Fumio Takakusagi

Experimental Study of Intense Radiation around Si-Based Heat-Resistant Materials in Air Plasma Freejets

When a spacecraft enters the Earth’s or outer planet’s atmosphere at a hypervelocity, an extremely strong shock wave is formed over the spacecraft. In general, the aerodynamic heating from such a flowfield to the spacecraft is caused by the transport phenomena. Usually, the heating is so severe that heat protection by an ablation method is required.

Temperature measurements of atmospheric Ar plasma freejets by means of the Moire-Schlieren and spectroscopic methods.

The atmospheric Ar plasma freejets, generated by an electric arc discharge, are visualized and measured by the Moire-Schlieren method to obtain the details of their high temperature fields. Electron temperatures and electron number densities are also deduced from a combined method of the absolute intensity measurements of Ar spectral lines and the collisional-radiative process theory. From the experiments performed under the conditions of arc currents of 100-200 A and nozzle diameters of 3-4 mm, the following are found : (i) The gas temperatures are 1000-5000 K and the electron temperatures are about 8500 K. (ii) The distributions of gas temperature for the conditions show a similar form. (iii) The freejets are thermally in nonequilibrium, though the plasmas are fairly dense.