The first X-51A WaveRider, complete with its rocket booster and scramjet engine, has arrived at Boeing's Huntington Beach, Calif., plant for structural testing leading up to a first flight attempt late this year.
This is the "Stacked Test Vehicle", or STV, and is being used for ground testing of the complete stack - the modified ATACMS missile booster at the back, in white, and the X-51A cruiser at the front, unpainted. The thing looks pretty small on its trolley - but the hopes of the hypersonic community ride of the success of this vehicle.
The X-51 can trace its roots all the way back to the X-30 National Aero-Space Plane, and its cancellation in 1993. The U.S. Air Force continued work on the two-dimensional scramjet flowpath through a series of ground demonstrator engines till it arrived at the Pratt & Whitney Rocketdyne SJY61 fuel-cooled, hydrocarbon-fuelled, dual-mode ramjet/scramjet that will power the X-51A. That's it, just visible under the cruiser:
The X-51A is tiny compared to the X-30, but if it flies successfully it will be a huge boost for hypersonics, and could find near-term application in a high-speed strike missile. The first flight attempt is planned for late October, with the stack to be dropped from a B-52 over the Pacific and boosted to around Mach 4.5, where the cruiser will separate, ignite its scramjet and accelerate to beyond Mach 6, staying there for about 250 seconds before its JP-7 fuel is exhausted and it plunges into the ocean.