The achievable total enthalpy and the pressure level in a shock tunnel depend on its capability to generate strong shock waves. To produce a strong shock wave, high pressure and high sound speed are two key parameters for driver gases. There are various techniques to increase the driver gas sound speed, which are essentially different approaches in the way to raise the driver gas temperature. The first technique to increase the driver gas sound speed is by the use of a light gas, and the second one is by heating the light gas to a high temperature with gas heaters. The light-gas-heated shock tunnel is introduced in this chapter, and the electrical heaters are discussed in detail, including the relatively simple electrical resistance heaters and electric-arc heaters. Strictly speaking, the electric-arc heating is not a gasdynamic technique and it is not capable of completing flight-condition duplication for hypervelocity testing. However, it is selected because it can generate extremely high total enthalpies and is useful in certain applications.

In this chapter, the aerodynamic fundamentals for the working principles of shock tunnels are summarized. The moving waves, including expansion waves, shock waves, and contact surfaces, are introduced as the key issues and their theories are based on the unsteady one-dimensional flows in textbooks of aerodynamics. As unsteady one-dimensional moving waves are also critical for the design and operation of shock tunnels, their theories are also selected and summarized in this chapter for book completeness and readers’ convenience.

The detonation-driven shock tunnel is one of three important classes of hypersonic and high-enthalpy ground testing facilities that are based on the shock-heated principle. The theory and methods for developing the detonation-driven shock tunnels aiming at hypervelocity flow generation are summarized in this chapter. At first, the primary concepts for detonation drivers are presented to demonstrate their unique advantages for aerodynamic ground-based testing. The difficult problems arising from the development of hypervelocity shock tunnels for simulating flight conditions are identified and discussed in detail to address critical issues underlying the high-enthalpy shock tunnel design. Then, three kinds of detonation-driven shock tunnels are introduced, and their key techniques and performances are reviewed and discussed in detail. Finally, some experiments are summarized to demonstrate the capability of the detonation-driven hypersonic shock tunnel and the importance of the measurement techniques for hypersonic and high-temperature flow experiments. Both are the frontiers of high-enthalpy flow research for developing hypersonic vehicles.

In order to introduce hypersonic ground testing facilities, background information in hypersonics is presented to show to readers what we want to do, where we have been, and where we are going to go. These will provide with a good indication of the research needs that are called as hypersonic vehicle ground testing. It is of fundamental importance that a vehicle design must be carefully evaluated in ground test facilities before flight testing can proceed. Indeed, the development of hypersonic vehicles is related to the capability development of hypersonic ground testing facilities.