关键词: 激光烧蚀；微推进；比冲；冲量测量；烧蚀质量测量；激光推进

Abstract: The specific impulse is the important evaluation indicator of the micro propulsion performance. Its accurate measurement can not only help to analyze the mechanism of laser ablation with matter，but also help the design of micro laser ablation thruster. In order to directly measure the specific impulse in laser ablation with matter，the method adopted here is that the impulse caused by pulsed laser ablation and the gravitation caused by the loss of the ablation mass applies act respectively on the balance in the same direction and in the opposite direction based on the model of torsion pendulum in vertical direction movement，so that the specific impulse can be obtained. The results show that，the maximum angle and the angle before it can be used to calculate the impulse and the mean value of the stable rotation angle can be used to calculate the loss weight. And the structure size of the balance is the key design element in the structure design.

Key words: Laser ablation；Micropropulsion；Specific impulse；Impulse measurement；Ablation mass measurement；Laser propulsion