Quantification of Hypersonic Missile Capabilities Using the Hypersonic Glide Vehicle Simulator: A User Manual

Introduction

In recent years, hypersonic weapons have garnered a great deal of interest and funding, particularly in the United States, Russia, and China.¹ These weapons are distinguished from other missile technologies by their ability to glide through the atmosphere at more than five times the speed of sound (Mach 5 or ~1.7 km/s) for substantial portions of their flight trajectories. Figure 1 illustrates a typical hypersonic missile trajectory. In its initial stage, this trajectory is identical to the launch of a ballistic missile, a type of weapon that has been widely deployed and used for decades. After brief acceleration by a rocket engine, however, a hypersonic missile trajectory diverges from that of a ballistic system, diving to lower altitudes within Earth’s atmosphere then gliding the remaining distance to the target. Hypersonic cruise missiles work in a similar fashion, yet they carry air breathing engines that provide thrust during the glide phase.² They typically fly at lower maximum speeds and altitudes than hypersonic boost-glide missiles.

Hypersonic missiles are subjected to aerodynamic drag as they glide through the atmosphere, which continually slows their flight.³ However, these aerodynamic forces also offer opportunities for extending missile range, if glide begins at the end of a long ballistic phase, and for midcourse maneuvering. Unlike a typical, long-range ballistic missile, which has little capacity to maneuver after the boost phase and therefore flies a largely predictable path to its target, a hypersonic missile can take advantage of aerodynamic forces to turn left or right and pitch up or down throughout its glide phase.⁴ This enhanced maneuverability comes at the cost of lower average flight velocity, longer flight time, and greater expense, relative to comparable ballistic missile designs.⁵ However, maneuverability could prove useful in certain missions, offering, for example, the potential to avoid overflight of a certain region or approach a target from an unexpected direction.

To date, most analyses in the open literature of the performance and global security implications of hypersonic weapons are of an abstract and speculative nature. Quantitative, mission-based technical assessment is rare, and that which is available⁶ often calls into question the common narrative of an impending hypersonic “revolution.”⁷

To better elucidate the roles that hypersonic missiles may play in the future of war, and to anticipate their impacts on global security, technical analysis of hypersonic weapon performance in specific missions is needed. Yet this analytical work is challenging, particularly for those without technical training. Policy analysts, political scientists, and journalists, for instance, may lack the skillset necessary for modeling missile flight, and may thus rely on technically unsupported narratives in assessing the implications of hypersonic weapon development and deployment. To lower these analytical barriers, we have developed the Hypersonic Glide Vehicle Simulator, a web application that facilitates fast and easy computation of hypersonic missile capabilities in a variety of militarily-relevant scenarios.⁸ This application makes use of computational models developed by Tracy and Wright that simulate the flight of hypersonic glide vehicles through Earth’s atmosphere.⁹