Hypersonic Missiles

Why the Hype Around Hypersonics?
Sabbine Hossenfelder

Sabbine is my new favorite YouTuber. I watched one about the 5th Element, er, the 5th Force earlier, and it was fine. She has a blog (BackReAction) where she posts her videos along with transcripts. Most of the videos are her talking, but she does include some graphics that help illustrate the topic. This video includes a clip of a double sonic boom from a Concorde. I had to play it a couple of times in order to hear it. It's really quick, the two booms are like a tenth of second apart. Bang bang.

This is the first explanation of hypersonic missiles that actually explains anything. All of the rest have been nothing burgers. 

The bit about how long it takes a ballistic missile to reach its target versus a hypersonic missile is not complete. If the two devices are traveling the same distance across the Earth, then what she says is true, hypersonic missiles would take just as long as a ballistic missile. However, ballistic missiles are big and difficult to transport, so mostly they don't leave their home country unless they are on a submarine. Hypersonic missiles are smaller (they don't have to carry an oxidizer, which is roughly half of their fuel load, which is what makes up the bulk of the missile), so they could be carried by an aircraft and launched from a relatively short distance away.

Assuming, or course, that they actually make these things work. And then there's the whole hypersonic glider thing. Traveling at Mach 5 you are covering one mile per second. Turn off the engine / run out of fuel and you will glide for a bit, but I would be surprised if you could glide ten miles before you fell to the ground. I haven't heard anything about this.

Previous mentions of hypersonic (3).

Previous mentions of supersonic (many).