Comprehensive Research Of Laser Ablating Viscous Liquids

Content:Laser propulsion technology is a new-concept space propulsion technology which based on the separated energy source from the aircraft.The fundamental theory of laser propulsion technology,which appears great differences from traditional chemical propulsion,is to transform laser energy to aircraft's kinetic energy with intereaction between the pulse laser and working substance.Thus,laser propulsion has a higher specific impulse,lower cost and adjustable propulsion parameters.It can also overcome many disadvantages of chemical propulsion such as its low load ratio and large scale.Specific impulse and momentum coupling efficiency are two important parameters in laser propulsion.Solid working substance,which took up an important position in early research,has high specific impulse and low momentum coupling efficiency.However,later research shows that liquid working substance has low specific impulse and high momentum coupling efficiency.According to recent research,the propulsion characteristic of viscous liquid is between the solid and the liquid.This special property make it more possible to find practical working substance and ideal reaction condition.The main content of this paper is to reveal the relationship between viscous liquid's propulsion characteristic and its physical property by experimenting under various conditions and measuring specific impulse,momentum coupling efficiency and other relevant parameters of viscous liquids.A YAG laser device with wavelengths of 1064/532 nm is used in all the experiments.The first part is the research of carbon-doped glycerol.Wavelengths of both 1064 nm and 532 nm are used.The variation range of the pulse energy is from 50 to 100 mJ,while the variation range of carbon mass percentage is from 0 to 5%.Along with the energy increasing,momentum coupling efficiency decreases,but specific impulse increases,while with carbon mass percentage increasing,the two propulsion parameters decrease at the same time.The second part is the comparison of carbon-doped GAP and carbon-doped glycerol under 1064 nm pulse laser ablation.These experiments are based on higher mass percentage(0~30%)and larger variation range of the pulse energy(25~180 mJ).Results indicate that the propulsion characteristic of GAP is similar to that of glycerol,but carbon-doped GAP has a higher specific impulse than carbon-doped glycerol does.Compared with pure GAP,carbon-doped GAP has a higher specific impulse but a lower momentum coupling efficiency,in other words,carbon-doped The propulsion characteristic of GAP is close to that of solid.In summary,The doped solid material in the viscous liquid working substance could restrain the implicated sputtering and increase the specific impulse.With the energy density of 15 J/cm2,wavelength of 1064 nm,carbon mass percentage of 15%,the experiments acquire the momentum coupling coefficient of 220 N/W,the specific impulse of 900 s and the transformation efficiency of 100%.the coefficient is better than the reported experimental results of pure liquid GAP and solid carbon doped GAP.