Facts summary and sources
North American X-15: speed field: Mach 6.7 (Reported flight result). First flight: 1959.
This is a secondary compilation. A source-check date applies only to the listed claim, not to the whole page or its translation. A page update is not a source check.
Sources and check records
- NASA: X-15 Hypersonic Research Program — William “Pete” Knight reached Mach 6.7 and 4,520 mph on October 3, 1967. [Reported peak speed of a crewed rocket-powered research flight.] · Event date: 1967-10-03 · Source checked for this claim: 2026-10-07
- Existing reference link · Source-check date not recorded
- Wikipedia reference · Source-check date not recorded
✈️ Full Specifications
| Designation | X-15 |
| Manufacturer | North American Aviation |
| Country | 🇺🇸 United States |
| First flight | 1959 |
| Service Entry | 1959 |
| Retired | 1968 |
| Crew | 1 |
| Length | 15.45 m (50.7 ft) |
| Wingspan | 6.81 m (22.3 ft) |
| Height | 3.96 m (13 ft) |
| Empty Weight | 6,620 kg (14,597 lb) |
| Max Takeoff Weight | 25,460 kg (56,139 lb) |
| Max Speed (Mach) | 6.7 |
| Speed evidence basis | Reported flight result |
| Max Speed | 7,274 km/h |
| Service Ceiling | 108,000 m (354,348 ft) |
| Engine | 1 × Reaction Motors XLR99-RM-2 liquid-propellant rocket |
| Thrust (each) | Dry 250 kN |
| Production | 3 |
🌐 Operators
🔁 Variants
- X-15-1 — First airframe
- X-15-2 — Second airframe (later rebuilt as X-15A-2)
- X-15-3 — Third airframe (lost in 1967 with pilot Michael Adams)
⚔️ Armament
Overview
On October 3, 1967, William “Pete” Knight flew the rocket-powered X-15A-2 to Mach 6.7 (4,520 mph, about 7,274 km/h). NASA records this as a crewed aircraft research-flight result. It belongs in a different category from uncrewed air-breathing tests such as the X-43A and from spacecraft reentry speeds. NASA X-15 program history.
Explore the units with the Mach speed converter: km/h, mph and knots. Mach depends on local air temperature; a model conversion does not replace the documented flight result.
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.
Limitations & Challenges
The X-15 pushed the boundaries of human endurance and material science, but at significant risk. The aircraft experienced several near-fatal incidents: on November 9, 1962, pilot Jack McKay crash-landed X-15 #2 after an engine failure, suffering severe spinal injuries. On November 15, 1967, pilot Michael Adams was killed when X-15 #3 entered a hypersonic spin during re-entry and broke apart at approximately 60,000 feet — the program’s only fatality.
The rocket engine’s high fuel consumption required air launch from a B-52. NASA’s program history gives a typical release altitude of about 45,000 feet and a speed above 500 mph. The Inconel X skin, reaction controls and unpowered return supported research into heating, handling and reentry. NASA: Hypersonic Research at the Edge of Space.
Notable Records
- Crewed rocket-powered research-flight result: Mach 6.7 on October 3, 1967
- 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.
Frequently Asked Questions
How fast is the X-15?
NASA records Mach 6.7 (4,520 mph, about 7,274 km/h) for William “Pete” Knight’s X-15A-2 flight on October 3, 1967. This is a crewed, rocket-powered aircraft result; it should not be mixed with spacecraft reentry speeds. NASA program history.
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.
References & Sources
- Wikipedia — North American X-15
- NASA — North American X-15
- Smithsonian Air & Space Museum — North American X-15