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"Highlights from the second test flight of the X-43A hypersonic aircraft."

see also: X-43 3rd test flight (to Mach 10)

Public domain film from NASA, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

The X-43 is an unmanned experimental hypersonic aircraft with multiple planned scale variations meant to test various aspects of hypersonic flight. It was part of NASA's Hyper-X program and has set several airspeed records for jet-propelled aircraft. The X-43 is the fastest aircraft on record at approx. 7000 miles per hour (10,461 km/h).

A winged booster rocket with the X-43 placed on top, called a "stack", is drop launched from a larger 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, e 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 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 rocket used.

The X-43A's second flight was successful when it became the fastest free flying air-breathing aircraft in the world.

The third flight of the X-43A set a new speed record of 10,617 km/h (6,598 mph), or Mach 9.65 at 33,528 meters (110,000 ft), on November 16, 2004. It was boosted by a modified Pegasus rocket which was launched from a B-52 mother ship at an altitude of 13,157 meters (43,166 ft). After 10 seconds of free flight, the spacecraft made a planned crash into the Pacific Ocean off the coast of southern California.

This X-plane series of aircraft was replaced by the X-51. The X-43 was part of NASA's Hyper-X program…

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.

The X-43A aircraft was a small unpiloted test vehicle measuring just over 3.7 m in length. The vehicle was a lifting body design, where the body of the aircraft provides a significant amount of lift for flight, rather than relying on wings. The aircraft weighed roughly 3,000 pounds (about 1,300 kilograms). The X-43A was designed to be fully controllable in high-speed flight, even when gliding without propulsion. However, the aircraft was not designed to land and be recovered. Test vehicles crashed into the Pacific Ocean when the test was over.

Traveling at Mach speeds produces a lot of heat due to the compression shock waves involved in supersonic drag. At high Mach speeds, heat can become so intense that metal portions of the airframe melt. The X-43A compensated for this by cycling water behind the engine cowl and sidewall leading edges, cooling those surfaces…


The craft was created to develop and test a supersonic-combustion ramjet, or "scramjet" engine, an engine variation where external combustion takes place within air that is flowing at supersonic speeds. The X-43A's developers designed the aircraft's airframe to be part of the propulsion system: the forebody is a part of the intake airflow, while the aft section functions as an exhaust nozzle.

The engine of the X-43A was primarily fueled with hydrogen. In the successful test, about two pounds (or roughly one kilogram) of the fuel was used. Unlike rockets, scramjet-powered vehicles do not carry oxygen on board for fueling the engine. Removing the need to carry oxygen significantly reduces the vehicle's size and weight. In the future, such lighter vehicles could bring heavier payloads into space or carry payloads of the same weight much more efficiently.

Scramjets only operate at speeds in the range of Mach 4.5 or higher, so rockets or other jet engines are required to initially boost scramjet-powered aircraft to this base velocity.