SUMMARY
Communication blackout generally occurs during the re-entry at high velocities through the atmosphere. Air ahead of the re-entry vehicle dissociates and then ionises, leading to the production of electrons. These electrons may reflect or attenuate the communication signals. Electron densities with plasma frequency exceeding the communication frequency lead to blackout. Electron density is a function of the body shape, velocity and altitude. The viscous shock layer method is used to predict the electron density, and thereby the plasma frequency for various configurations. This method is successfully implemented for analytic and non-analytic geometry configurations available in the literature. The electron densities computed for the RAM-C configuration agree well with the flight results. The onset of blackout during the re-entry phase is also predicted reasonably well by this method. The method performs well at high altitudes, where nonequilibrium conditions prevail.Defence Science Journal, 2011, 61(4), pp.364-369, DOI:http://dx.doi.org/10.14429/dsj.61.1089