Technically, far-flying nuclear-tipped ballistic missiles that arc into space have already been traveling at hypersonic speed for over 60 years.  But conventional ballistic missiles remain highly visible on radar and f;y in a predictable trajectory, making them susceptible to advanced missile defense systems.  By contrast, today's hypersonic weapons attain hypersonic speeds flying in a much flatter trajectory, making them faster to reach theirr target, harder to detect, more maneuverable, and more difficult to shoot down.  The primary hypersonic paradigm is a "boost-glide" weapon which has two stages.  First, solid fuel rocket boosters launch the weapon to incredible speeds and altitudes, just as for an old-fashioned ballistic missile.  But instead of continuing on a predictable ballistic trajectory, the misssile releases an unpowered cone-shaped glide vehicle designed to skip above the atmosphere over great distances.  The glide vehicle is far more maneuverable than a ballistic missile, making it more precise and capable of dodging or entirely circumscribing air defenses.  We are talking MACH 20 or 4.2 miles per second.  A consensus seems to have emerged in the militaries of China, Russia and the United States that hypersonic weapons are poised to disrupt the future of both conventional and Nuclear warfare due to their ability to strike targets with incredible speed, precision and evasiveness.  Even Japan and The UK are pursuing HYPERSONIC WEAPONRY.                                                                                                   AIR-BREATHING HYPERSONIC DEVELOPMENT -  An alternative approach to hypersonic weaponry involves use of air-breathing scramjet or ramjet engine.  These both use the impact of incoming air to create compression for efficient high speed propulsion though slower (MACH 5-10), such weapons would be smaller, less complex and capable of staying near-maximum speed for longer than a glide vehicle-based weapon.  However, air-breathing or "aerobic" hypersonic weapons technology remains comparatively immature, though Russia has been testing an AIR-BREATHING ZIRCON HYPERSONIC ANTI-SHIP MISSILE since 2012.  The Missile Defense Agency has requisitioned $206.8 million dollars for 2021 to develop ANTI-HYPERSONIC CAPABILITIES, including satellite-based early warning capabilities and an Interceptor known as GLIDE BREAKER.    -    From Forbes -  Sebastien Roblin                                                                                                                                 A CONGRESSIONAL REPORT NOTES:  "Unlike China and Russia, The United States is not currently developing hypersonic weapons for use with a nuclear warhead".