In Pictures: Aircraft Used In The North American X-15 Hypersonic Program

*Neil Armstrong with the X-15 -1, one of the five aircraft of the X-15 program.*
*Photo: NASA | Wikimedia Commons*

The X-15 was the first aircraft to cross the boundaries of outer space. It was also the first airplane to reach hypersonic speed. Neil A. Armstrong, a NASA pilot and the first person to moon, has been documented at the contracted flight test program.

*The B-52 carrying the X-15 for a research flight on 13 April 1960 on Air Force Maj.*
*Photo: NASA | Wikimedia Commons*

A modified B-52 Strat fortress, a massive bomber, was used as its aerial launchpad and set to a height of 45,000 feet.

The X-15 flight crew, left to right: Air Force Captain Joseph H. Engle, Air Force Major Robert A. Rushworth, NASA pilot John B. “Jack” McKay, Air Force Major William J. “Pete” Knight, NASA pilot Milton O. Thompson, and NASA pilot Bill Dana.
Photo: NASA

NASA reported that the six pilots in the pictures above “made 125 of the 199 total flights in the X-15. Rushworth made 34 flights (the most of any X-15 pilot“.

*The fastest X-15 ever flown, the X-15-2*
*Photo: NASA | Wikimedia Commons*

The X-15-2 reached a maximum speed of Mach 6.72 (4,534 mph), making it the fastest aircraft of the X-15 series.

Types of aircraft used in the X-15 program

*Design of X-15 along with modifications-X-15A-2* *Photo: NASA*

The X-15 program primarily used single type of aircraft: the North American X-15 and the X-15A-2, a modified version of the second X-15 aircraft, was delivered to NASA in February 1964. As reported by NASA the X-15A-2 was modified with external fuel tanks and a 28-inch fuselage extension for liquid hydrogen.

The origins of the X-15

*Bell X-1, the high-speed experimental flight program was a joint effort of the Air Force and the National Advisory Committee for Aeronautics, the predecessor of NASA*
*Photo: NASA | Wikimedia Commons*

Air Force test pilot, Capt. Chuck Yeager piloted the Bell X-1 (shown in the picture above) over the desert at Muroc Dry Lake in California and flew the first aircraft to break the barrier of the speed of sound. The aircraft investigated aircraft behavior in transonic flight regime (between Mach 0.8 and about 1.3).

The Bell X-1A, investigated aerodynamic effects to a Mach number of 2.44. Photo: NASA | Wikimedia Commons

*A Pakistani Lockheed F-104A Starfighter (56-803)*
*Photo: Pakistan Air Force (PAF) | Wikimedia Commons*

The Lockheed F-104 Starfighter was the first aircraft designed for sustained cruise at Mach 2. The aircraft had wings with a leading edge so sharp that it merited a protective glove over it so as not to injure the ground personnel handling it. In comparison to the F-104, the X-15 had wider fuselage and thicker wing with blunt leading edges.

Left: Workers attach the WAC Corporal second stage to the V-2 booster for the Bumper 7 flight at Cape Canaveral, Florida. Middle: Bumper 8 in its gantry at Cape Canaveral prior to launch. Right: The first rocket launch from Cape Canaveral, the Bumper 8 flight.
*Photo: NASA*

Aa WAC Corporal rocket mounted on top of a captured German V-2 boost vehicle launched in 1949 became the first human-made object to reach hypersonic speed.

*The Bell X-2 (46-674) on the ramp at Edwards Air Force Base with the mothership B-50.*
*Photo: U.S. Air Force | Wikimedia Commons*

Bell X-2 was the second aircraft designed to investigate the aerodynamic effects to a Mach number of 3.2.

“A risk example is the X-15’s first flight. Launched at 33,550 feet and without an engine, which otherwise would allow the pilot to go around again if his approach was not right, the pilot had less than five minutes to learn how to handle the airplane in pitch, roll, and yaw, and to practice a simulated landing at altitude before doing the real thing. On this first flight, a longitudinal instability that caused the airplane to cycle up and down uncontrollably made it dangerously difficult to land.”

– X-15: The World’s Fastest Rocket Plane and the Pilots Who Ushered in the Space Age, by John Anderson and Richard Passman.

The five different aircraft used in the X-15 program

The X-15’s first flight was launched at an altitude of 33,550 feet and without an engine.

North American X-15-1

*The North American X-15 aircraft, ship #1*
*Photo: NASA | Wikimedia Commons*

Air Force Serial	56-6670
Number of Flights	81
Highest Speed Recorded	Mach 6.06 (Pilot Bob Rushworth)

*During its October 1958 rollout ceremony at the North American Aviation (NAA) facility in Los Angeles, NAA pilot A. Scott Crossfield poses in front of the X-15-1.*
*Photo: NASA*

The first unpowered glide flight of X-15-1 which took place on June 8 was piloted by NAA pilot A. Scott Crossfield. The flight lasted just five minutes.

*The photo on the right shows the flight unpowered glide flight of the X-15. The image of the right shows the actual flight.*
*Photo: NASA*

The high-speed record for the X-15-1 was set by Robert A. Rushworth on December 5, 1963, as he achieved a speed of Mach 6.06.

*Robert Rushworth, who piloted the X-15 thirty-four times in the cockpit of the aircraft.*
*Photo: NASA | Wikimedia Commons*

Some other accomplishments of Rushworth in the X-15 program included:

the first ventral-off flight on October 3, 1961
the highest dynamic pressure of 2,000 pounds per square foot

*The X-15-1 was later equipped with XLR99 engines.*
*Photo: loganrickert | Wikimedia Commons*

Pete Peterson achieved a speed of Mach 4.11 and an altitude of 78,000 feet with the X-15-1 equipped with the higher-thrust XLR99 engines.

*North American X-15 -1 at the National Air and Space Museum.*
*Photo: Mys 721tx | Wikimedia Commons*

North American X-15-2

Air Force Serial	56-6671
Number of Flights	53
Highest Speed Recorded	6.72 (4,534 mph)

*Comparing the three aircraft of the X-15 program.*
*Photo: B. Huber | Wikimedia Commons*

The three X-15s that were built were, albeit unofficially, called Ship 1, Ship 2, and Ship 3 – the fastest of which was the Ship #2.

*An engine failure in the Ship#2 meant that the pilot Jack McKay had to make an emergency landing at Mud Lake, NV.*
*Photo: NASA*

Pilot Jack McKay was promptly rescued by an Air Force medical team. After the crash, he recovered to fly the X-15 again, as he took to the skies on the X-15 twenty-two more times. Due to his injuries, he was eventually forced to retire from NASA.

Pilot Jack McKay in front of the X-15
Photo: NASA | Wikimedia Commons

On November 9, 1962, Pilot Jack MkKay:

“following the launch from the B-52 to begin flight 2-31-52, he started the X-15’s rocket engine, only to discover that it produced just 30 percent of its maximum thrust.”

– NASA

*During the crash, the X-15-2turned sideways and flipped onto its back.*
*Photo: NASA*

Following the crash, the X-15-2 was modified with higher propellant capacity and was tested with a new thermal protection material. It was rechristened to X-15A-2, and reached a speed of Mach 6.72 (4,534 mph) – the fastest for any X-15.

*The second North American X-15 rocket plane (serial 56-6671) transformed to X-15A-2 standard with its two external fuel tanks*
*Photo: NASA | Wikimedia Commons*

The extra fuel, which could be accommodated in the external fuel tanks, allowed “more full thrust time, totaling 141 seconds—50 seconds more than the basic X-15 Nos. 1 and 2.”

*X-15-A2 in ablative coating to protect it from high temperatures of supersonic flight.*
*Photo: NASA | Wikimedia Commons*

This pink eraser-like substance that the ship #2 was then covered with a white sealant coat which was one of the contributing factors to the flight achieving a record speed of 4,520 mph (Mach 6.7).

X-15-3

Air Force Serial	56-6672
Number of Flights	65
Highest Speed Recorded	6.72 (4,534 mph)

*Ship #3 at Edwards Air Force Base, Edwards, California*
*Photo: NASA | Wikimedia Commons*

Ship #3 used in the X-15 program had a wingspan of 22 ft, an empty weight of 14,000 lbs, and a maximum altitude of 354,200 feet. The aircraft was the only one in the X-15 program to have met a fatal accident.

Crash site of the X-15-3
Photo: NASA | Wikimedia Commons

Ship #3 began a slow drift in heading, which soon became a spin. Adams radioed that the X-15 “seems squirrelly,” and then said “I’m in a spin.” Through some combination of pilot technique and basic aerodynamic stability, Adams recovered from the spin, and entered an inverted Mach 4.7 dive.

– NASA

*The wreckage of North American X-15-3, which crashed on November 15, 1967, killing USAF astronaut Michael J. Adams.*
*Photo: NASA | Wikimedia Commons*

As the X-15 plummeted into the increasingly thicker atmosphere, the Honeywell adaptive flight control system caused the vehicle to begin oscillating. As the pitching motion increased, aerodynamic forces finally broke the aircraft into several major pieces. Adams was killed when the forward fuselage impacted the desert. This was the only fatal accident during the entire X-15 program.

– NASA

*Ship #3 achieved a maximum altitude of 354,200 feet, a record.*
*Photo: NASA | Wikimedia Commons*

The aircraft used to launch the X-15

Two aircraft were used to launch the X-15. These aircraft were known as “mother ship” and helped save fuel as the X-15 would be only applying thrust at an altitude where the air density was low.

NB-52A

Before the hypersonic aircraft was ready to take to the skies on its own, it had to be mounted on a pylon under the B-52’s right wing. The X-15 was released at an altitude of 37,550 feet. This retired aircraft is on display at the Pima Air and Space Museum.

Air Force Serial	52-003
Nickname	The High and Mighty One
Retired	October 1969

NB-52B

Air Force Serial	52-008
Nickname	The Challenger
Retired	November 2004

*North American X-15A-2 carried by NASA Boeing NB-52B mothership 52-0008.*
*Photo: U.S. Air Force | Wikimedia Commons*

The NB–52B with Tail Number (TN) 008 was the launch aircraft on 140 of the 199 X-15 flights. TN-008 flew an aggregate of 159 captive-carry and launch missions in that program.