Just to be clear, space vehicles are not "hypersonic". They travel these speeds outside of substantial atmosphere, where the speed of sound is undefined. Mach n

Just to be clear, space vehicles are not "hypersonic". They travel these speeds outside of substantial atmosphere, where the speed of sound is undefined. Mach number is relative to local air conditions, ergo their Mach number isn't 25. It's undefined. Mach Number is a meaningless quantity. It's not accurate to say that a space vehicle travels Mach 25, only that it's speed is 25 times higher than the speed of sound at sea-level conditions. Saying this can be a useful reference to give context to the insane speed of orbital vehicles (as was done by the commenter above you). I say all this to give context about the surge in hypersonic research in recent years as being something distinctly different than achievements made in space-vehicles. It's not really accurate to say it's been given the "buzzword" treatment simply because things in space already move so fast. There's a distinct advantage (particularly for military objectives) to flying above Mach 5 in the atmosphere.