In its fourth and final test, the X-51A WaveRider pulled off three and a half minutes of flight under the power of its supersonic combustion ramjet (Scramjet), the longest such flight ever. The WaveRider, developed by Boeing, DARPA, and the Air Force, is designed to test the feasibility of Scramjet-powered flight. A Scramjet utilized the atmosphere's oxygen, the air compression from its own forward motion, and less fuel than a traditional rocket to propel a craft to hypersonic speeds — in this case Mach 5.1. It's called the "WaveRider" because part of the reason it's able to stay aloft is that it literally rides its own shockwaves.
The last test of the X-51 didn't go so well, crashing down early into the Pacific after just 15 seconds. This time around, the test went smoothly. "That vehicle flew like a bat out of hell," said Joe Vogel, Boeing's program manager for the X-51 project. Under its initial, more traditional rocket power and then its Scramjet power, the X-51A flew for around six minutes and 230 nautical miles.
Now that the initial battery of tests is over, the goal is to take the telemetry and other data acquired during the flights to prepare the next generation of Scramjet vehicles — most likely to be yet more missiles. "The successes of the X-51A will pay dividends to the High Speed Strike Weapon program currently in its early formation phase with [the Air Force Research Laboratory]," the Air Force's press release touted. Boeing was equally proud of the test, producing the video below.