WASHINGTON—The Pentagon successfully tested a booster rocket motor on Thursday designed to power a launch vehicle carrying a hypersonic weapon aloft, the Navy said. The United States and its global rivals have intensified their drive to build hypersonic weapons—the next generation of arms that rob adversaries of reaction time and traditional defeat mechanisms. Defense contractors hope to capitalize as they make the weapons and develop new detection and defeat mechanisms. This week, the top U.S. military officer confirmed a Chinese hypersonic weapons test that military experts say appears to show Beijing’s pursuit of an Earth-orbiting system designed to evade American missile defenses. “We are on schedule for the upcoming flight test of the full common hypersonic missile,” said Vice Admiral Johnny Wolfe Jr, Director, Navy’s Strategic Systems Programs, lead designer on the program. That flight test, of the combined boost rocket and hypersonic weapon, is slated to happen before autumn …