Tag Archives: North American Aviation X-15A

22 August 1963

Joe Walker and the X-15 on Rogers Dry Lake at the end of a flight. Walker is wearing a David Clark Co. MC-2 full-pressure suit. (U.S. Air Force)

22 August 1963: On his twenty-fifth and last flight with the X-15 program, NASA Chief Research Test Pilot Joseph Albert Walker would attempt a flight to Maximum Altitude. Engineers had predicted that the X-15 was capable of reaching 400,000 feet (121,920 meters) but simulations had shown that a safe reentry from that altitude was risky. For this flight, Flight 91, the flight plan called for 360,000 feet (109,728 meters) to give Walker a safety margin. Experience had shown that slight variations in engine thrust and climb angle could cause large overshoots in peak altitude, so this was not considered an excessive safety margin.

For this flight, Joe Walker flew the Number 3 X-15, 56-6672. It was the only one of the three North American Aviation X-15s equipped with the Honeywell MH-96 flight control system, which had been developed to improve control of the rocketplane outside Earth’s atmosphere. This flight was the twenty-second for Number 3.

North American Aviation X-15 56-6672 immediately after being dropped by the Boeing NB-52 Stratofortress. (NASA)
North American Aviation X-15A 56-6672 immediately after being dropped by the Boeing NB-52 Stratofortress. (NASA)

Walker and the X-15 were airdropped from the Boeing NB-52A Stratofortress 52-003, The High and Mighty One, at 45,000 feet (13,716 meters) above Smith Ranch Dry Lake, Nevada, about half-way between the city of Reno and the NASA High Range Tracking Station at Ely. Launch time was 10:05:57.0 a.m., PDT. Walker ignited the Reaction Motors XLR99-RM-1 rocket engine. This engine was rated at 57,000 pounds of thrust. Experience had shown that different engines varied from flight to flight and that atmospheric conditions were a factor. Thrust beyond 60,000 pounds was often seen, but this could not be predicted in advance. The flight plan called for the duration of burn to be 84.5 seconds on this flight. The X-15 climbed at a 45° angle.

As Walker was about to shut down the engine according to plan, it ran out of fuel. The total burn time was 85.8 seconds, just slightly longer than planned.

“At burnout, Joe was passing 176,000 feet [53,645 meters] and traveling at 5,600 feet per second [1,707 meters per second]. He then began the long coast to peak altitude. It would take almost 2 minutes to reach peak altitude after burn out. Two minutes does not seem like a lot of time, but try timing it. Just sit back in your easy chair and count off the seconds. It is almost impossible to believe that you can continue to coast up in altitude for that length of time after the engine burns out. It gives you some feel for how much energy is involved at those speeds. For comparison, when you throw a ball up in the air as hard as you can, it only coasts upward a maximum of 4 or 5 seconds. The X-15 coasted up for 120 seconds.

“The airplane would coast up another 178,000 feet [54,254 meters] during that time to peak out at 354,200 feet. . . .” [107,960 meters]

At The Edge of Space: The X-15 Flight Program, by Milton O. Thompson, Smithsonian Institution Press, Washington, 1992, Chapter 5 at Page 125.

Joe Walker and the X-15 reached the peak of their ballistic trajectory at 354,200 feet (67.083 miles, 107,960 meters). Walker pitched the nose down to be in the proper attitude for atmospheric reentry. The X-15 decelerated as it hit the atmosphere and Walker experienced as much as 7 Gs. The rocketplane’s aerodynamic control surfaces again became operational as it descended through 95,000 feet (28,956 meters) and Walker leveled at 70,000 feet (21,336 meters). He then glided to a landing on Rogers Dry Lake at Edwards Air Force Base, California, after 11 minutes, 8.6 seconds of flight.

Flight 91 was the highest flight achieved by any of the X-15s. It was Joe Walker’s second flight into space. His record would stand for the next 41 years.

© 2016, Bryan R. Swopes

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12 August 1960

Major Robert M. White, U.S. Air Force. (NASA)

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.

An X-15 is dropped from the NB-52A, 52-003, at an altitude of 45,000 feet at 0.8 Mach. (NASA)

© 2016, Bryan R. Swopes

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29 June 1965

Captain Joe Henry Engle, United States Air Force
Captain Joe Henry Engle, United States Air Force

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.

Command Pilot Astronaut insignia, United States Air Force
Command Pilot Astronaut insignia, United States Air Force

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.

Captain Joe H. Engle, U.S. Air Force, with the North American Aviation X-15A-2, 56-6671, at Edwards Air Force Base, California, 1965. (NASA)
Captain Joe H. Engle, U.S. Air Force, with the North American Aviation X-15A-2, 56-6671, at Edwards Air Force Base, California, 1965. (NASA)

© 2016, Bryan R. Swopes

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27 June 1963

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.

North American Aviation X-15 56-6672 immediately after being dropped by the Boeing NB-52 Stratofortress. (NASA)
North American Aviation X-15 56-6672 immediately after being dropped by the Boeing NB-52 Stratofortress. (NASA)

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.

Command Pilot Astronaut insignia, United States Air Force
Command Pilot Astronaut insignia, United States Air Force

© 2015, Bryan R. Swopes

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23 June 1961

Bob White exits the cockpit of an X-15 on Rogers Dry Lake. (NASA)

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.

North American Aviation X-15A 56-6671. (NASA)

© 2016, Bryan R. Swopes

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