管中激光加速器的推力形成过程

Thrust Forming Process in Laser-driven In-tube Accelerator

管中激光加速器是一种新型的激光推力器,弹射体在管道中被加速。利用光线追踪法,根据光线在网格中的传播路径信息,运用辐射输运方程,得到流场的能量源项;数值求解含能量源项的流体控制方程,对管道中等离子体流场激波的形成和演化过程进行了研究。模型能够模拟空气光学击穿、空气对激光能量的吸收、等离子体对激光的屏蔽作用和推力形成过程,通过计算得到冲量耦合系数为3.61×10-4N/MW,等离子体内能转化为流场动能的比例约为9%。

Laser-driven in-tube accelerator is a new-style laser propulsion thruster characterized by accelerating projectile in a tube. With the ray tracking method,tracks of the rays in the grid are used to compute the energy source term by radiation transfer equation. The control equations with energy source term are solved numerically,through which the features of the generation and evolvement of the laser-induced shock waves in the tube are studied. Processes including air optical breakdown,absorption of laser energy,plasma shielding of the laser beam and thrust forming are reproduced. Numerical results indicate that the obtained momentum coupling coefficient is 3.61×10-4 N/MW,and the conversion efficiency of plasma internal energy to fluid kinetic energy is about 9%。