Research On Impulse Generation Mechanism Of Pulsed-Laser Ablation Propulsion

This thesis is dedicated to the research of impulse generation mechanisms of laser and material interaction.First the impulse generation process of nanosecond laser ablation of energetic polymer is modeled; Laser material interaction theory and modeling method are expatiated. The thermodynamic processes versus time of dense phase and plasma under laser illumination are analyzed. The result shows that during the laser illumination the pressure of ablation plane are so high that the main impulse is generated at this time.Then the thesis performs image taking of plasma plume which obtains the whole process of plasma movement, form beginning to the end. Using nanosecond resolution intensified CCD camera to take the image of emission light of plasma. The result shows that there exists different plasma under air and vacuum condition, solid grain mix in the plume. Main impulse is generated during laser pulse width and the very time followingAt last, the thesis carries out the experiments of ms and ns laser ablation to analyze different impulse generation process via performance parameters impulse coupling coefficient and specific impulse. This experiment utilize nN·s resolution torsional pendulum measure ablation micro-impulse. The result shows that different mechanisms of impulse generation exists between ms low power density laser ablation and ns high power density laser ablation. Thermal heating effect inducing propellant gasification is mainly responsible for the former while plasma absorption of laser energy are for the latter.