Defense Advanced Research Project Agency (DARPA), Boeing Integrated Defense Systems, Pratt & Whitney Rocketdyne and NASA have developed unmanned scramjet Boeing X-51A (also known as X-51A WaveRider) and it is used in tests to achieve hypersonic speed (a velocity of at least five times that of sound in the same medium under the same conditions). However, on this May 1, X-51A WaveRider achieved a speed of over Mach 5 (equivalent to around 6,200 kmph speed at sea level and 5,300 kmph speed at high altitudes) and made a longest duration hypersonic flight.
X-51A WaveRider completed its first powered hypersonic flight on May 26, 2010. Later, X-51A WaveRider made two more test flights, but both went fail. However, on May 1 of this year, 25-foot long and 4,000-pound weighs X-51A WaveRider made its fourth test flight. It was carried in the air by a U.S. Air Force plane B-52 to an altitude of about 50,000 feet (15 km; 9.5 mi) and then released over the Pacific Ocean.
Within moments, the scramjet first gained a speed of about Mach 4.8 and few moments later, it reached a speed of over Mach 5. Note that, at Mach 5 speed, the unmanned scramjet was supposed to melt, but miraculously, it hovered proudly in air for more than 3 minutes, the longest duration hypersonic flight until now. Here’s the fourth test flight of X-51A WaveRider that made a record.
Source: Air Force Technology