| As a new concept propulsion technology, laser propulsion is believed to have many advantages in the domain of astronautics. At present, it would cost more than 20 thousand dollars to send one kilogram effective load to outer space by a chemical rocket. But actually, the effective load only received about 66,000 kilojoules, which is equivalent to 18 kilowatt hours. The reason is that 99% of the rocket's mass is filled with the propellant and combustion system, and the effective load only takes a small amount. Correspondingly, the laser thruster can use the ground based laser as the energy supplier, so its effective load would take a much more proportion. Also, for the high temperature produced by focusing the laser in one point, the specific impulse of the laser thruster would easily reach thousands seconds, whereas the largest specific impulse of a chemical rocket would be only about 500s. However, the detailed mechanism of laser propulsion has not been studied thoroughly. It is still studied in laboratory and has not been realized in the domain of astronautics.When used in practical application, laser thruster would encounter many different environments, especially the rarefied gas environment, which has never been deeply studied. In order to understand and master the principles and laws of laser propulsion, it is necessary to study the mechanism of laser propulsion thoroughly. By studying the characteristic of the flow field and its evolvement in different environments, the mechanism of thrust generation can be disclosed. This would be helpful for the configuration design of thruster.In this work, we have developed a numerical tool based on multidomain treatment to study the detailed flow field in laser propulsion. An equilibrium flow model is implemented for the high temperature gas. Also, a parallel three-dimension Direct Simulation Monte Carlo program is developed based on Bird's standard programs, and was used to simulate the flow field of thruster in rarefied gas environment. |
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