10 June 1969: The U.S. Air Force donated the first North American Aviation X-15, serial number 56-6670, to the Smithsonian Institution for display at the National Air and Space Museum.
The first of three X-15A hypersonic research rocketplanes built by North American for the Air Force and the National Advisory Committee (NACA, the predecessor of NASA), 56-6670 made the first glide flight and the first and last powered flights of the X-15 Program. It made a total of 82 of the 199 X-15 flights.
Scott Crossfield, North American’s Chief Engineering Test Pilot, made the first unpowered flight 8 June 1959 and the first powered flight, 17 September 1959. NASA Research Test Pilot William H. “Bill” Dana made the final X-15 flight on 24 October 1968.
8 June 1959: At Edwards Air Force Base, California, North American Aviation’s Chief Engineering Test Pilot, A. Scott Crossfield, made the first flight of the X-15A hypersonic research rocketplane.
56-6670 was the first of three X-15s built for the U.S. Air Force and NASA. It was airdropped from a Boeing NB-52A Stratofortress, 52-003, at 37,550 feet (11,445 meters) over Rosamond Dry Lake at 08:38:40 a.m, Pacific Daylight Time.
This was an unpowered glide flight to check the flying characteristics and aircraft systems, so there were no propellants or oxidizers aboard, other than hydrogen peroxide which powered the pumps and generators.
The aircraft reached 0.79 Mach (522 miles per hour, 840 kilometers per hour) during the 4 minute, 56.6 second flight.
In his autobiography, Scott Crossfield described the first flight:
“Three” . . . “Two” . . . “One” . . .
Inside the streamlined pylon, a hydraulic ram disengaged the three heavy shackles from the upper fuselage of the X-15. They were so arranged that all released simultaneously, and if one failed they all failed. The impact of the release was clearly audible in the X-15 cockpit. I heard a loud “kerchunk.”
The X-15 hung in its familiar place beneath the pylon for a split second. Then the nose dipped sharply down and to the right more rapidly than I had anticipated. The B-52, so long my constant companion, was gone. The X-15 and I were alone in the air and flying 500 miles an hour. In less than five minutes I would be on the ground. . . .
There was much to do in the first hundred seconds of flight. First I had to get the “feel” of the airplane, to make certain it was trimmed out for landing just as any pilot trims an airplane after take-off or . . . when dwindling fuel shifts the center of gravity. Then I had to pull the nose up, with and without flaps, to feel out the stall characteristics, so that I would know how she might behave at touchdown speeds . . . My altimeter unwound dizzily: from 24,000 to 13,000 feet in less than forty seconds. . . .
The desert was coming up fast. At 600 feet altitude I flared out. . . .
In the next second without warning the nose of the X-15 pitched up sharply. It was a maneuver that had not been predicted by the computers, an uncharted area which the X-15 was designed to explore. I was frankly caught off guard. Quickly I applied corrective elevator control.
The nose went down sharply. But instead of leveling out, it tucked down. I applied reverse control. The nose came up but much too far. Now the nose was rising and falling like a skiff in a heavy sea. Although I was putting in maximum control I could not subdue the motions. The X-15 was porpoising wildly, sinking toward the desert at 200 miles an hour. I would have to land at the bottom of an oscillation, timed perfectly; otherwise, I knew, I would break the bird. I lowered the flaps and the gear. . . .
. . . With the next dip I had one last chance and flared again to ease the descent. At that moment the rear skids caught on the desert floor and the nose slammed over, cushioned by the nose wheel. The X-15 skidded 5,000 feet across the lake, throwing up an enormous rooster tail of dust. . . .
—Always Another Dawn: The Story of a Rocket Test Pilot, by A. Scott Crossfield and Clay Blair, Jr., The World Publishing Company, Cleveland and New York, 1960, Chapter 37 at Pages 338–342.
Before the drop, it was discovered that the aircraft’s Stability Augmentation System was inoperative in pitch mode. During the flight it was found that the hydraulic-assisted flight control system was responding too slowly to Crossfield’s inputs. Engineers analyzed the problem and increased the hydraulic system pressure. The problem never recurred.
Scott Crossfield was the world’s most experienced rocketplane pilot with 82 rocketplane flights before the X-15 program. “. . . he was intimately involved in the design of the aircraft and contributed immensely to the success of the design.”
—At The Edge Of Space, by Milton O. Thompson, Smithsonian Institution Press, 1992, Introduction, at Page 3.
North American Aviation X-15A 56-6670 made the first glide flight and the first and last powered flights of the X-15 Program. It made a total of 82 of the 199 X-15 flights. 56-6670 is in the collection of National Air and Space Museum at Washington, D.C.
30 April 1962: The Chief Research Test Pilot at NASA’s High Speed Flight Station, Joseph Albert Walker, flew the first North American Aviation X-15 hypersonic research aircraft, 56-6670, on its twenty-seventh flight. This was Flight 52 of the NASA X-15 Hypersonic Research Program. The purpose of this test flight was to explore aerodynamic heating and stability at very high altitudes.
At an altitude of approximately 45,000 feet (13,716 meters) over Mud Lake, Nevada, the X-15 was released from Balls 8, the NB-52B drop ship, at 10:23:20.0 a.m., Pacific Daylight Savings Time.
Walker started the Reaction Motors XLR99-RM-1 rocket engine. The planned burn time was 81.0 seconds, but the engine ran slightly longer: 81.6 seconds. Even with the longer burn, the X-15 undershot the planned speed of Mach 5.35 and peak altitude of 255,000 feet (77,724 meters). The actual maximum speed for this flight was Mach 4.94, and maximum altitude, 246,700 feet (75,194 meters). Walker landed on Rogers Dry Lake. The total duration of Flight 52 was 9 minutes, 46.2 seconds.
Even though the peak altitude reached by the X-15 was 8,300 feet (2,530 meters) lower than expected, Joe Walker established a new Fédération Aéronautique Internationale (FAI) World Record for Altitude Gain, Aeroplane Launched from a Carrier Aircraft, of 61,493 meters (201,749 feet).¹
13 April 1960: Major Robert M. White, USAF, made the first flight of an X-15 by an Air Force test pilot.
Carried aloft by a Boeing NB-52A Stratofortress, serial number 52-003, the first of three X-15 hypersonic research aircraft, 56-6670, was airdropped at 0915 above Rosamond Dry Lake. Major White ignited the two Reaction Motors XLR-11 rocket engines and with a burn time of 4 minutes, 13.7 seconds, the X-15 accelerated to Mach 1.9 (1,254 miles per hour/2,018 kilometers per hour) and reached 48,000 feet (14,630 meters). Both numbers were slightly short of the planned Mach 2.0 (1,320 miles per hour/2,124 kilometers per hour) and 50,000 feet (15,240 meters).
After 8 minutes, 52.7 seconds, Bob White and the X-15 touched down at Edwards Air Force Base.
Over the next 32 months Bob White made 16 flights in the X-15. He was the first pilot to fly faster than Mach 4, Mach 5 and Mach 6. He flew it to Mach 6.04, 4,093 miles per hour (6,587 kilometers per hour) and set a Fédération Aéronautique Internationale (FAI) altitude record of 314,750 feet (95,936 meters), for an altitude gain of 82,190 meters (269,652 feet).¹
White was one of three pilots awarded astronaut wings for his flights in the X-15.
24 March 1960: After North American Aviation’s Chief Engineering Test Pilot, Albert Scott Crossfield, had made the first flights in the new X-15 hypersonic research rocketplane (one gliding, eight powered), NASA Chief Test Pilot Joseph Albert Walker made his first familiarization flight.
The X-15, 56-6670, the first of three built by North American Aviation, Inc., was carried aloft under the right wing of a Boeing NB-52A Stratofortress, 52-003, flown by John E. Allavie and Fitzhugh L. Fulton.
The rocketplane was dropped from the mothership over Rosamond Dry Lake at 15:43:23.0 local time, and Joe Walker ignited the Reaction Motors XLR-11 rocket engine. The engine burned for 272.0 seconds, accelerating Walker and the X-15 to Mach 2.0 (1,320 miles per hour/2,124.3 kilometers per hour) and a peak altitude of 48,630 feet (14,822.4 meters). Walker landed on Rogers Dry Lake at Edwards Air Force Base after a flight of 9 minutes, 8.0 seconds.
Joe Walker made 25 flights in the three X-15 rocket planes from 24 March 1960 to 22 August 1963. He achieved a maximum Mach number of 5.92, maximum speed of 4,104 miles per hour (6,605 kilometers per hour) and maximum altitude of 354,200 feet (107,960 meters).
Joe Walker was killed in a mid-air collision between his Lockheed F-104N Starfighter and a North American Aviation XB-70A Valkyrie near Barstow, California, 1 June 1966.
The number one ship, 56-6670, made 81 of the 199 flights of the X-15 Program. It was the first to fly, and also the last, 24 October 1968. Today, it is in the collection of the Smithsonian Institution National Air and Space Museum.