Measurement of air ionization behind intense shock waves

Ionization is measured in a quasisteady flow behind intense shock waves moving at 4.3-16 km/sec with the aid of a new method for measuring ion densities, in which thin disposable electrostatic probes are used. Test measurements of the electron density were carried out by using microwave techniques at shock-wave velocities 5-7 km/sec and by recording the Stark broadening of the 486.10-nm H-beta line for velocities 10-15 km/sec. The experimental findings confirm that local thermodynamic equilibrium breaks down behind intense shock waves at velocities above 9 km/sec when small probes are used and the initial pressures are low.