12 August 1960: At Edwards Air Force Base, California, Major Robert M. White flew the North American Aviation X-15 rocketplane to an altitude of 136,500 feet (41,605 meters), exceeding the previous unofficial record of 126,200 feet (38,466 meters) set by the late Captain Iven C. Kincheloe, Jr., with the Bell X-2, 7 September 1956.
Iven Kincheloe had been assigned as the Air Force’s project pilot for the X-15. When he was killed on a routine flight, Bob White was designated to replace him.
This was White’s fourth flight in an X-15, and the 19th flight of the X-15 Program. The Number 1 rocketplane, serial number 56-6670, was carried aloft under the right wing of the “mothership,” Boeing NB-52A Stratofortress 52-003. At 08:48:43.0 a.m., PDT, 56-6670 was dropped over Silver Lake, near the Nevada-California border. White fired the two Reaction Motors XLR11-RM-13 rocket engines and they burned for 256.2 seconds.
This flight took place in Phase II of the Program and was intended to gradually increase the envelope of X-15 performance with the XLR11 engines while waiting for the much more powerful XLR99. The purpose of Flight 19 was to reach maximum altitude in order to test the rocketplane’s stability and controllability above the atmosphere.
The X-15 accelerated to Mach 2.52, 1,773 miles per hour (2,853 kilometers per hour) while climbing at nearly a 70° angle and reached a peak altitude of 136,500 feet (41,605 meters). After engine shutdown, White glided to a landing on Rogers Dry Lake and touched down. The duration of the flight was 11 minutes, 39.1 seconds.
Neither Kincheloe’s or White’s altitudes are recognized as records by the Fédération Aéronautique Internationale(FAI). Over the next few years, the X-15 would reach to nearly three times higher.
29 June 1965: At 10:21:17.6 PDT, Captain Joe H. Engle, United States Air Force, flying the Number Three North American Aviation X-15A-3 research rocketplane, 56-6672, was air-dropped from the NB-52B Stratofortress mothership, Balls 8, over Delamar Dry Lake in Nevada. This was the 138th flight of the X-15 Program, and Joe Engle’s 12th. He fired the Reaction Motors XLR99-RM-1 engine for 81.0 seconds and accelerated to Mach 4.94 (3,432 miles per hour, 5,523 kilometers per hour). The X-15 climbed to an altitude of 280,600 feet (85,527 meters, 53.14 miles). He touched down at Edwards Air Force Base after 10 minutes, 34.2 seconds of flight. His parents were at Edwards to witness his flight.
Captain Engle qualified for Astronaut wings on this flight, the third and youngest Air Force pilot to do so.
From 1963 and 1965, Joe Engle made 14 flights in the three X-15s. After leaving the X-15 Program, he was assigned to the Apollo Program, the only NASA astronaut with prior spaceflight experience. He was the back-up Lunar Module pilot for Apollo 14 and he was the designated LM pilot for Apollo 17 but was replaced by Harrison Schmidt when Apollo 18 was cancelled. Next he went on to the Space Shuttle Program. He was a Mission Commander for the Enterprise flight tests and for Columbia‘s second orbital flight, during which he became the only pilot to manually fly a Mach 25 approach and landing. Finally, he commanded the Discovery STS 51-1 mission.
Joe Engle retired from the Air Force in 1986. He was then promoted to the rank of Major General and assigned to the Kansas Air National Guard. He has flown at least 185 aircraft types and accumulated 14,700 flight hours, with 224 hours in space.
27 June 1963: At 09:56:03.0 PDT, Major Robert A. Rushworth, United States Air Force, flying the Number Three North American Aviation X-15 research rocketplane, 56-6672, was air-dropped from the NB-52B Stratofortress mothership, Balls 8, over Delamar Dry Lake in Nevada.
This was the 87th flight of the X-15 Program, and Bob Rushworth’s 14th.
Rushworth fired the Reaction Motors XLR99-RM-1 engine for 80.1 seconds and accelerated to Mach 4.89 (3,425 miles per hour, 5,512 kilometers per hour). The X-15 climbed to an altitude of 285,000 feet (86,868 meters, 53.98 miles). Rushworth touched down at Edwards Air Force Base after 10 minutes, 28.0 seconds of flight.
Major Rushworth qualified for Astronaut wings on this flight, the second X-15 pilot to do so.
From 1960 and 1966, Bob Rushworth made 34 flights in the three X-15s, more than any other pilot.
23 June 1961: Major Robert Michael White, United States Air Force, became the first pilot to exceed Mach 5 in an aircraft. This was the 38th flight of the X-15 Program. Flights during this phase incrementally increased the speed and altitude of the X-15 up to its design limits of Mach 6 and 250,000 feet (76,200 meters).
The second North American Aviation X-15A, 56-6671, was air-dropped from the NB-52A Stratofortress mothership, 52-003, over Mud Lake, Nevada at 2:00:05.0 p.m., Pacific Daylight Time (21:00 UTC). White fired the Reaction Motors XLR99-RM-1 engine for 78.7 seconds, reaching Mach 5.27 (3,603 miles per hour, 5,799 kilometers per hour) and climbed to 107,700 feet (32,827 meters). 10 minutes, 5.7 seconds after being dropped from the B-52, White touched down on Rogers Dry Lake at Edwards Air Force Base.
Bob White was the first pilot to exceed Mach 4, Mach 5 and Mach 6. He also flew an X-15 to an altitude of 314,750 feet (95,936 meters), qualifying for U.S. Air Force astronaut wings.
After leaving the X-15 program, Major White flew 70 combat missions in the Republic F-105D Thunderchief fighter bomber during the Vietnam War. He lead the attack against the heavily-defended Paul Doumer Bridge in Hanoi, 11 August 1967, for which he was awarded the Air Force Cross.
Major General White retired from the U.S. Air Force in 1981. He died 10 March 2010.
56-6671 is in the collection of the National Museum of the United States Air Force. The mothership, 52-003, is on display at the Pima Air and Space Museum, Tucson, Arizona.
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.