✈️ Aircraft Specifications
| Designation | X-15 |
| Manufacturer | North American Aviation |
| Country of Origin | United States |
| First Flight | 1959 |
| Length | 15.45 m (50.7 ft) |
| Max Speed (Mach) | 6.7 |
| Max Speed (km/h) | 7,274 km/h |
| Service Ceiling | 108,000 m (354,348 ft) |
| Engine | XLR99 rocket engine |
| Crew | 1 |
| Status | Retired |
Overview
The X-15 remains the fastest crewed aircraft ever built, reaching a staggering Mach 6.7 (7,274 km/h) on October 3, 1967, piloted by William J. Knight. This hypersonic rocket-powered aircraft pushed the boundaries of human flight to the edge of space itself.
Design & Development
Built with an Inconel X nickel alloy skin to withstand temperatures exceeding 1,200°F during hypersonic flight, the X-15 was a marvel of engineering. Its XLR99 throttleable rocket engine produced 57,000 lbf of thrust. The aircraft used reaction control thrusters for attitude control at extreme altitudes where aerodynamic surfaces were ineffective.
Operational History
Over 199 flights from 1959 to 1968, the X-15 set numerous speed and altitude records. It reached 107.8 km altitude—well above the Kármán line defining the edge of space. Eight pilots earned astronaut wings flying the X-15. The program contributed critical data to the development of the Space Shuttle and all subsequent hypersonic research.
Notable Records
- Speed record: Mach 6.7 (still unbroken for crewed aircraft)
- Altitude record: 107,960 meters
- First aircraft to use reaction controls for space-like maneuvering
Armament & Weapons
The X-15 was a research vehicle and carried no weapons. It was equipped with extensive instrumentation for measuring aerodynamic heating, structural loads, and control effectiveness at hypersonic speeds. A ball nose sensor measured airflow angles, and the aircraft carried multiple cameras and data recorders.
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Frequently Asked Questions
How fast is the X-15?
The X-15 reached Mach 6.7 (4,520 mph / 7,274 km/h), making it the fastest crewed aircraft ever flown. This record was set by William “Pete” Knight on October 3, 1967.
Did the X-15 go to space?
Yes. The X-15 reached a maximum altitude of 354,200 feet (67.08 miles / 107.96 km), exceeding the Kármán line. Several X-15 pilots earned astronaut wings.
How many X-15 aircraft were built?
Three X-15 aircraft were built by North American Aviation. The program completed 199 flights between 1959 and 1968.
Is the X-15 still in service?
No. The X-15 was a research aircraft operated jointly by NASA and the USAF from 1959 to 1968. It contributed invaluable data to the Space Shuttle program.