Source: www.spacedaily.com
"Only days after Guinness World Records certified the prior flight of NASA's X-43A hypersonic technology demonstrator aircraft as a world speed record, a full-scale dress rehearsal for the last and even faster flight of the small unpiloted research aircraft is tentatively scheduled to occur on Tuesday, Sept. 7 from NASA's Dryden Flight Research Center.
The dress rehearsal, officially called a "captive carry" mission, will involve a full-up replication of all operational functions that will occur on the actual research flight later this fall.

In this captive carry mission, however, the X-43A and its modified first-stage Pegasus launch rocket will not be launched from NASA's B-52B mother ship.

The X-43A is powered by a revolutionary supersonic-combustion ramjet or "scramjet" engine integrated into the airframe.

During its flight last March, the second X-43A maintained a speed of at least Mach 6.83, or almost seven times the speed of sound. For the final flight, the third vehicle is tentatively targeted to reach and maintain a speed of about Mach 10, or close to 7,200 mph.

Pending thorough evaluation of all captive-carry flight data, the test could lead to launch of the X-43A on its final flight in the Hyper-X hypersonic research program in late October."