At some point in the next few weeks, a B-52H bomber will carry a missile high into the air and launch it at an unprecedented velocity toward its target, according to the U.S. Air Force. If everything goes according to plan, that missile will accelerate to more than five times the speed of sound before deploying a dummy second stage that will promptly "disintegrate" somewhere in the atmosphere. The missile, known as AGM-183A, is supposed to be the first hypersonic weapon — or Air-launched Rapid Response Weapon (ARRW) — in the U.S. arsenal. It should move so quickly through the...