Boeing's has released video of the successful fourth and final flight on May 1 of the Air Force Research Laboratory's X-51A WaveRider scramjet engine demonstrator.
Attached to its modified ATACMS booster, the X-51A cruiser was carried aloft under a B-52H and released at about 50,000ft over the Pacific. The booster accelerated the stack to Mach 4.8 in 26sec. The cruiser then separated and ignited its hydrocarbon-fueled scramjet engine. The fuel-cooled scramjet burned for 240sec, exhausting its fuel supply, then the vehicle coasted to a watery demise in the Pacific. In all, about 370sec of flight data was collected, during which time the cruiser traveled more than 230nm.
Of the four flights in the $300 million program, this was the first full success. The first flight in May 2010 was a partial success, the scramjet burning for more than 200sec and the vehicle reaching Mach 5 before a leaking nozzle seal caused it to lose control. The second flight ended early when an inlet unstart prevented the scramjet from igniting successfully. The third flight in April 2012 ended 15sec after the cruiser separated from the booster, after a control fin malfunction.