Blackout analysis of small cone-shaped reentry vehicles

The high temperatures associated with the hypersonic reentry process lead to an increase in the collisions between molecules, which may result in the disruption of the electronic structure, producing free electrons and ions. This production of free electrons and ions creates a plasma or ionized flowfield around the vehicle that is known to degrade the quality of radio-wave signal propagation, leading to a loss of communication or "blackout." This study involves performing hypersonic computational fluid dynamics simulations in the commercial software CFD++ with a bluntnosed cone geometry at different flight conditions to predict how and when ground communication can be achieved to aid in the design of an alert transmitter, which is an extension of aircraft collision-avoidance system technology. Computational results show that a small blunt-nosed cone geometry has decreased ionization regions as the cone angle decreases due to a shifting of the reaction zone further downstream. As a result, higher freestream velocities have less of an impact in determining the location for an antenna, and communicating along the stagnation line is seen to be independent of cone angle.