Radio Communication Through The Hypersonic Plasma Sheath

Hypersonic transatmospheric vehicles will become an important component of operations for the Air Force in the future. These new maneuvering aerospace vehicles will encounter many technology hurdles that were never faced by ballistic re-entry vehicles. The trajectory times will be thousands rather than tens of seconds and vehicles will not only descend (ballistically) but ascend and descend periodically during the extended flight times. Such changes will have profound effects on the vehicle performance, producing complex flowfields over three-dimensional surfaces that may either be laminar or turbulent or relaminarized. These scenarios have the potential of creating very complex electron density distributions over RF sensors during the hypersonic flight leading to plasma sheathing and the so-called "blackout problem" of reentry. In order to mitigate these undesirable effects, an innovative approach to plasma sheathing control is proposed. We will evaluate the reduction of the blackout problem in three unique ways: control boundary layer transition (BLT), inject additives into the boundary layer, and incorporate chemical species to scavenge electrons. In Phase I, these techniques will be evaluated using Physical Sciences Inc.'s reentry physics suite of codes and plasma sheathing methods will be designed. These designs will be fabricated and ground tested in Phase II.