Gasdynamic processes of proposed laser pulse propulsion devices

The pulse laser propulsion engine works as follows: if a laser beam is focused in a gas or at a solid surface, rapid heating and ionization of the gas (optical breakdown) take place; if this occurs near the apex of a nozzle, the resulting plasma absorbs the laser radiation and acts like an explosion pushing the gas into external space causing a pulsed thrust. This paper presents an investigation of the physics of shock-wave propagation caused by laser explosion. One of the features of the phenomenon is the high temperature in the breakdown zone. A method of numerical solution of the radiation gasdynamic equations is developed and the calculations for different energies and nozzle parameters are made. These calculations lead to a conclusion about values of pressure and mechanical impulses, energy losses by radiation, and the character of the radiation spectrum. By means of a two-dimensional gasdynamic computation code, a spatial picture of the gas flow after the exit of the shock wave from a nozzle is revealed. Experimental studies of a number of small explosions in air are reported. The experimental values of a total mechanical impulse caused by CO2 laser irradiation of targets in air are found, and the total energy radiated out of the explosion zone is measured. The theoretical predictions are compared with experimental data.