ABSTRACT
When a vehicle flies with hypersonic velocity or reenters the atmosphere, a strong bow shock is formed in front of the vehicle, which causes air to be heated. The temperature in a shock layer is high enough to dissociate the oxygen and nitrogen molecules of the air, which triggers complex chemical reactions, recombining these molecules and producing ionization. The vehicle is enveloped by a thin layer of dissociated plasma consisting of ions and electrons, which is called a plasma layer. The formed plasma layer engenders negative effects on a vehicle’s operation, particularly for its communication because of the high-electron number density. This communication difficulty is known as communication or radio blackout. This phenomenon was well known at the beginning of space exploration, but re-entry capsules continue to experience radio blackout during re-entry. This entry reviews previous approaches for radio blackout mitigation and evaluates them in terms of realistic application. One approach to solving the radio blackout problem would be to reduce the electron number density of the plasma layer around a vehicle. To manipulate electron number density, this entry introduces an innovative concept of plasma communication by using an electromagnetic, ExB layer.
