For years now, North Korea has been sporadically testing ballistic missiles as part of a relentless push to develop nuclear weapons capable of striking the continental U.S., and indeed most any location on the planet.

But since last fall, Pyongyang has also been launching new types of ballistic missiles that push the envelope not so much with regard to range or reliability or survivability, but in terms of flight path and detectability. These are the much heralded but frequently misunderstood hypersonic missiles that have generated headlines and alarm the world over.

The term hypersonic