Hypersonic Vehicles: State-of-the-Art and Potential Game Changers for Future Warfare

Abstract

Hypersonic flight is lacking a scientific definition, but is typically understood as flight within the atmosphere at speed around and beyond Mach 5. In this regime, dissociation of air starts to get significant and kinetic heating results in increasingly severe problems for a vehicle with increasing flight Mach number. Temperatures to be dealt with are about doubled between Mach 4 and 6 and quadrupled between Mach 4 and 9. Drag forces get huge and limit longer flight to altitudes within the stratosphere. Today, long duration flight at Mach numbers beyond 5 poses technological challenges with regard to structural materials and design, cooling and insulation, aerodynamics and flight control as well as propulsion by SCRAMJET (supersonic combustion ramjet), which are well beyond actual operational technologies; thus being a topic of various current research activities. Examples for hypersonic flight range from the X-15 experimental rocket plane of the 1960’s, various reentry capsules and experimental vehicles, the Space Shuttle and a number of newer experimental programs with the USAF X-51 (Figure 1) as a most recent one. Hypersonic research is conducted by nations with highly developed R&D capabilities and adequate financial resources including the US, Australia, Russia, China, Europe and India.