And there it is—Russia is now officially commissioning their new hypersonic weapon for service. They claim a top speed of Mach 27. If anyone had doubts, this likely solidifies that hypersonics will be a key defense issue for the foreseeable future. apnews.com/597e7f2b20b21a…
This is what’s called a “boost-glide” system. The vehicle is “boosted” to high altitude and velocity on top of a rocket, where it then separates from the booster and performs a controlled, high-speed, low-altitude “glide” to the target. It’s like riding a roller coaster. 
The problem for the US right now is that the glide portion is very difficult to track with long range radar (too low) and extremely difficult to intercept (too fast and maneuverable).
For those curious about the heating (we’re talking surface of the Sun temperatures at these Mach numbers), it’s definitely a design challenge. But Apollo reentry was M~36 and Shuttle/LEO reentry is M~25 so it’s manageable with ceramics and carbon composites, especially w/o crew.
While we’re here, I’ll just add my two cents that it’s a bit naive to simply dismiss this technology because we don’t want to believe Russia could pull it off. Is it really ready for prime time? I don’t know. But right now they take our astronauts to the ISS because we can’t.
We hear news of test flight failures and see that as weakness/ineptitude but in reality their engineers learn a great deal each flight. There’s simply a much higher tolerance for that sort of thing in their govt. And don’t forget China is working on this stuff too. It’s real.
Why does this technology matter when it’s already unlikely we could stop a nuclear volley? Who says this is limited to nuclear weapons? The breakthrough is in a rapid, global tactical strike capability where you could either project conventional force over a large region or...
have the ability to hit single strategic targets at long range, without warning, and with precision (which is the really hard part that almost certainly isn’t sorted out yet). It can expand operational range during a conflict—like having longer arms than the person you’re boxing.
