Tag Archives: NASA X-15 Hypersonic Research Program

North American Aviation, Inc., X-15A Hypersonic Research Rocketplane

December 20, 2024Aviation56-6670, 56-6671, 56-6672, Boeing NB-52A Stratofortress, Boeing NB-52B Stratofortress, Edwards Air Force Base, Full-Pressure Suit, Inconel X, NASA X-15 Hypersonic Research Program, North American Aviation Inc., North American Aviation Model NA-240, North American Aviation X-15A, Reaction Motors XLR11-RM-13, Reaction Motors XLR99-RM-1, Rogers Dry LakeBryan Swopes

Rollout AFFTC History Office — North American Aviation, Inc., X-15A-1, 56-6670, at Los Angeles Division, October 1958. (Air Force Flight Test Center History Office)

20 December 1968: After 199 flights, the National Aeronautics and Space Administration cancelled the X-15 Hypersonic Research Program. A 200th X-15 flight had been scheduled, but after several delays, the decision was made to end the program. (The last actual flight attempt was 12 December 1968, but snow at several of the dry lakes used as emergency landing areas resulted in the flight being cancelled.)

The X-15A rocketplane was designed and built for the U.S. Air Force and the National Advisory Committee for Aeronautics (NACA, the predecessor of NASA) by North American Aviation, Inc., to investigate the effects of hypersonic flight (Mach 5+). Design work started in 1955 and a mock-up had been completed after just 12 months. The three X-15s were built at North American’s Los Angeles Division, at the southeast corner of Los Angeles International Airport (LAX), on the shoreline of southern California.

The first flight took place 8 June 1959 with former NACA test pilot Albert Scott Crossfield in the cockpit of the Number 1 ship, 56-6670.

Scott Crossfield prepares for a flight in the North American Aviation X-15A.

While earlier rocketplanes, the Bell X-1 series, the the Douglas D-558-II, and the Bell X-2, were airplanes powered by rocket engines, the X-15 was a quantum leap in technology. It was a spacecraft.

Like the other rocketplanes, the X-15 was designed to be carried aloft by a “mothership,” rather than to takeoff and climb to the test altitude under its own power. The carrier aircraft was originally to be a Convair B-36 intercontinental bomber but this was soon changed to a Boeing B-52 Stratofortress. Two B-52s were modified to carry the X-15: NB-52A 52-003, The High and Mighty One, and NB-52B 52-008, Balls 8.

From 8 June 1959 to 24 October 1968, the three X-15s were flown by twelve test pilots, three of whom would qualify as astronauts in the X-15. Two would go on to the Apollo Program, and one, Neil Alden Armstrong, would be the first human to set foot on the surface of the Moon, 20 July 1969. Joe Engle would fly the space shuttle. Four of the test pilots, Petersen, White, Rushworth, and Knight, flew in combat during the Vietnam War, with Bob White being awarded the Air Force Cross. Petersen, Rushworth and White reached flag rank.

One pilot, John B. (“Jack”) McKay, was seriously injured during an emergency landing at Mud Lake, Nevada, 9 November 1962. Another, Michael James Adams, was killed when the Number 3 ship, 56-6672, went into a hypersonic spin and broke up on the program’s 191st flight, 15 November 1967.

North American Aviation, Inc. X-15A 56-6670 on Rogers Dry Lake, Edwards Air Force Base, California. (NASA) — North American Aviation, Inc., X-15A-1 56-6670 on Rogers Dry Lake, Edwards Air Force Base, California. (NASA Image E-5251)

Flown by a single pilot/astronaut, the X-15 is a mid-wing monoplane with dorsal and ventral fin/rudders and stabilators. The wing had no dihdral, while the stabilators had a pronounced -15° anhedral. The short wings have an area of 200 square feet (18.58 square meters) and a maximum thickness of just 5%. The leading edges are swept to 25.64°. There are two small flaps but no ailerons. The entire vertical fin/rudder pivots for yaw control.

Above 100,000 feet (30,840 meters) altitude, conventional aircraft flight control surfaces are ineffective. The X-15 is equipped with a system of reaction control jets for pitch, roll and yaw control. Hydrogen peroxide was passed through a catalyst to produce steam, which supplied the control thrusters.

The forward landing gear consists of a retractable oleo strut with steerable dual wheels and there are two strut/skids at the rear of the fuselage. The gear is retracted after the X-15 is mounted on the NB-52 and is extended for landing by its own weight.

North American Aviation X-15A 56-6672 touches down on Rogers Dry Lake. (NASA) — North American Aviation, Inc., X-15A-3 56-6672 just before touch down on Rogers Dry Lake. (NASA Image E-7469)

The rocketplane’s cockpit featured both a conventional control stick as well as side-controllers. It was pressurized with nitrogen gas to prevent fires. The pilot wore an MC-2 full-pressure suit manufactured by the David Clark Company of Worcester, Massachusetts, with an MA-3 helmet. The suit was pressurized below the neck seal with nitrogen, while the helmet was supplied with 100% oxygen. This pressure suit was later changed to the Air Force-standardized A/P22S.

X-15A cockpit with original Lear Siegler instrument panel. (NASA) — X-15 cockpit with original Lear Siegler instrument panel. (NASA image E63-9834)

The X-15 is 50.75 feet (15.469 meters) long with a wing span of 22.36 feet (6.815 meters). The height—the distance between the tips of the dorsal and ventral fins—is 13.5 feet (4.115 meters). The stabilator span is 18.08 feet (5.511 meters). The fuselage is 4.67 feet (1.423 meters) deep and has a maximum width of 7.33 feet (2.234 meters).

Since the X-15 was built of steel rather than light-weight aluminum, as are most aircraft, it is a heavy machine, weighing approximately 14,600 pounds (6,623 kilograms) empty and 34,000 pounds (15,422 kilograms) when loaded with a pilot and propellants. The X-15s carried as much as 1,300 pounds (590 kilograms) of research instrumentation, and the equipment varied from flight to flight. The minimum flight weight (for high-speed missions): 31,292 pounds (14,194 kilograms) The maximum weight was 52,117 pounds (23,640 kilograms) at drop (modified X-15A-2 with external propellant tanks).

Initial flights were flown with a 5 foot, 11 inch (1.803 meters)-long air data boom at the nose, but this would later be replaced by the “ball nose” air sensor system. The data boom contained a standard pitot-static system along with angle-of-attack and sideslip vanes. The boom and ball nose were interchangeable.

Neil Armstrong with the first North American Aviation X-15A, 56-6670, on Rogers Dry Lake after a flight, 1960. His hand is resting on the rocketplane's ball nose sensor. (NASA) — NASA Research Test Pilot Neil A. Armstrong with the first North American Aviation X-15A, 56-6670, on Rogers Dry Lake after a flight, 1960. His right hand is resting on the rocketplane’s ball nose sensor. (NASA Image E60-6286)

The X-15s were built primarily of a nickel/chromium/iron alloy named Inconel X, along with corrosion-resistant steel, titanium and aluminum. Inconel X is both very hard and also able to maintain its strength at the very high temperatures the X-15s were subjected to by aerodynamic heating. It was extremely difficult to machine and special fabrication techniques had to be developed.

Delays in the production of the planned Reaction Motors XLR99 rocket engine forced engineers to adapt two vertically-stacked Reaction Motors XLR11-RM-13 four-chamber rocket engines to the X-15 for early flights. This was a well-known engine which was used on the previous rocketplanes. The XLR11 burned a mixture of ethyl alcohol and water with liquid oxygen. Each of the engines’ chambers could be ignited individually. Each engine was rated at 11,800 pounds of thrust (58.49 kilonewtons) at Sea Level.

Two Reaction Motors Division XLR11-RM-5 four-chamber rocket engines installed on an X-15. (NASA) — Two Reaction Motors Division XLR11-RM-13 four-chamber rocket engines installed on an X-15. The speed brakes of the ventral fin are shown in the open position. (NASA)

The Reaction Motors XLR99-RM-1 rocket engine was throttleable by the pilot from 28,500 to 60,000 pounds of thrust (126.77–266.89 kilonewtons). The engine was rated at 50,000 pounds of thrust (222.41 kilonewtons) at Sea Level; 57,000 pounds (253.55 kilonewtons) at 45,000 feet (13,716 meters), the typical drop altitude; and 57,850 pounds (257.33 kilonewtons) of thrust at 100,000 feet (30,480 meters). Individual engines varied slightly. A few produced as much as 61,000 pounds of thrust (271.34 kilonewtons).

The XLR99 burned anhydrous ammonia and liquid oxygen. The flame temperature was approximately 5,000 °F. (2,760 °C.) The engine was cooled with circulating liquid oxygen. To protect the exhaust nozzle, it was flame-sprayed with ceramic coating of zirconium dioxide. The engine is 6 feet, 10 inches (2.083 meters) long and 3 feet, 3.3 inches (0.998 meters) in diameter. It weighs 910 pounds (413 kilograms). The Time Between Overhauls (TBO) is 1 hour of operation, or 100 starts.

Thiokol Reaction Motors Division XLR-RM-1 rocket engine. (U.S. Air Force) — Thiokol Corporation Reaction Motors Division XLR99-RM-1 rocket engine. (U.S. Air Force)

The XLR99 proved to be very reliable. 169 X-15 flights were made using the XLR99. 165 of these had successful engine operation. It started on the first attempt 159 times.

The highest speed achieved during the program was with the modified number two ship, X-15A-2 56-6671, flown by Pete Knight to Mach 6.70 (6,620 feet per second/4,520 miles per hour/7,264 kilometers per hour) at 102,700 feet (31,303 meters). On this flight, the rocketplane exceeded its maximum design speed of 6,600 feet per second (2,012 meters per second).

The maximum altitude was reached by Joe Walker, 22 August 1963, when he flew 56-6672 to 354,200 feet (107,960 meters).

The longest flight was flown by Neil Armstrong, 20 April 1962, with a duration of 12 minutes, 28.7 seconds.

North American Aviation X-15A-1 56-6670 is on display at the Smithsonian Institution National Air and Space Museum. X-15A-2 56-6671 is at the National Museum of the United States Air Force.

A North American Aviation F-100 Super Sabre chase plane follows NB-52A 52-003 prior to launch of an X-15. (NASA)

5 December 1963

December 5, 2024Aviation, Space Flight52-008, 56-6670, Balls 8, Boeing NB-52B Stratofortress, Delamar Dry Lake, Edwards Air Force Base, Flight Test, NASA 670, NASA X-15 Hypersonic Research Program, North American Aviation Inc., North American Aviation X-15A, Reaction Motors XLR99-RM-1, Robert A. Rushworth, Test Pilot, X-15Bryan Swopes

5 December 1963: On Flight 97 of the X-15 Program, Major Robert A. Rushworth flew the number one aircraft, Air Force serial number 56-6670, to an altitude of 101,000 feet 30,785 meters) and reached Mach 6.06 (4,018 miles per hour/6,466 kilometers per hour).

The rocketplane was dropped from the Boeing NB-52B Stratofortress “mother ship” 52-008, Balls 8, flying at 450 knots (833.4 kilometers per hour) at 45,000 feet (13,716 meters) over Delamar Dry Lake, Nevada. Rushworth ignited the Reaction Motors XLR-99-RM-1 rocket engine, which burned for 81.2 seconds before shutting down.

The flight plan had called for an altitude of 104,000 feet (31,699 meters), a 78 second burn and a maximum speed of Mach 5.70. With the difficulties of flying such a powerful rocketplane, Rushworth’s flight was actually fairly close to plan. During the flight the right inner windshield cracked.

Bob Rushworth landed the X-15 on Rogers Dry Lake at Edwards Air Force Base, California, after a flight of 9 minutes, 34.0 seconds.

Mach 6.06 was the highest Mach number reached for an unmodified X-15.

56-6670 flew 81 of the 199 flights of the X-15 Program. It is in the collection of the Smithsonian Institution National Air and Space Museum.

From 1960 to 1966, Bob Rushworth made 34 flights in the three X-15s, more than any other pilot.

North American Aviation Inc./U.S. Air Force/NASA X-15A 56-6670 hypersonic research rocketplane on display at the National Air and Space Museum. (Photo by Eric Long, National Air and Space Museum, Smithsonian Institution)

29 November 1957

November 29, 2024Aviation52-003, Air Force Plant 42, Boeing NB-52A Stratofortress, Edwards Air Force Base, Mothership, NASA X-15 Hypersonic Research ProgramBryan Swopes

Boeing NB-52A 52-003 with a North American Aviation X-15 56 under its right wing at Edwards Air Force Base. (NASA DFRC EC62 0099) — Boeing NB-52A 52-003 with a North American Aviation X-15 under its right wing, at Edwards Air Force Base, 31 December 1961. (NASA)

29 November 1957: The third production Boeing B-52A-1-BO Stratofortress strategic bomber, 52-003, was flown from Boeing’s Seattle plant to the North American Aviation facility at Air Force Plant 42, Palmdale, California, to be modified to carry the new X-15 hypersonic research rocketplane.

Modifications began on 4 February 1958. A pylon was mounted under the bomber’s right wing. A large notch was cut into the trailing edge of the inboard flap for the X-15’s vertical fin. A 1,500 gallon (5,678 liter) liquid oxygen tank was installed in the bomb bay.

The X-15 was attached to this underwing pylon by three standard Air Force bomb shackles. (NASA) — The X-15 was attached to this underwing pylon by three remotely-actuated standard Air Force bomb shackles. (NASA)

To allow clearance for teh X-15's vertical fin, a notch had to be cut in the trailing edge of the inboard right flap. (NASA) — To allow clearance for the X-15’s vertical fin, a notch had to be cut in the trailing edge of the inboard right flap. (NASA)

A station for a launch operator was installed on the upper deck of the B-52 at the former electronic countermeasures position. A series of control panels allowed the panel operator to monitor the X-15’s systems, provide electrical power, and to keep the rocketplane’s liquid oxygen tank full as the LOX boiled off during the climb to launch altitude. The operator could see the X-15 through a plexiglas dome, and there were two television monitors.

After modifications were completed at Palmdale, 52-003 was flown to Edwards Air Force Base, 14 November 1958.

NB-52A 52-003 is on display at the Pima Air and Space Museum, Tucson, Arizona.

15 November 1967

November 15, 2024Aviation, Space Flight52-008, 56-6672, Aircraft Accident, Balls 8, Boeing NB-52B Stratofortress, Edwards Air Force Base, Flight 3-65 Accident, Flight 3-65-97, Flight Test, Michael James Adams, Mike Adams, NASA, NASA X-15 Hypersonic Research Program, National Aeronautics and Space Administration, North American Aviation Inc., North American Aviation X-15, North American Aviation X-15A-3, Randsburg, Rocketplane, Test PilotBryan Swopes

Major Michael J. Adams, United States Air Force, with an X-15 hypersonic research rocketplane on Rogers Dry Lake. (NASA) — Major Michael J. Adams, United States Air Force, with a North American Aviation X-15 hypersonic research rocketplane, 56-6670, on Rogers Dry Lake, after his third flight in the program, 22 March 1967. (NASA)

15 November 1967: Major Michael James Adams, United States Air Force, was killed in the crash of the number three North American Aviation X-15 hypersonic research rocketplane, 56-6672.

Flight 191 of the X-15 program was Mike Adams’ seventh flight in the rocketplane. It was the 56-6672’s 65th flight. The flight plan called for 79 seconds of engine burn, accelerating the X-15 to Mach 5.10 while climbing to 250,000 feet (76,200 meters). Adams’ wife, Freida, and his mother, Georgia Adams, were visiting in the NASA control room at Edwards Air Force Base.

Balls 8, the Boeing NB-52B Stratofortress, 52-008, flown by Colonel Joe Cotton, took off from Edwards at 9:12 a.m., carrying -672 on a pylon under its right wing, and headed north toward the drop point over Delamar Dry Lake in Nevada. The drop ship climbed to the launch altitude of 45,000 feet (13,716 meters).

The X-15 launch was delayed while waiting for the Lockheed C-130 Hercules rescue aircraft to arrive on station. This required Adams to reset the Honeywell MH-96 Automatic Flight Control System to compensate for the changing position of the sun in the sky.

North American Aviation X-15A-3 56-6672 immediately after launch over Delamar Lake, Nevada. Date unknown. (U.S. Air Force)

56-6672 was launched by Balls 8 at 10:30:07.4 a.m., Pacific Standard Time. As it dropped clear of the bomber, the rocketplane rolled 20° to the right, a normal reaction. Within one second, Mike Adams had started the XLR99-RM-1 rocket engine while bringing the wings level. The engine ignited within one-half second and was up to its full 57,000 pounds of thrust (253.549 kilonewtons) one second later. The engine ran for 82.3 seconds, 3.3 seconds longer than planned, causing the X-15 to reach Mach 5.20 (3,617 miles per hour/5,821 kilometers per hour) and to overshoot the planned altitude to peak at 266,000 feet (81,077 meters).

A North American Aviation X-15 hypersonic research rocketplane leaves a contrail as it climbs toward the edge of space. (NASA)

With the X-15 climbing through 140,000 feet (42,672 meters), the Inertial Flight Data System computer malfunctioned. Adams radioed ground controllers that the system’s malfunction lights had come on.

The flight plan called for a wing-rocking maneuver at peak altitude so that a camera on board could scan from horizon to horizon. During this maneuver, the Reaction Control System thrusters did not respond properly to Adams’ control inputs. The X-15 began to yaw to the right.

As it reached its peak altitude, 56-6672 yawed 15° to the left. Going over the top, the nose yawed right, then went to the left again. By the time the aircraft had descended to 230,000 feet (70,104 meters), it had pitched 40° nose up and yawed 90° to the right its flight path. The X-15 was also rolling at 20° per second. The rocketplane went into a spin at Mach 5.

10:33:37 Chase 1: “Dampers still on, Mike?”

10:33:39 Adams: “Yeah, and it seems squirrelly.”

10:34:02 Adams: “I’m in a spin, Pete.” [Major William J. “Pete” Knight, another X-15 pilot, was the flight controller, NASA 1]

10:34:05 NASA 1: “Let’s get your experiment in and the cameras on.”

10:34:13 NASA 1: “Let’s watch your theta, Mike.”

10:34:16 Adams: “I’m in a spin.”

10:34:18 NASA 1: “Say again.”

10:34:19 Adams: “I’m in a spin.”

Adams fought to recover, and at 118,000 feet (35,967 meters) came out of the spin, but he was in an inverted 45° dive at Mach 4.7. The X-15’s MH-96 Automatic Flight Control System entered a series of diverging oscillations in the pitch and roll axes, with accelerations up to 15 gs. Dynamic pressures on the airframe rapidly increased from 200 pounds per square foot (9.576 kilopascals) to 1,300 pounds per square foot (62.244 kilopascals).

At 62,000 feet (18,898 meters), still at Mach 3.93, the aircraft structure failed and it broke apart.

10:34:59 X-15 telemetry failed. Last data indicated it was oscillating +/- 13 g. Radar altitude was 62,000 feet (18,898 meters). The aircraft was descending at 2,500 feet per second (762 meters per second) and broke into many pieces at this time.

10:35:42 NASA 1: “Chase 4, do you have anything on him?”

10:35:44 Chase 4: “Chase 4, negative.”

10:35:47 NASA 1: “OK, Mike, do you read?”

10:35:52 Chase 4: “Pete, I got dust on the lake down there.”

North American Aviation X-15A-3 56-6672 crashed in a remote area, approximately 5½ miles (9 kilometers) north-northeast of Randsburg, California, a small village along U.S. Highway 395.

Major Michael James Adams was killed. This was the only pilot fatality of the entire 199-flight X-15 program.

North American Aviation X-15A 56-6672 on Rogers Dry Lake after a flight. (NASA) — North American Aviation X-15A-3 56-6672 on Rogers Dry Lake. (NASA)

An investigation by NASA’s Engineering and Safety Center determined that,

“. . . the root cause of the accident was an electrical disturbance originating from an experiment package using a commercial-off-the-shelf (COTS) component that had not been properly qualified for the X-15 environment. . .” and that there is “. . . no conclusive evidence to support the hypothesis that SD [spatial disorientation] was a causal factor. On the contrary, the evidence suggests that poor design of the pilot-aircraft interface and ineffective operational procedures prevented the pilot and ground control from recognizing and isolating the numerous failures before the aircraft’s departure from controlled flight was inevitable.”

—A Comprehensive Analysis of the X-15 Flight 3-65 Accident, NASA/TM—2014-218538 (Corrected Copy)

Crushed forward fuseleage of X-15 56-6672. (NASA) — Crushed forward fuselage of North American Aviation X-15A-3 56-6672. (NASA)

Michael James Adams was born at Sacramento, California, 5 May 1930. He was the first of two sons of Michael Louis Adams, a telephone company technician, and Georgia E. Domingos Adams.

Michael Adams throws a javelin at Sacramento J.C. (1949 Pioneer)

After high school, Mike Adams attended Sacramento Junior College, graduating in 1949. He was an outfielder for the college baseball team, and threw the javelin in track & field.

Adams enlisted in the United States Air Force in 1950. He completed basic training at Lackland Air Force Base, San Antonio, Texas. In October 1951, he was selected as an aviation cadet and sent to Spence Air Force Base, near Moultrie, Georgia, for primary flight training. Cadet Adams completed flight training at Webb Air Force Base, Big Spring, Texas. He graduated 25 October 1952. Adams was one of two distinguished graduates in his class and received a commission as an officer in the regular Air Force.

Second Lieutenant Adams was assigned to advanced flight training at Nellis Air Force Base, where he flew the Lockheed F-80 Shooting Star and North American Aviation F-86 Sabre.

In April 1953, Lieutenant Adams joined the 80th Fighter-Bomber Squadron at K-13, Suwon, Republic of Korea. He flew 49 combat missions.

Mr. and Mrs. Michael J. Adams, 15 January 1955. (Freida Adams Collection)

Following the Korean War, Lieutenant Adams was assigned to the 613th Fighter Bomber Squadron, 401st Fighter-Bomber Group, at England Air Force Base, Alexandria, Louisiana. The Squadron initially flew the F-86F Sabre and then transitioned to the Republic F-84F Thunderstreak. Adams deployed to Chaumont Air Base, France, for a six-month temporary assignment.

While stationed at England AFB, Lieutenant Adams met Miss Freida Beard. They were married in a ceremony at the Homewood Baptist Church in Alexandria, 15 January 1955. They would have three children, Michael James, Jr., Brent, and Liese Faye Adams.

In 1958, Adams graduated from the University of Oklahoma at Norman, with a bachelor’s degree in aeronautical engineering. He was a member of the university’s Institute of Aeronautical Sciences. Adams was next assigned to the Massachusetts Institute of Technology, Cambridge, Massachusetts, where he studied astronautics.

Adams’ next military assignment was as a maintenance officer course instructor at Chanute Air Force Base, Rantoul, Illinois.

In 1962, Captain Adams entered an eight-month training program at the Air Force Test Pilot School, Class 62C, at Edwards Air Force Base in the high desert of southern California. He was awarded the A.B. Honts Trophy as the class’s outstanding graduate.

Captain Michael J. Adams with a Northrop F-5A. (NASA)

On 17 June 1963, Captain Adams entered the Aerospace Research Pilots School, which was also at Edwards. This was a seven-month course that taught flying skills in advanced vehicles, with an aim to prepare the graduates for space flight, and to create a pool of qualified military test pilots to be selected as astronauts. The Air Force estimated a need for 20 pilots a year for the upcoming X-20 Dyna-Soar and Manned Orbiting Laboratory (M.O.L.) programs. Adams graduated with the second of the four ARPS classes.

Adams then became an operational test pilot, conducting stability and control tests for the Northrop F-5A Freedom Fighter. That was followed by an assignment as a project pilot for the Cornell Aeronautical Laboratory.

On 13 November 1963, it was announced that Michael Adams was on of the selectees for the M.O.L. program. As a designated Air Force astronaut, Adams was involved in lunar landing simulations during the development of the Apollo Program lunar lander.

Artists conception of the U.S. Air Force Manned Orbiting Laboratory (M.O.L.)

Major Adams was selected as a pilot of the NASA/Air Force X-15 Hypersonic Research Flight Program. (He was the twelfth and final pilot to be accepted into the project.) He made his first X-15 flight on 6 October 1966. He flew the first X-15, 56-6770. A ruptured fuel tank forced him to make an emergency landing at Cuddeback Dry Lake, one of several pre-selected emergency landing sites, about 40 miles (64 kilometers) northeast of Edwards. The duration of the flight was 8 minutes, 26.4 seconds. The X-15 had only reached an altitude of 75,400 feet (22,982 meters) and Mach 3.00.

A North American Aviation X-15 at Cuddeback Lake after an emergency landing. A Piasceki HH-21C is standing by. (U.S. Air Force)

His second flight took place on 29 November 1966. On this flight, he took the # 3 ship, 56-6672, to 92,100 feet (28,072 meters) and Mach 4.65. The flight lasted 7 minutes, 55.9 seconds.

For his third flight, Mike Adams was back in 56-6670, which had been repaired. He flew to an altitude of 133,100 feet (40,569 meters) and reached Mach 5.59 (3,822 miles per hour/6,151 kilometers per hour). This was Adams fastest flight. He landed at Edwards after 9 minutes, 27.9 seconds.

Flight number four for Adams took place on 28 April 1967. Again he flew the # 1 X-15. On this flight, he reached 167,200 feet (50,963 meters) and Mach 5.44. Elapsed time was 9 minutes, 16.0 seconds.

On 15 June 1967, Adams flew # 1 to 229,300 feet (69,891 meters) and Mach 5.14. Duration 9 minutes, 11.0 seconds.

On 25 August 1967, Adams made his sixth flight, his second in the third X-15, 56-6672. The rocket engine shut down after sixteen seconds and had to be restarted. The maximum altitude was 84,400 feet (25,725 meters) and Mach 4.63. The duration of this flight was 7 minutes. 37.0 seconds.

Mike Adams’ seventh flight in an X-15 took place 15 November 1967. This was the 191st X-15 flight, and the 65th for X-15 56-6672. Tests to be conducted were an ultraviolet study of the rocketplane’s exhaust plume; solar spectrum measurements; micrometeorite collection, and a test of ablative material for the Saturn rocket.

Adams reached 266,000 feet (81,077 meters) and Mach 5.20.

Having met the U.S. Air Force qualification for flight in excess of 50 miles (80.47 kilometers), Michael Adams was posthumously awarded the wings of an astronaut.

Major Michael James Adams, United States Air Force, was buried at Mulhearn Memorial Park, in Monroe, Louisiana.

9 November 1962

November 9, 2024Aviation, Space Flight52-008, 56-6671, Aircraft Accident, Balls 8, Boeing NB-52B Stratofortress, Emergency Landing, Flight Test, Inflight Emergency, Jack McKay, John Barron McKay, Mud Lake, NASA, NASA X-15 Hypersonic Research Program, North American Aviation Inc., North American Aviation X-15A, North American Aviation X-15A-2, Reaction Motors XLR99-RM-1, Test PilotBryan Swopes

9 November 1962: Flight 74 of the X-15 Program was the Number Two aircraft’s 31st flight. X-15 56-6671 was carried aloft by Balls 8, the Boeing NB-52B Stratofortress, 53-008, for launch over Mud Lake, Nevada. NASA test pilot John Barron (“Jack”) McKay was to take the rocketplane to 125,000 feet at Mach 5.5 to investigate the stability and handling of the X-15 with the lower half of the ventral fin removed, and to investigate aerodynamic boundary layer phenomena.

North American Aviation X-15 56-6671 under the right wing of a B-52 Stratofortress at 45,000 feet. (NASA)

The B-52 mothership dropped Jack McKay and the X-15 right on schedule at 10:23:07.0 a.m., local time, from an altitude of 45,000 feet (13,716 meters) and speed of approximately 450 knots (833 kilometers per hour). McKay advanced the throttle to ignite the Reaction Motors XLR99-RM-1 rocket engine. It fired immediately but when McKay advanced the throttle for the full 57,000 pounds of thrust, the engine remained at just 30%.

The X-15 could have flown back to Edwards Air Force Base, about 200 miles (320 kilometers) to the south, but with the engine not responding to the throttle, it was uncertain that it would continue running. The decision was made to make an emergency landing at Mud Lake.

Having reached a peak altitude of 53,950 feet (16,444 meters) and Mach 1.49 (1,109 miles per hour/1,785 kilometers per hour), Jack McKay continued to circle the lake burning off propellants as he lost altitude. The engine was shut down at 70.5 seconds. McKay positioned the aircraft for landing as he continued to dump unused propellant and liquid oxygen, but a considerable amount remained on board.

As he neared touchdown, he tried to lower the flaps but they did not deploy. The X-15 touched down on the dry lake bed at 296 miles per hour (476.4 kilometers per hour), 66 miles per hour (106 kilometers per hour) faster than normal.

Duration of the flight from air launch to touchdown was 6 minutes, 31.1 seconds.

The high speed and extra weight caused the X-15’s rear skids to hit harder than normal. When the nose wheels hit, a rebound effect placed even higher loads on the rear struts. At the same time, with the elevators in an extreme nose-up position, the higher aerodynamic loads pushed the skids deeper into the lake bed. This higher loading caused the left rear strut to collapse. The X-15 rolled to the left and the left elevator dug into the lake bed. This caused the aircraft to start sliding to the left. Jack McKay jettisoned the canopy and as the right wing tip dug into the surface, the X-15 flipped over and came to rest upside down.

A Piasecki H-21 rescue helicopter lands near the overturned X-15 at Mud Lake, 9 November 1961. (NASA)

The X-15 rolled over when the left landing skid collapsed because of the high-speed, overweight emergency landing at Mud Lake, Nevada. Jack McKay was trapped in the cockpit and suffered serious spinal injuries. (NASA)

The Number Two X-15, 56-6671, lies upside down and severely damaged at Mud Lake, Nevada, 9 November 1962. (NASA)

McKay was seriously injured. He was trapped in the upside down X-15 and was in danger from the vapors of the ammonia propellants and liquid oxygen. An H-21 rescue helicopter hovered overhead to blow the vapor away.

Prior to the flight, an Air Force C-130 had brought a fire engine and crew to standby at Mud Lake, returned to Edwards and picked up a second fire engine and its crew, then remained airborne should an emergency landing be made at another intermediate dry lake.

These propositioned emergency assets were able to rescue McKay and to transport him to the hospital back at Edwards.

McKay eventually recovered sufficiently to return to flight status, but ultimately his injuries forced him to retire.

The Number Two X-15 was severely damaged. It was taken back to North American and was rebuilt into the X-15A-2, intended to reach speeds up to Mach 8. It would be more than a year and a half before it flew again.

North American Aviation X-15A-2 56-6671, after a 19-month repair, redesign and modification program. The fuselage was lengthened, additional propellant and reaction control tanks installed internally, the nose wheel and rear landing skid struts lengthened, and external tanks installed. (NASA)

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