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.

Status updates will be available on-line at at: http://www.nasa.gov/missions/research/x43-main.html. Still photos will be posted to the NASA Dryden web site photo gallery at http://www.dfrc.nasa.gov/Gallery/Photo/X-43A/index.html. Video footage will be available from the Dryden Public Affairs Office by calling (661) 276-3449.

The X-43A/Hyper-X hypersonic research program is a joint effort of NASA's Langley Research Center, Hampton, Va., and Dryden Flight Research Center, Edwards, Calif.