On Guidance and Control for Hypersonic Weapons

The interest in hypersonic weapons has increased in recent years. Since countries like USA, Russia, China, and India claim to have hypersonic glide vehicle systems operational or well under way, the threat posed by this type of weapon must be considered. This report presents some possibilities and challenges regarding stability, control actuation, trajectory shaping, and guidance for hypersonic vehicles, with the purpose of supporting hypersonic weapon assessment. To stabilize and control hypersonic vehicles is a challenging task. With increasing Mach number, the control surface efficiency tends to decrease and undesired dynamic cross couplings that are difficult to predict may appear. Hypersonic vehicles can also reach altitudes where aerodynamic forces become negligible. Hence, other types of control actuation may be required. Reaction jets seem to be a suitable choice, but other technologies are also discussed in the report. Simplified methods are available for approximate estimation of aerodynamic forces and moments. Some phenomena not considered by these methods, that may have considerable influence, are described. Guidance algorithms for hypersonic glide vehicles have much in common with guidance for space vehicles. Traditionally, space launches and atmospheric reentry have involved precomputed trajectories. By iteratively computing guidance commands from updated target information, flexibility can be increased, which is desired for hypersonic weapons. This, however, requires more computational capacity onboard. The guidance algorithms need to be reliable, efficient, accurate, and provide trajectories that are guaranteed to be feasible.