Impulse coupling characteristics of GAP, PTFE and aluminum with laser ablation

Abstract

Laser ablation propulsion and pulsed plasma propulsion are both valuable and effective space propulsion systems for microsatellite, which have the advantages of light weight, small structure, wide thrust range, high specific impulse, high control accuracy and so on. Combing the laser ablation propulsion and pulsed plasma propulsion to be a laserelectromagnetic hybrid pulsed plasma propulsion has been a novel system of propulsion, which has got great attentions around the world these years. It is an important research topic in laser propulsion field to find high performance ablative working material. Energetic polymers such as Glycidyl Azide Polymer (GAP) is an excellent working material, which exhibit excellent performance due to the release of chemical energy during the process of laser ablation. Polytetrafluoroethylene(PTFE, Teflon) is widely applied in the research of pulsed plasma thruster(PPT) because PTFE is easy to ionize under arc discharge and its chemical state is stable in both vacuum environment and normal environment. Aluminum has been proved to have great performance in laser ablation and laser-electromagnetic hybrid pulsed plasma propulsion. A laser ablation system was established to research the impulse coupling characteristics of GAP, PTFE and aluminum, all of which were used as propellant under the irradiation of different laser intensity. To evaluate the propulsion performance of the propellant, a torsion pendulum measuring system was established. Thrust and impulse coupling coefficient were obtained. The results show that GAP, PTFE and aluminum all got better thrust effect while the laser intensity increased. GAP got the best performance in thrust with the help of the release of chemical energy while aluminum did the worst. Impulse coupling characteristics of three working materials were the same trend that with the increase of laser intensity, impulse coupling characteristics were all rising rapidly at the very beginning but went down slowly when the laser intensity increased over some specific point respectively. GAP got the highest impulse coupling coefficient overall and aluminum got the lowest impulse coupling coefficient due to its high laser irradiation threshold. Specific impulse of aluminum were at the range from 3000s to 9500s while GAP and PTFE as polymer got the same performance at 600s~800s mostly. The ablation efficiency of three working materials differ a lot that GAP is around 120% in maximum and aluminum is around 60%. PTFE’s ablation efficiency is around 10%.