Nuclear weapon use is no longer warranted and big nation/states like the US, Russia and China will definately not be using them for any kind of attacks. This Mach-20 glider is for a more targeted attack. A similar concept is presented in "The Gold Coast" by Robinson, where a hypersonic glider tracks and destroys target using only kinetic energy (no explosives). This also allows you to hit targets in high-density (ie. urban) environments without affecting the surrounding area.