- 6,755 mile(s) per hour
- United States ()
The fastest aircraft with an air-breathing engine is the NASA X-43, which reached a speed of Mach 9.68 at 109,440 ft (33,357 m), which works out to an airspeed of around 10,800 km/h (6,700 mph), on 16 November 2004. The test flight took place over the Pacific Ocean, with the craft launched from NASA's NB-52B mothership.
The X-43A was an uncrewed drone fitted with an experimental engine called a scramjet (supersonic combustion ramjet). Scramjet engines only work at hypersonic speeds because they rely on air rushing into the intake at extremely high speed. This air passed down a tapered duct, compressed to extreme pressures by the narrowing space, which it is mixed with fuel. This super-pressurized fuel-air mix spontaneously ignites as the duct opens out again towards the rear nozzle, expanding rapidly and driving the aircraft forward. This is the same basic principle as a conventional turbojet engine (compression, ignition, exhaust), but it operates without moving parts (there are no compressor fans and turbines).
The X-43 was 12 ft 4 in long. 5 ft wide, and 2 ft 2 in high (3.75 m x 1.52 m x 0.66 m). It had a mass of around 3,000 lb (1,360 kg). To accelerate the drone to the hypersonic speeds needed to test the engine, the X-43 was mated to a Pegasus rocket booster, which brought it up to speed before being jettisoned.
On its record setting flight, the X-43's scramjet was only actually running for about 10 seconds, which was followed by a 9 min 45 sec glide to a crash landing somewhere in the Pacific Ocean near Guam some 620 km (385 mi) from its ignition point.