ABSTRACT
The most distinctive feature of a supersonic flow is shock waves. They were discovered theoretically by Rankine (1870) and Hugoniot (1877) over a century ago. Ernst Mach was the first to demonstrate their existence by publishing in the 1880s schlieren photographs of a bullet in supersonic flight. (See Van Dyke, 1982, for an enlargement of one of these photographs.) This remarkable picture shows the bow shock, recompression shock, and turbulent wake. Nevertheless, shock wave theory developed slowly until the end of World War II. At the time of the war, only the basic fundamentals were known; this material is usually covered in an undergraduate compressible flow course. After the war, the pace of discovery quickened, spurred on by interest in supersonic flight, nuclear explosions, and the reentry physics of long-range missiles.
