Herbert identified the solid fueled, kevlar-wrapped missile that North Korea showed off as the Pukgukgsong-3, or the third version of North Korea's submarine-launched missiles.
A nuclear-armed North Korea is scary, but if North Korea could arm even a few of its 60 or so submarines with nuclear missiles, even with the US's massive advantage in submarines and submarine hunting, it would present a likely unsolvable puzzle for the US military.
Additionally, missiles launched from submarines don't need to have ICBM ranges, as they can get close to a target. Regardless, Herbert said the new materials would probably boost the range of the missiles by 30 or 40 percent.