Abstract:

Laser thruster will inevitably expose itself to inflow when flying in the atmosphere at a high altitude, and the inlet states will exert a direct influence on its propulsion performance because of their effects upon the steady flow field before laser ignition. A second order method is used to simulate the detailed evolving process of the inner and outer flow fields of an air breathing laser thruster model with a circular focusing for a free stream at Mach number 5 under three conditions: when the inlet was open, closed and ajar respectively. The results indicate that the wave drag is lowest when the inlet is open. When the inlet is closed for a long enough time, there is an obvious increase in the propagation velocity of the shock wave, which induces the maximal peak value of the rising positive thrust and counteracts the additional negative thrust brought  about by inlet closing. Impulse coupling coefficient is lowest and propulsion poorest when the inlet is ajar. Since propulsion performance may be improved greatly by improving the design of inlet configuration according to numerical calculation and analysis, much further work is required for its optimization in future.

Key words: laser propulsion, air-breathing mode, impulse coupling coefficient, inlet states, numerical simulation