Introduction

Recent developments in rocket and missile technology have made possible hypersonic vehicles such as intercontinental ballistic missiles, satellites and space probes. During the entry of these hypersonic vehicles into the planetary atmospheres, numerous environmental problems in the areas of fluid dynamics and physics of high temperature gases are encountered. The equilibrium temperature in the stagnation region will be greater than 65ΟΟ Κ for flight Mach numbers exceeding 20. The air at these high temperatures can no longer be considered a simple mixture of nitrogen and oxygen molecules; instead, it will dissociate, ionize and experience chemical reactions between some of the constituents. Many of the conventional experimental tools for obtaining aerodynamic information, such as supersonic and hypersonic wind tunnels, have become inadequate for investigating the real-gas effects. In recent years many new experimental techniques were developed to simulate some of the extreme conditions encountered by the hypersonic vehicles. The capabilities and the results for some of these new facilities will be discussed in the following papers.