Key Points and Summary – In 1967, USAF Major “Pete” Knight set a world speed record that remains “unbroken” 68 years later.
-Flying the X-15A-2 rocket plane (Flight 188), Knight reached an astonishing Mach 6.7 (5,140.7 mph).
X-15 from U.S. Air Force Museum Original Photo. Image Credit: National Security Journal.
X-15 USAF Museum Photo. Image Credit: National Security Journal.
-This “remarkable” achievement, which often gets “lost in the shuffle” of modern hypersonic buzz (like the Top Gun: Maverick SR-72), was part of a critical NASA/USAF research program.
-Knight, one of only 12 pilots in the program, also earned his astronaut wings by flying the X-15 to an altitude of over 280,500 feet. The X-15 program, though “tragic” (one pilot was killed), was foundational for the Apollo and Space Shuttle programs.
The X-15 and Major Pete Knight’s Incredible Mach 6.7 Story
Nowadays, there’s plenty of buzz about the potential for producing warplanes with hypersonic speed capabilities, i.e., Mach 5 (3,386.35 mph; 6,174.0 km/h; 3,333.69 knots) or above.
In the summer 2022 cinematic blockbuster “Top Gun 2: Maverick,” we saw a fictitious flight of the (still officially apocryphal) SR-72 “Darkstar,” which is also known as the “SOB” as in “Son of Blackbird” because it’s envisioned as the hypersonic direct successor to the iconic SR-71 Blackbird spy plane, which still holds the world record as the fastest air-breathing aircraft ever built.
What tends to get lost in the shuffle of these current discussions is the fact that a whopping six decades ago, during the heady days of the Cold War, an American-made rocket plane already achieved speeds of Mach 6 or higher within the confines of the Earth’s atmosphere (as opposed to outer space).
National Security Journal now tells the remarkable story of the X-15 and its record-breaking pilot, then-U.S. Air Force Major (eventual retired Colonel) William “Pete” Knight.
William J. “Pete” Knight Mini-Bio
William John was born in Noblesville, Indiana, on November 18, 1929, to parents William T. Knight (1906–1968) and Mary Emma Knight (1909–1959). After graduating from high school, he attended Butler University and Purdue University and then enlisted in the U.S. Air Force in 1951.
From there, according to Col. (Ret.)’s official NASA bio page, “After receiving his commission through the aviation cadet program, he completed pilot training in 1953. Flying an F-89D for the 438th Fighter-Interceptor Squadron, he won the prestigious Allison Jet Trophy Race in September of 1954 [whilst still a mere 2nd Lieutenant]. After completing his undergraduate education with a degree in aeronautical engineering from the Air Force Institute of Technology [AFIT] in 1958, he attended the USAF Test Pilot School at Edwards AFB, where he graduated later that same year … In 1960, he was one of six test pilots selected to fly the X-20 Dyna-Soar, which was slated to become the first winged orbital space vehicle capable of lifting reentries and conventional landings. After the X-20 program was canceled in 1963, he completed the astronaut training curriculum at the new USAF Aerospace Research Pilot School at Edwards in 1964 and was selected to fly the X-15.”
(As a sidebar note, times sure have changed; nowadays, the Air Force, Navy, and Marine Corps alike all require a completed bachelor’s degree for eligibility for commissioning and flight training alike.)
X-15 Initial History
The rocket-powered X-15 was produced by the sadly now-defunct North American Aviation (NAA), an aerospace firm that had already gained fame during World War II via (1) the P-51D Mustang fighter plane that proved to be the game changer in the deadly skies over Western Europe and (2) the B-25 Mitchell medium bomber immortalized by the Doolittle Raid on Tokyo in 1942.
It made its maiden flight on June 8, 1959, and was officially introduced on September 17, 1959.
X-15A from U.S. Air Force Museum. Image Credit: National Security Journal.
The plane was conceived as part of a hypersonic flight research program designed to test and investigate several aspects associated with piloted hypersonic flight.
Information gleaned from this program was eventually used in the development of the Mercury, Gemini, and Apollo piloted spaceflights, as well as in the Space Shuttle Program.
A total of three airframes were built, which flew a combined total of 199 flights—divvied amongst 12 pilots—before the plane was officially retired in December 1968. Tragically, one of those pilots lost his life whilst operating the aircraft.
X-15 Technical Specifications and Vital Stats
Crew: 1
Length: 50 ft (15.24 m)
Wingspan: 22 ft (6.71 m)
Height: 13 ft 8 in (4.21 m)
Empty weight: 13,000 lb. (5,897 kg)
Gross weight: 15 tons (13607.8 kg)
Powerplant: Thiokol 57,000-pound thrust liquid propellant rocket engine
Range: 280 mi (451 km)
Rate of climb: 60,000 ft/min
The X-15 and Maj. Knight Set the Still Unbroken Speed Record
It was on October 3, 1967, in the skies over Mud Lake, Nevada, that the plane & pilot pairing of the X-15 and Pete Knight roared their way into history’s record books. The tandem achieved a speed of Mach 6.7 (5,140.7 mph, 8.273.16 km/h, 4,467.15 knots), thus making them-Maj. Knight is the fastest flying pilot ever. Sixty-eight years later, this remains the highest speed ever recorded by a crewed, powered aircraft. Knight achieved this milestone at an altitude of 102,100 feet (31,120 meters), or 19.34 miles.
The specific plane flown for this mission was an X-15A-2, bearing AF Serial Number 56-6671. The mission was officially designated Flight 188
For good measure, according to the NASA bio, “During 16 flights in the rocketplane, Knight also became one of only five pilots to earn astronaut’s wings by flying an airplane in space when he climbed to 280,500 feet on October 17, 1967.”
Where Are They Now (Plane and Pilot, That Is)?
As luck would have it, AF Ser. No. 56-6671 is the only surviving specimen out of the three X-15s built that has been preserved for posterity, sitting proudly in the National Museum of the United States Air Force at Wright-Patterson AFB, in the vicinity of Dayton, Ohio.
After 32 years of honorable service and more than 6,000 hours of stick and rudder time in over 100 different aircraft, “Pete” Knight retired from the Air Force in 1982 at the rank of full colonel (pay grade O-6) and was inducted into the National Aviation Hall of Fame in 1988. In 1984, he was elected to the Palmdale, California, city council, and four years later became the city’s first elected mayor. In 1992, he was elected to serve in the California State Assembly, representing the 36th District. In 1996, he was elected as a State Senator, representing California’s 17th Senate District, a role he held until his death from leukemia on May 7, 2004. Col. (Ret.) William J. Knight was interred at Desert Lawn Memorial Park in Palmdale.
About the Author: Christian D. Orr, Defense Expert
Christian D. Orr is a Senior Defense Editor. He is a former Air Force Security Forces officer, Federal law enforcement officer, and private military contractor (with assignments worked in Iraq, the United Arab Emirates, Kosovo, Japan, Germany, and the Pentagon). Chris holds a B.A. in International Relations from the University of Southern California (USC) and an M.A. in Intelligence Studies (concentration in Terrorism Studies) from American Military University (AMU). He is also the author of the newly published book “Five Decades of a Fabulous Firearm: Celebrating the 50th Anniversary of the Beretta 92 Pistol Series.”
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