Some of the aerodynamic problems that arise in flight at hypersonic speeds can be studied experimentally with wind tunnels and measuring techniques that do not differ in principle from those used for research on supersonic flow. If, however, it is required to simulate the very high temperatures of hypersonic flight, it is usually necessary to use heaters and tunnels of unconventional design, frequently having a very short running time, or to make tests with a model launched or propelled at high velocity.
The short running times sometimes involve the use of measuring techniques that differ considerably from those of conventional wind tunnel practice. Also, in the presence of high temperature, real gas effects, it is sometimes necessary to measure additional quantities in order to define the state of the gas. The paper contains a brief introductory review of these topics, and of the extent to which experimental test facilities can reproduce the conditions of full-scale hypersonic flight.