On its fourth and final flight, the X-51A Waverider made history last week: the longest flight ever for an air-breathing scramjet engine.
An Air Force B-52 dropped the unmanned test vehicle from about 50,000 feet over the ocean off southern California, after which it flew more than 230 nautical miles in about six minutes. Top speed: Mach 5.1.
The Air Force has no immediate plans for follow-on tests. But in this Boeing promotional video, Joseph Vogel, the company’s director of hypersonics, explains the technology’s promise: