Energetic working fluid polyazide glycidyl GAP, has attracted more and more attention in the field of laser ablation micro thruster<sup>[1-3]</sup> because it can not only absorb and utilize laser energy, but also fully release its chemical energy and participate in the process of impulse formation. In order to explore the impulse coupling characteristics of solid GAP in vacuum environment, infrared dyes with different mass fraction were doped as absorbent. In a vacuum chamber with a pressure of 30 Pa, a 1064 nm Nd: YAG laser was used to test different laser energy modes (transmissive and reflective) for different thicknesses and different doping concentrations at different laser energy densities. The results show that the doped infrared dye can not significantly change the absorption threshold of laser energy by GAP, but significantly increases the deposition of laser energy in GAP. The doping concentration has a great effect on the coupling performance of the pumping amount within a certain concentration range. When the doping concentration is 5%, the momentum coupling performance of laser ablation GAP is optimal. The thickness of the GAP with the best impulse coupling performance is related to the doping concentration. The higher the concentration, the smaller the thickness of the GAP with the best ablation performance. When doped with infrared dye, GAP exhibits the body absorption characteristic of laser energy, which follows the injection mechanism of “first absorbing laser energy first injection”, so the reflective ablation mode exhibits better propulsion performance.
The propulsive properties of the energetic polymer glycidyl azide polymer (GAP) doped with carbon nanoparticles in the transmission mode were studied and a 1064nm Nd:YAG laser with a pulse width of 9ns was selected. According to the Propulsion performance parameter of GAP with different carbon nanoparticles contents and thickness, combined with plume image, the reasons for improving the propulsion performance of laser ablation GAP by carbon nanoparticles doping are analyzed and the design scheme of the structure composition of the polymer target is preliminarily explored. The experimental results show that the 1064nm laser absorption of the polymer GAP is greatly enhanced and the propulsion performance is obviously improved after doping with carbon nanoparticles, but the propulsion performance of the polymer can not be significantly improved by increasing the carbon contents higher than 1%. The GAP after doped with high carbon nanoparticles contents exhibits metal-like surface absorption characteristic and the absorption depth to laser decreases. Under the transmission mode, with the increase of target thickness, the incomplete ablation mass increases, which greatly reduces the utilization ratio of GAP. The optimal ablation efficiency of GAP target with thicknesses of 54μm was more than 250%, and plume images showed that ablation and decomposition were very sufficient. It is appropriate for the target of laser ablation micro thruster.