The U.S. military requires new, high-agility interceptors and a layer of space-based sensors to defend against hypersonic threats, the presumed next defense secretary told lawmakers today, shedding new light on Defense Department thinking about elements of a hypersonic defense system. Army Secretary Mark Esper outlined for the Senate Armed Services Committee his views on defending against Russian and Chinese plans to field hypersonic boost-glide vehicles in the 2020s, ultrafast weapons designed to fly at speeds five times the speed of...