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GAO-19-705SP 1 (2019-09-16)

handle is hein.gao/gaobadzze0001 and id is 1 raw text is: Science, Technology Assessment, G A O Iand Analytics SCIENCE & TECH SPOTLIGHT: HYPERSONIC WEAPONS What is it? Hypersonic weapons fly at least Mach 5 - five times the speed of sound, or approximately 3,800 mph. Unlike ballistic missiles, which can reach similar speeds but have a relatively fixed flight path, hypersonic weapons, once developed, would fly at lower altitudes, be highly maneuverable, and may be able to change targets during flight. This will make them extremely difficult to defend against. How does it work? Most hypersonic weapons fall into two categories, hypersonic glide vehicles (HGVs) and hypersonic cruise missiles (HCMs). -Impact ross range Down range Source: GAO. I GAO-19-705SP An RV follows a parabolic trajectory determined mainly by its launch characteristics, its target, and gravity. An HGV can take a variety of trajectories and leave its final destination ambiguous. HGVs are unpowered and glide to their targets from a high altitude after initial launch by a rocket. They are expected to fly at altitudes between 25 and 60 miles. HCMs are powered by high-speed engines during their entire flight. They are expected to fly at altitudes between 12 and 19 miles. For most HCMs, a rocket would accelerate the missile to Mach 3 or 4, and then the HCM's own ramjet or supersonic combustion ramjet (scramjet) engine would take over. A ramjet uses the speed of the vehicle to ram and compress air with fuel, which is burned to produce thrust. A scramjet is similar, with air moving at supersonic speed. Source GAO. I GAO-19 705SP The air enters the inlet at a speed greater than Mach 1. It is then compressed by the engine geometry, and combustion occurs at supersonic speeds. How mature is it? According to a U.S. Air Force Scientific Advisory Board report, domestically, the core technologies needed for the development of a tactical range HGV have reached Technology Readiness Level (TRL) 5 out of 9. The board expected the remaining subsystems for such a weapon to reach TRL 6 or higher by 2020. According to GAO best practices, TRL 7 is the level of technology maturity that constitutes a low risk for starting system development. It indicates that a technology has achieved form, fit, and function, and has been demonstrated in an operational environment. Penetrate defenses. Hypersonic weapons would likely enable U.S. warfighters to penetrate existing adversary anti-aircraft and anti-missile systems because of their speed, maneuverability, and altitude (above typical anti-aircraft defenses and below interception points for ballistic reentry vehicles). Strike fleeting targets. The speed of hypersonic weapons would allow them to hit targets that are only vulnerable for a limited time, such as mobile, high-value military targets and adversary weapons systems. Agile targeting. A traditional missile needs to be launched with a target in mind, but a hypersonic weapon could be maneuvered later in flight. This could provide U.S. decision-makers more time and make it extremely difficult for adversaries to prepare. High travel speeds. Piloted hypersonic vehicles would allow for very short travel times and may have commercial applications. Such vehicles have essentially been limited to certain spacecraft reentering the atmosphere and experimental aircraft. GAO-19-705SP Hypersonic Weapons

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