I should stop commenting on this "hypersonic, changing-course-in-mid-flight, all-kind-of-missile-defense-penetrating, no-one-else-has-it" missile that President Putin and his military keep telling us about. How many times can they sell this thing? Apparently, as long as the public buys it.
It's been two years since this whatever was first tested with much secrecy and fanfare. Information has been quite slow to come, but we do have something - this seems to be an old project of the NPO Mashinostoyeniya, which was tested on top of a UR-100NUTTH/SS-19 missile. It may have been tested with other missiles, Topol or Topol-M, but I would seriously doubt it - Yuri Solomonov, the chief designer of these two was quite scornful about this "hypersonic warhead".
What is it? I'm not really a rocket scientist, but if I would have to guess, I would probably say that this might be some kind of a hypersonic cruise missile. To make maneuvers it would have to be in atmosphere, so either the ballistic missile that launches it flies along a quite depressed trajectory or it re-enters earlier than a regular warhead and makes maneuvers during the re-entry part of the flight. Changing trajectory during the ballistic phase of the flight outside of the atmosphere would also be possible, but it would take a lot of fuel.
Which brings us to the real questions - would a "hypersonic maneuverable" system like this be technically possible? I guess, yes. Would it be practical? Not at all. All these maneuvers would impose significant cost in terms of weight. If I remember correctly, the Soviet Union experimented with maneuverable warheads for its ICBMs to improve their accuracy, but then abandoned the idea precisely for that reason - it's just not worth it. I'm sure it's the same with the current system - maneuverability (or whatever it is) might be a nice thing to have, but it would hardly justify the cost.
So, what is this "miracle weapon" good for? Impressing journalists and pundits would probably be it. Which, when you think of it, is all this weapon has to do.