Plasma Sheaths of Models in Hot-Shot Wind Tunnels

The nitrogen flow characteristics around models is studied with a view to obtaining data which determine the physical state of the plasma. Among all possible techniques, the most adaptable to the special hot-shot conditions-electrostatic probes and VHF microwave reflectometry-is chosen. The experimental apparatus and results in nitrogen are described. The ionization is not homogenous during the shot; this result seems to confirm the assumption that the plasma flow is utilizable only after a delay of more than ten milliseconds following the shock formation period. The hot-shot utilization range is examined for this type of experiment.