NASA X-43A SCRAMJET Wood Model Airplane

A winged booster rocket with the X-43 itself at the tip, called a "stack", is launched from a carrier plane. After the booster rocket (a modified first stage of the Pegasus rocket) brings the stack to the target speed and altitude, it is discarded, and the X-43 flies free using its own engine, a scramjet.

The initial version, the X-43A, was designed to operate at speeds greater than Mach 7, about 8,050 km/h at altitudes of 30,000 m or more. The X-43A is a single-use vehicle and is designed to crash into the ocean without recovery. Three of them have been built: the first was destroyed; the other two have successfully flown, with the scramjet operating for approximately 10 seconds, followed by a 10 minute glide and intentional crash.

The first flight in June 2001 failed when the stack spun out of control about 11 seconds after the drop from the B-52 carrier plane. It was destroyed by the Range Safety Officer, and it crashed into the Pacific Ocean. NASA attributed the crash to several inaccuracies in data modeling for this test, which led to an inadequate control system for the particular Pegasus used.

The X-43A's successful second flight made it the fastest free flying air-breathing aircraft in the world, though it was preceded by an Australian HyShot as the first operating scramjet engine flight. While still attached to its launching missile, the HyShot flew in descending powered flight in 2002.

The third flight of the X-43A set a new speed record of 12,144 km/h (7,546 mph), or Mach 9.8, on November 16, 2004. It was boosted by a modified Pegasus rocket which was launched from a B-52 at 13,157 meters (43,166 ft). After a free flight where the scramjet operated for about 10 seconds, the craft made a planned crash into the Pacific Ocean off the coast of southern California.

The most recent success in the X-plane series of aircraft until it was replaced by the X-51, the X-43 was part of NASA's Hyper-X program, involving the American space agency and contractors such as Boeing, MicroCraft Inc, Orbital Sciences Corporation and General Applied Science Laboratory (GASL). MicroCraft Inc., now known as ATK GASL, built the X-43A and its engine.

The Hyper-X Phase I is a NASA Aeronautics and Space Technology Enterprise program being conducted jointly by the Langley Research Center, Hampton, Virginia, and the Dryden Flight Research Center, Edwards, California. Langley is the lead center and is responsible for hypersonic technology development. Dryden is responsible for flight research.

Phase I was a seven-year, approximately $230 million, program to flight-validate scramjet propulsion, hypersonic aerodynamics and design methods.