The term “hypersonic” typically refers to systems capable of traveling in excess of five times the speed of sound (Mach 5), a convention also adopted by the Chinese military. In more familiar terms, this corresponds to a speed of about 3,836 mph (6,174 kph) at sea level, under “average” atmospheric conditions.
Hypersonic systems can be manned, like the U.S. X-15 rocket-powered aircraft tested in the 1960s, or unmanned. It should be noted that spacecraft reentering the atmosphere and all ballistic missiles with ranges greater than about 300 km fly at hypersonic speeds for at least portions of their flight. This study is primarily concerned with next-generation weapon systems being developed by China that maintain hypersonic speeds for extended periods and have a high degree of maneuverability at those speeds. The physics involved in such high-speed maneuverability present major challenges in areas such as computer modeling, material sciences, and control mechanisms. It is worth bearing in mind, however, that although the focus of research in China in recent years has been on maneuverable ballistic missile warheads and hypersonic cruise missiles that can defeat contemporary antimissile defense systems, historically hypersonic flight research and development (R&D) has encompassed a much broader range of applications, including manned and unmanned reconnaissance, interceptor, and bomber aircraft, as well as civilian applications. Thus, the technologies that emerge from the current hypersonic weapons programs could have far-reaching ramifications for the Chinese aerospace industry across many sub-sectors.
While considered a cutting-edge technology, conceptually, controlled hypersonic flight has been a subject of study in the United States and the Soviet Union/Russian Federation since the 1950s. Practical applications of the technology have been under development since at least the 1960s.
For the United States, concerted study of hypersonic systems appears to have initially focused on reconnaissance. Only five years after Gary Powers’ U-2 spy plane was shot down over the Soviet Union, a planning document for reconnaissance noted that the U-2 was obsolete and that Soviet advances in surface-to-air missiles (SAMs) threatened the A-12 reconnaissance aircraft (SR-71, OXCART). Drones (many of which were downed over Vietnam and China) were perceived as having high vulnerability and limited utility. As a result, hypersonic gliders and powered aerial vehicles were developed by the CIA under the codenames ISINGLASS and ISINGLASS II. As one report put it regarding an early stage of R&D, “The interest is in a boost glide vehicle, air launched from a carrier no larger than a B-52, and capable of a trajectory of 6,000 nautical miles or more.” While eventually canceled, these efforts pioneered an engineering paradigm that all subsequent hypersonic systems have essentially followed.
The emergence and rapid development of China’s current hypersonic weapons program appears to have been driven by the shifting strategic balance and technological advancement of its neighbors and the United States. China is now pursuing hypersonic technology on a number of fronts with clear objectives. Militarily, hypersonics fit into a broader arc of China’s systematic development of strategic weapons.