Laser thrusters with single nozzle of parabolic or conic profile fail to constrict the high-pressured flow efficiently, resulting in poor propulsion performance. Under air-breathing mode and different single-pulse laser energy, the laser thruster with elongate cylindrical nozzle which features a parabolic nozzle tailed by a cylindrical nozzle is studied numerically for different shape parameters by building physical computation model. Readily, its impulse coupling coefficient is tested to be more than 600 N/MW with a good accordance with the foreign experiments. Meanwhile, the results show that, the impulse coupling coefficient increases along with cylindrical nozzle length and approaches a constant value, and the proposed cylindrical nozzle saturation length increases linearly with laser energy; the impulse coupling coefficient increases initially but then descends as the parabolic expanding-angle increases, and the half-expanding angles corresponding to the peak stay around 33° with little variation when laser energy differs for the total nozzle length of 100 mm; as the ignition position moves farther away, the impulse coupling coefficient also reaches a peak-corresponding, and the peak ignition position shows a linear relation with laser energy.%针对抛物形喷管与圆柱形喷管相组合的带延长圆柱形喷管激光推力器模型,通过求解含激光能量源项的流体力学方程组,计算得到了不同单脉冲激光能量条件下3种构形参数对冲量耦合系数和推力的影响.结果显示带延长圆柱形喷管可获得高于600 N/MW的冲量耦合系数,同时表明冲量耦合系数随圆柱喷管长度的增加而增大并趋于饱和,圆柱喷管饱和长度与激光能量呈线性关系.冲量耦合系数随抛物形喷管张角的增大先增大后减小,对于总长度为100 mm的喷管,半张角在33°左右时取得最大值且受激光能量的影响很小.冲量耦合系数随点火位置的增大也存在最大值,最大值对应的点火位置与激光能量成线性关系.
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