The argument for a HYPERSONIC missile testing ban

China and the United States recently conducted development tests of hypersonic missiles, designed to travel many times the speed of sound and reach targets thousands of miles away in an hour or less. Both tests failed, showing that hypersonic propulsion and flight—which involve extreme airspeeds, temperatures, pressures, and stresses, along with compact airframes and low weight—remain unproven technologies, even after decades of development. Solutions to the technological challenges of hypersonic flight may soon be within reach, using…