism of laser wavelength for laser propulsion characteristics,which are momentum coupling coefficient Cm and specific impulse l p were analyzed by simulating calculation. The results show that Cm increases and Isp decreases with increasing A, and the ablative efficiency η achieves its maximum 97.8% at λ =2.5 μm.