Credit: NASA. 9,083 bytes. 337 x 198 pixels.
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| X-15 in flight - Credit: NASA. 9,083 bytes. 337 x 198 pixels. |
The X-15 was the USAF and NASA project for manned spaceflight, initiated years before Mercury. The X-15 was to explore the problems of ballistic flight, winged reentry, and gliding recovery from space. It was a stepping stone to later developments - either an X-15 launched atop Navaho G-26 boosters, an X-15 scramjet version, or the X-20 - that would lead to manned orbital spaceflight. This stepping-stone approach was abandoned and the crash programs of Mercury and Apollo initiated instead, using ballistic capsules for crew recovery. Once these projects were over America returned to its original course and developed the winged space shuttle as its manned spacecraft.
In the joint X-15 hypersonic research program that NASA conducted with the Air Force, the Navy, and North American Aviation, Inc., the aircraft flew over a period of nearly 10 years and set the world's unofficial speed and altitude records of 4,520 mph (Mach 6.7) and 354,200 ft in a program to investigate all aspects of piloted hypersonic flight. Information gained from the highly successful X-15 program contributed to the development of the Mercury, Gemini, and Apollo piloted spaceflight programs as well as the Space Shuttle program.
Manufactured by North American Aviation, Inc., three rocket-powered X-15's flew a total of 199 times, with North American (and former National Advisory Committee for Aeronautics or NACA) pilot Scott Crossfield making the first, unpowered glide flight on June 8, 1959. NASA's William H. Dana was the pilot for the final flight in the program on Oct. 24, 1968. All of these flights took place within what was called the "High Range" surrounding but mostly to the east of Edwards Air Force Base, CA, and NASA's Flight Research Center (later called the NASA Dryden Flight Research Center).
There were ten other pilots in the program for a total of twelve: five from NASA, five from the Air Force, one from the Navy, and one, Crossfield, from North American. Generally, pilots used one of two types of flight profiles a speed profile that called for the pilot to maintain a level altitude until time for descent to a landing, and a high-altitude flight plan that required maintaining a steep rate of climb until reaching altitude and then decending.
Because of the large fuel consumption of its rocket engine, the X-15 was air launched from a B-52 aircraft at about 45,000 ft and speeds upward of 500 mph. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 seconds of flight. The remainder of the normal 8- to 12-minute flight was without power and ended in a 200-mph glide landing. Because the nose landing wheel lacked steering and the main landing gear employed skids, the X-15 had to land on a dry lakebed. The Rogers Dry Lake adjacent to Edwards and Dryden was the intended landing location for all flights, but there were numerous emergency lakebeds selected in advance for emergency landings.
Design
The X-15 was a follow-on research aircraft to the early X-planes, which had explored the flight regime from just below the speed of sound (Mach 1) to Mach 3.2. In 1952 the NACA had begun preliminary research into space flight and associated problems. Two years later, NACA's Research Airplane Projects Panel discussed the need for a new research airplane to study hypersonic and space flight. The NACA established the characteristics of what became the X-15 and presented them to the Air Force and Navy in July 1954. The two services and NACA signed a memorandum of understanding for the joint project in Dec. 1954, and the Air Force selected North American to develop three X-15 research aircraft in Sept.1955.
A North American team headed by Chief Project Engineer Charles Feltz designed the aircraft, with technical guidance from the NACA's Langley Aeronautical Laboratory (later NASA's Langley Research Center) and High-Speed Flight Station (as Dryden was then called).
Although the number two aircraft was later modified, the basic X-15 was a single-seat, mid-wing monoplane designed to explore the areas of high aerodynamic heating rates, stability and control, physiological phenomena, and other problems relating to hypersonic flight (above Mach 5). Because the Reaction Motors Division of Thiokol Chemical Corp. did not have the throttleable XLR-99 engine ready for the early flights of the aircraft, the X-15 initially flew with two XLR-11 engines, producing a thrust of 16,380 lb. Once the XLR-99 was installed, the thrust became 57,000 lb.
The X-15 used conventional aerodynamic controls for flight in the dense air of the usable atmosphere. The controls consisted of rudder surfaces on the vertical stabilizers to control yaw (movement of the nose left or right) and canted horizontal surfaces on the tail to control pitch (nose up and down) when moving in synchronization or roll when moved differentially.
For flight in the thin air outside the Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets on the nose of the aircraft provided pitch and yaw control. Those on the wings furnished roll control.
The outer skin of the X-15 consisted of a nickel-chrome alloy called Inconel X, employed in a heat sink structure to withstand the results of aerodynamic heating when the aircraft was flying within the atmosphere. The cabin was made of aluminum and was isolated from the outer structure to keep it cool.
Program History
The first X-15 arrived at the NASA High-Speed Flight Station in the early months of 1959, and Scott Crossfield, who had helped with the design of the aircraft, soon began the contractor demonstration flights. During its research program, the aircraft set unofficial world speed and altitude records of 4,520 mph (Mach 6.7 on Oct. 3, 1967, with Air Force pilot Pete Knight at the controls) and 354,200 ft (on Aug. 22, 1963, with NASA pilot Joseph Walker in the cockpit).
More important than records, however, were the X-15's probing of hypersonic aerodynamic performance and heating rates, research into structural behavior during high heating and high flight loads, study of hypersonic stability and control during exit from and reentry of the atmosphere, and examination of pilot performance and physiology.
In the course of its flight research, the X-15's pilots and instrumentation yielded data for more than 765 research reports. As Dryden Chief Scientist Ken Iliff and his wife, aerospace research engineer Mary Shafer, have written, "The aircraft returned benchmark hypersonic data for aircraft performance, stability and control, materials, shock interaction, hypersonic turbulent boundary layer, skin friction, reaction control jets, aerodynamic heating, and heat transfer." (The boundary layer is the thin layer of air next to the body of the aircraft that has distinctive flow characteristics because of friction between the air and the surface of the aircraft; control of the flow in the boundary layer is critical to improving aircraft performance.)
The distinguished Langley aeronautical researcher John Becker, who had been an early advocate of the X-15 program, identified 25 specific accomplishments of the effort.
These included:
First application of hypersonic theory and wind tunnel work to an actual flight vehicle. First use of reaction controls for attitude control in space. First reusable superalloy structure capable of with- standing the temperatures and thermal gradients of hypersonic reentry. Development of (a servo-actuated ball) nose flow direction sensor for operation over an extreme range of dynamic pressure and a stagnation air temperature of 1,900� F (for accurate measurement of air speed and flow angle at supersonic and hypersonic speeds). Development of the first practical full pressure suit for pilot protection in space. Development of inertial flight data systems capableof functioning in a high dynamic pressure and space environment. Discovery that hypersonic boundary layer flow is turbulent and not laminar. Discovery that turbulent heating rates are significantly lower than had been predicted by theory. First direct measurement of hypersonic aircraft skin friction and discovery that skin friction is lower than had been predicted. Discovery of hot spots generated by surface irregularities. (These last four discoveries led to improved design tools for future hypersonic vehicles, including the Space Shuttle.) Discovery of methods to correlate base drag measurements with tunnel test results so as to correct wind tunnel data (and thereby improve design criteria for future air-and spacecraft). Demonstration of a pilot's ability to control a rocket boosted aerospace vehicle through atmospheric exit. Successful transition from aerodynamic controls to reaction controls and back again. First application of energy-management techniques(for the positioning of the vehicle for landing; these were essential for the landing of the Space Shuttle and all future reusable launch vehicles following their reentry from space.) Use of the three X-15 aircraft as testbeds to carry a wide variety of experimental packages.
These experiments -28 of them- ranged from astronomy to micrometeorite collection. They included tests of horizon definition and proposed insulation that bore fruit in the navigation equipment and thermal protection used on the Saturn launch vehicles in the Apollo program, which dispatched 12 astronauts to the moon and back. Among the 12 was Neil Armstrong, the first human to step on the moon's surface and a former X-15 pilot who also flew many other research aircraft at the Flight Research Center.
In the area of physiology, researchers learned that the heart rates of X-15 pilots ranged from 145 to 185 beats per minute during flight. This greatly exceeded the normal 70 to 80 beats per minute experienced on test missions for other aircraft. The cause of the difference proved to be the stress X-15 pilots encountered during prelaunch in anticipation of each mission. As it turned out, the higher rates proved typical for the future physiological behavior of pilot- astronauts.
More intangibly but no less importantly, in the words of John Becker, the X-15 project led to "the acquisition of new piloted aerospace flight 'know how' by many teams in government and industry. They had to learn to work together, face up to unprecedented problems, develop solutions, and make this first manned [today, we would say piloted] aerospace project work. These teams were an important national asset in the ensuing space programs."
 | X-15 with Scramjet Credit: NASA. 24,152 bytes. 387 x 155 pixels. |
The Aircraft
Except for the number two X-15 when modified as the X-15A-2, the X-15's were roughly 50 ft long, with a 22-ft wing span. The wedge-shaped vertical tail was 13 ft high. Because the lower vertical tail extended below the landing skids when they were deployed, a part of the lower vertical tail was jettisoned just before landing and recovered by a parachute. The aircraft was powered by a Thiokol (Reaction Motors Division) XLR-99 throttleable rocket engine powered by anhydrous ammonia and liquid oxygen. It provided a maximum thrust of 57,000 lb and a minimum thrust of 28,000 lb. Launch weight of the aircraft was 31,275 lb, decreasing to 12,295 lb at burnout.
The X-15A-2, modified from the number two aircraft and delivered to NASA in February 1964, included among other new features, a 28-in. fuselage extension to carry liquid hydrogen for a supersonic combustion ramjet that was flown (as a dummy) but never tested. It also had external tanks for liquid ammonia and liquid oxygen. These tanks provided roughly 60 seconds of additional engine burn and were used on the aircraft's Mach 6.7 flight. While adding to the speed the X-15 did achieve, the tanks also increased the aircraft's weight to almost 57,000 lb and added significantly to the drag experienced by the aircraft in flight.
Pilots
X-15 pilots in order by dates of first flights # of Flights
A. Scott Crossfield, North American Aviation 14
Joseph A. Walker, NASA 25
Robert M. White, United States Air Force (USAF) 16
Forrest S. Petersen, United States Navy 05
John B. McKay, NASA 29
Robert A. Rushworth, USAF 34
Neil A. Armstrong, NASA 07
Joe H. Engle, USAF 16
Milton O. Thompson, NASA 14
William J. Knight, USAF 16
William H. Dana, NASA 16
Michael J. Adams, USAF 07
total 199
The X-15 had its share of emergency landings and accidents, but only two produced serious injuries or death. On Nov. 9, 1962, Jack McKay experienced an engine failure and landed at Mud Lake, NV. The landing gear collapsed, flipping him and the aircraft on its back. Although he recovered from his injuries sufficiently to fly again, he eventually had to retire because of them. On Nov. 15, 1967, on Michael Adams seventh flight, he entered a spin from which he was able to recover but could not bring it out of an inverted dive because of a technical problem with the adaptive flight control system. He died in the resultant crash of the X-15 number three.
Craft.Crew Size: 1. Design Life: .01 days. Total Length: 15.5 m. Maximum Diameter: 1.4 m. Total Mass: 30,121 kg. Total Propellants: 20,551 kg. Primary Engine Thrust: 26,762 kgf. Main Engine Propellants: Lox/Ammonia. Main Engine Isp: 239 sec. Total spacecraft delta v: 2,100 m/s. Electrical System: Batteries.
An NACA report was issued covering several projects and proposals for the flight of manned and unmanned vehicles to altitudes above the earth where atmospheric density was very low. The substance of these reports was presented at the June 24, 1952, meeting of the Committee on Aerodynamics. After the presentation, committee member Robert J. Woods recommended that basic research be initiated on the problems of space flight and stated that the NACA was the logical organization to carry on this work. To accomplish this task, a small working group was established to analyze the available information on the subject of space flight. The objective of this group was to arrive at a concept of a suitable manned test vehicle that could be constructed within 2 years.
The NACA Committee on Aerodynamics recommended that NACA increase its research efforts on the problem of manned and unmanned flight at altitudes between 12 and 50 miles and at speeds of mach 4 through 10. As a result of this recommendation, the Langley Aeronautical Laboratory began preliminary studies on this project and immediately identified several problem areas. Two of these areas were aerodynamic heating and the achievement of stability and control at very high altitudes and speeds. Of the two, Langley considered aerodynamic heating to be the more serious, and, until this problem was resolved, the design of practical spacecraft impractical.
Preliminary studies were completed by C. E. Brown, W. J. O'Sullivan, Jr., and C. H. Zimmerman at the Langley Aeronautical Laboratory relative to the study of the problems of manned space flight and a suggested test vehicle to investigate these problems. One of the possibilities considered from the outset of the effort in mid-1952 was modification of the X-2 airplane to attain greater speeds and altitudes of the order of 200,000 feet. It was believed that such a vehicle could not only resolve some of the aerodynamic heating problems, but also that the altitude objective would provide an environment with a minimum atmospheric density, representing many problems of outer space flight. However, there was already a feeling among many NACA scientists that the speed and altitude exploratory area should be raised. In fact, a resolution to this effect, presented as early as July 1952, stated that '. . . the NACA devote . . . effort to problems of unmanned and manned flights at altitudes from 50 miles to infinity and at speeds from mach 10 to the velocity of escape from the earth's gravity.' The Executive Committee of NACA actually adopted this resolution as an objective on July 14, 1952.
The NACA determined the characteristics of what later became the X-15 rocket aircraft, one of the steps to manned space flight.
The two services and NACA signed a memorandum of understanding for the joint project in Dec. 1954. In 1952 the NACA had begun preliminary research into space flight and associated problems.
After 2 years' study of problems that might be encountered in manned space flight, a joint group - NACA, Air Force, and Navy - met in Washington to discuss the need for a hypersonic research vehicle and to decide on the type of aircraft that could attain these objectives. The NACA proposal was accepted in December 1954, and a formal memorandum of understanding was signed to initiate the X-15 project. Technical direction of the project was assigned to the NACA. On November 9, 1961, the X-15 reached its design speed of over 4,000 miles per hour and achieved partial space conditions on July 17, 1962, when it reached an altitude of 314,750 feet. By the latter date, the Mercury spacecraft had made two manned orbital flights.
A North American team, headed by Chief Project Engineer Charles Feltz, designed the aircraft, with technical guidance from the NACA's Langley Aeronautical Laboratory and High-Speed Flight Station.
Details of X-15 rocket research airplane were publicly revealed for the first time.
Experience with the X-15 design indicated that many of the weight figures advanced by the Langley Aeronautical Laboratory for the drag or lift configurations of the reentry vehicle (later to become the Mercury spacecraft) were too low, according to Walter C. Williams, Chief of the NACA High-Speed Flight Station. Weights of auxiliary-power fuel, research instrumentation, and cockpit equipment as set by Langley were too low in terms of X-15 experience. Williams stated the total weight should be 2,300 pounds for the drag configuration and 2,500 pounds for the lifting configuration.
In a memorandum to Dr. James R. Killian, Jr., Special Assistant to the President for Science and Technology, Dr. Hugh L. Dryden, Director of NACA, pointed out that NASA would inherit from NACA a rich technical background, competence, and leadership in driving toward the objective of a manned satellite program. For years NACA groups had been involved in research on such items as stabilization of ultra-high speed vehicles, provision of suitable controls, high temperature structural designs, and all the problems of reentry. In fact, a part of this work had been directed specifically toward the problem of designing a manned satellite. Also, the X-15 program had provided much experience in human factors applicable to the orbital flight of man. Therefore, Dr. Dryden concluded, in consonance with the intent of the Space Act of 1958, the assignment of the program to the NACA would be consistent.
 | X-15A / F-104 - X-15A / F-104 in flight Credit: NASA. 25,446 bytes. 373 x 188 pixels. |
First of a series of three X-15 experimental rocket-powered manned research aircraft was rolled out at the Los Angeles plant of North American Aviation, Inc., in the joint USAF-USN-NASA program.
First flight for X-15 # 1. Planned glide flight. Maximum Speed - 840 kph. Maximum Altitude - 11445 m.
First flight for X-15 # 2. First powered flight. Maximum Speed - 2241 kph. Maximum Altitude - 15954 m. Turbopump case failure resulted in fire in engine compartment.
Maximum Speed - 2283 kph. Maximum Altitude - 18831 m. Nose gear door failed on landing.
Engine fire; fuselage structural failure on landing. Aircraft returned to North American for rebuild. Maximum Speed - 1062 kph. Maximum Altitude - 13857 m.
Maximum Speed - 2685 kph. Maximum Altitude - 20374 m.
Maximum Speed - 2359 kph. Maximum Altitude - 26858 m.
Maximum Speed - 1667 kph. Maximum Altitude - 16045 m. Automatic shutdown of one chamber in upper XLR-11.
Maximum Speed - 2283 kph. Maximum Altitude - 16045 m. 6G maneuver test.
Maximum Speed - 2124 kph. Maximum Altitude - 14822 m. Roll damper malfunctioned.
Maximum Speed - 2080 kph. Maximum Altitude - 15235 m.
Maximum Speed - 2156 kph. Maximum Altitude - 15653 m. 3.5 to 5G pullouts to simulate reentry.
Maximum Speed - 2018 kph. Maximum Altitude - 14630 m.
Maximum Speed - 2718 kph. Maximum Altitude - 18134 m.
Maximum Speed - 2336 kph. Maximum Altitude - 18574 m.
Maximum Speed - 3397 kph. Maximum Altitude - 23738 m.
Maximum Speed - 2558 kph. Maximum Altitude - 33222 m.
Maximum Speed - 2336 kph. Maximum Altitude - 15631 m. First test of reaction control system.
Maximum Speed - 3533 kph. Maximum Altitude - 23809 m. Unofficial world speed record. This topped Captain Apt's speed of 2,094 mph attained in the X-2 on September 27, 1956.
Maximum Speed - 2851 kph. Maximum Altitude - 41605 m. Established a new altitude record for a manned vehicle of 136,500 feet. This topped Captain Kincheloe's record altitude of 126,200 feet attained on September 7, 1956, in the X-2 rocket research aircraft.
Maximum Speed - 3195 kph. Maximum Altitude - 23159 m.
Maximum Speed - 3510 kph. Maximum Altitude - 24343 m.
Maximum Speed - 1783 kph. Maximum Altitude - 16168 m. Premature shutdown of both XLR-11's.
Maximum Speed - 2059 kph. Maximum Altitude - 16398 m.
 | X-15 on lakebed Credit: NASA. 11,369 bytes. 492 x 148 pixels. |
Maximum Speed - 2071 kph. Maximum Altitude - 14905 m.
First flight with XLR-99 engine. Maximum Speed - 3154 kph. Maximum Altitude - 24750 m.
Maximum Speed - 2018 kph. Maximum Altitude - 16688 m. Lower XLR-11 shutdown but restarted.
First restart with XLR-99 engine. Maximum Speed - 2665 kph. Maximum Altitude - 18867 m.
Maximum Speed - 1858 kph. Maximum Altitude - 14886 m. Only 7 of 8 XLR-11 chambers ignited.
Maximum Speed - 3027 kph. Maximum Altitude - 16268 m.
First hot nose flight. Maximum Speed - 1911 kph. Maximum Altitude - 15269 m.
Maximum Speed - 1949 kph. Maximum Altitude - 15170 m.
Maximum Speed - 3660 kph. Maximum Altitude - 23820 m. Last XLR-11 flight.
Maximum Speed - 4674 kph. Maximum Altitude - 23610 m.
Maximum Speed - 4441 kph. Maximum Altitude - 51700 m.
Maximum Speed - 4946 kph. Maximum Altitude - 32000 m.
Maximum Speed - 5321 kph. Maximum Altitude - 32850 m.
Harmon International Aviator's Trophy for 1961 announced as going to three winners for the first time-X-15 rocket research airplane pilots: A. Scott Crossfield, of North American; Joseph A. Walker, of NASA, and Maj. Robert A. White, U.S. Air Force.
Maximum Speed - 5797 kph. Maximum Altitude - 32830 m. Lost cabin pressure.
Maximum Speed - 4401 kph. Maximum Altitude - 23830 m. Lost cabin pressure.
Maximum Speed - 5821 kph. Maximum Altitude - 34840 m. Smoke in cockpit due to scorching paint.
Maximum Speed - 5792 kph. Maximum Altitude - 31030 m. Test reentry heat limit. Smoke in cockpit due to scorching paint.
Flight made with lower ventral off. Maximum Speed - 4553 kph. Maximum Altitude - 23770 m.
Outer panel of left windshield cracked. Maximum Speed - 5868 kph. Maximum Altitude - 66150 m.
Maximum Speed - 6275 kph. Maximum Altitude - 33100 m.
Design speed achieved. Outer right windshield shattered. Maximum Speed - 6586 kph. Maximum Altitude - 30950 m.
First flight for X-15 # 3. Maximum Speed - 4026 kph. Maximum Altitude - 24700 m.
Emergency landing on Mud Lake after engine failed to light. Maximum Speed - 1038 kph. Maximum Altitude - 13,640 m.
 | X-15 3 View Credit: © Mark Wade. 1,359 bytes. 203 x 282 pixels. |
Maximum Speed - 4586 kph. Maximum Altitude - 54860 m. The X-15 was flown in a test of a new automatic control system to be used in the Dyna-Soar and Apollo spacecraft. The previous electronic control system had been automatic only while the X-15 was in the atmosphere; the new system was automatic in space as well.
Maximum Speed - 6220 kph. Maximum Altitude - 46940 m.
Maximum Speed - 6097 kph. Maximum Altitude - 63250 m.
Maximum Speed - 5879 kph. Maximum Altitude - 32160 m.
Design altitude flight. Maximum Speed - 5614 kph. Maximum Altitude - 75190 m.
Maximum Speed - 5670 kph. Maximum Altitude - 21460 m.
Maximum Speed - 5551 kph. Maximum Altitude - 30600 m. Roller coaster flight with 3 peaks for local airflow investigation.
Maximum Speed - 5913 kph. Maximum Altitude - 40420 m. Steepest reentry descent with highest angle of attack (27 degrees) to date.
Maximum Speed - 5908 kph. Maximum Altitude - 31580 m.
Maximum Speed - 5659 kph. Maximum Altitude - 56270 m.
Maximum Speed - 5858 kph. Maximum Altitude - 75190 m.
Unofficial world speed record. Maximum Speed - 6603 kph. Maximum Altitude - 37700 m.
Maximum Speed - 5278 kph. Maximum Altitude - 25360 m.
Maximum Speed - 5911 kph. Maximum Altitude - 32670 m.
FAI world altitude record. Maximum Speed - 6166 kph. Maximum Altitude - 95940 m. First astronaut wings flight (USAF definition).
Maximum Speed - 5590 kph. Maximum Altitude - 25680 m.
Maximum Speed - 6418 kph. Maximum Altitude - 30150 m. Roller coaster descent to simulate emergency reentry.
Maximum Speed - 5532 kph. Maximum Altitude - 44040 m.
Maximum Speed - 4735 kph. Maximum Altitude - 27700 m.
Maximum Speed - 6029 kph. Maximum Altitude - 59010 m. New reentry technique using pitch angle instrument instead of AOA.
Maximum Speed - 5686 kph. Maximum Altitude - 27000 m.
Maximum Speed - 5546 kph. Maximum Altitude - 29630 m.
This and most following flights without lower ventral. Maximum Speed - 4450 kph. Maximum Altitude - 20790 m.
Maximum Speed - 5620 kph. Maximum Altitude - 34200 m.
 | X-15 Crash scene Credit: NASA. 42,745 bytes. 551 x 280 pixels. |
Maximum Speed - 6056 kph. Maximum Altitude - 41000 m.
Engine only produced 35% power. Emergency landing at Mud Lake. Aircraft seriously damaged when gear failed. McKay injured. Maximum Speed - 1640 kph. Maximum Altitude - 16450 m.
Maximum Speed - 6021 kph. Maximum Altitude - 43100 m.
Maximum Speed - 6103 kph. Maximum Altitude - 48900 m.
First civilian flight above 80 km. Maximum Speed - 5917 kph. Maximum Altitude - 82810 m. Second astronaut wings flight (USAF definition).
Maximum Speed - 4608 kph. Maximum Altitude - 22680 m. First flight in scientific and advanced research series - carried aerial mapping camera.
Nose landing gear failed. Maximum Speed - 6066 kph. Maximum Altitude - 28190 m.
Maximum Speed - 5612 kph. Maximum Altitude - 63820 m. Carried earth background radiation instrument in support of Midas reconnsat development.
Maximum Speed - 5792 kph. Maximum Altitude - 29140 m.
Maximum Speed - 6204 kph. Maximum Altitude - 37860 m. Lost both nose landing gear tires and forward fuselage buckled after APU gear box pressure loss.
Inner panel of left windshield cracked. Maximum Speed - 6208 kph. Maximum Altitude - 28040 m.
Maximum Speed - 5694 kph. Maximum Altitude - 68180 m.
Maximum Speed - 6293 kph. Maximum Altitude - 34080 m.
Maximum Speed - 5511 kph. Maximum Altitude - 86870 m. Third astronaut wings flight (USAF definition).
Maximum Speed - 5842 kph. Maximum Altitude - 69010 m.
Maximum Speed - 6315 kph. Maximum Altitude - 31940 m.
Maximum Speed - 5969 kph. Maximum Altitude - 106010 m. Astronaut wings flight. 80 cm diameter balloon dragged on 30 m line to measure air density. First X-15 astronaut flight (FAI definition); fourth astronaut wings flight (USAF definition).
Unofficial world altitude record. Maximum Speed - 6105 kph. Maximum Altitude - 107960 m. Second X-15 astronaut flight (FAI definition); fifth astronaut wings flight (USAF definition).
Maximum Speed - 4560 kph. Maximum Altitude - 23710 m.
Maximum Speed - 4364 kph. Maximum Altitude - 22600 m.
Maximum Speed - 4706 kph. Maximum Altitude - 25080 m. First flight with sharp-edged vertical stabilizer.
Maximum Speed - 5287 kph. Maximum Altitude - 27680 m.
Maximum Speed - 5326 kph. Maximum Altitude - 27371 m.
Maximum Speed - 6465 kph. Maximum Altitude - 30785 m. Camera test in combination with U-2 flight.
Maximum Speed - 5818 kph. Maximum Altitude - 42642 m.
Maximum Speed - 5216 kph. Maximum Altitude - 21641 m.
Maximum Speed - 5821 kph. Maximum Altitude - 32736 m. First test of hypersonic speed brakes.
Maximum Speed - 5662 kph. Maximum Altitude - 23957 m.
Maximum Speed - 5458 kph. Maximum Altitude - 23165 m.
Maximum Speed - 6158 kph. Maximum Altitude - 30937 m. Secret reconn camera test.
Maximum Speed - 5580 kph. Maximum Altitude - 53340 m.
Maximum Speed - 6285 kph. Maximum Altitude - 30968 m.
Maximum Speed - 4962 kph. Maximum Altitude - 22189 m.
Maximum Speed - 5262 kph. Maximum Altitude - 59680 m.
Premature engine shutdown at 41 sec. Maximum Speed - 3001 kph. Maximum Altitude - 19568 m.
Maximum Speed - 5364 kph. Maximum Altitude - 30358 m.
Maximum Speed - 5664 kph. Maximum Altitude - 51938 m. First test of IR horizon scanner.
Maximum Speed - 5250 kph. Maximum Altitude - 23774 m. First test of various heat-resistant panels attached to fuselage.
Maximum Speed - 5688 kph. Maximum Altitude - 24750 m.
Maximum Speed - 6216 kph. Maximum Altitude - 27737 m.
Maximum Speed - 5817 kph. Maximum Altitude - 23957 m.
Maximum Speed - 6256 kph. Maximum Altitude - 29566 m.
Maximum Speed - 4904 kph. Maximum Altitude - 25878 m. First flight with X-20 INS and wing tip pods.
Maximum Speed - 5009 kph. Maximum Altitude - 25786 m.
Maximum Speed - 5990 kph. Maximum Altitude - 28164 m.
Maximum Speed - 5913 kph. Maximum Altitude - 34503 m.
Maximum Speed - 5781 kph. Maximum Altitude - 24750 m.
Maximum Speed - 5973 kph. Maximum Altitude - 30297 m. Immediately after burnout aircraft gyrated around all 3 axes for 7 seconds.
Maximum Speed - 6253 kph. Maximum Altitude - 29931 m.
Maximum Speed - 6034 kph. Maximum Altitude - 46817 m.
Maximum Speed - 5760 kph. Maximum Altitude - 31059 m.
Maximum Speed - 5760 kph. Maximum Altitude - 24293 m.
Maximum Speed - 5100 kph. Maximum Altitude - 54803 m.
Maximum Speed - 6040 kph. Maximum Altitude - 63886 m.
Maximum Speed - 5477 kph. Maximum Altitude - 74585 m.
Maximum Speed - 5697 kph. Maximum Altitude - 33071 m.
Maximum Speed - 5522 kph. Maximum Altitude - 85527 m. Astronaut wings flight (USAF definition).
Maximum Speed - 6050 kph. Maximum Altitude - 32126 m.
Maximum Speed - 5686 kph. Maximum Altitude - 31455 m.
Maximum Speed - 5712 kph. Maximum Altitude - 82601 m. Astronaut wings flight (USAF definition).
Maximum Speed - 5799 kph. Maximum Altitude - 65258 m.
Maximum Speed - 5426 kph. Maximum Altitude - 73030 m.
Maximum Speed - 5686 kph. Maximum Altitude - 29627 m.
Maximum Speed - 5662 kph. Maximum Altitude - 72847 m.
Maximum Speed - 5712 kph. Maximum Altitude - 30571 m.
Maximum Speed - 6005 kph. Maximum Altitude - 90099 m. Astronaut wings flight (USAF definition).
Maximum Speed - 4373 kph. Maximum Altitude - 23350 m.
Maximum Speed - 5001 kph. Maximum Altitude - 28770 m.
Maximum Speed - 5718 kph. Maximum Altitude - 81230 m. Astronaut wings flight (USAF definition).
Maximum Speed - 5662 kph. Maximum Altitude - 72210 m.
Maximum Speed - 4450 kph. Maximum Altitude - 24440 m.
Premature engine shutdown at 32 sec. Maximum Speed - 2307 kph. Maximum Altitude - 20850 m.
Maximum Speed - 5876 kph. Maximum Altitude - 39620 m.
Maximum Speed - 5176 kph. Maximum Altitude - 29290 m. First flight with X-20 energy management system.
Maximum Speed - 5957 kph. Maximum Altitude - 73700 m.
Maximum Speed - 6376 kph. Maximum Altitude - 40450 m.
Maximum Speed - 5776 kph. Maximum Altitude - 76500 m.
Maximum Speed - 5804 kph. Maximum Altitude - 54250 m.
Maximum Speed - 5701 kph. Maximum Altitude - 78490 m. Collected micrometeorites and extraterrestrial dust.
Premature engine shutdown at 38 sec. Maximum Speed - 2578 kph. Maximum Altitude - 22310 m.
Maximum Speed - 5770 kph. Maximum Altitude - 22980 m. JPL spectrometer measured solar flux; radiometer characterized exhaust plume in UV for reconnsat sensors; collected micrometeorites.
Maximum Speed - 4666 kph. Maximum Altitude - 22980 m. Engine shut down at 90 seconds.
Maximum Speed - 6034 kph. Maximum Altitude - 93540 m. Astronaut wings flight (USAF definition).
Maximum Speed - 5020 kph. Maximum Altitude - 28040 m.
Maximum Speed - 6150 kph. Maximum Altitude - 40570 m. Inertial system failed after peak altitude; cabin pressurization lost during descent.
Maximum Speed - 1871 kph. Maximum Altitude - 16280 m.
Maximum Speed - 5985 kph. Maximum Altitude - 50900 m.
Maximum Speed - 5112 kph. Maximum Altitude - 21670 m.
Maximum Speed - 5802 kph. Maximum Altitude - 69890 m.
Maximum Speed - 5810 kph. Maximum Altitude - 25050 m.
Electrical failure while climbing through 32610 m; lost engine at 69 seconds; landed at Mud Lake with no flaps; Knight injured while exiting aircraft. Maximum Speed - 4618 kph. Maximum Altitude - 52730 m.
Maximum Speed - 5942 kph. Maximum Altitude - 25720 m.
Maximum Speed - 5012 kph. Maximum Altitude - 25720 m.
Maximum Speed - 7270 kph. Maximum Altitude - 76530 m.
Maximum Speed - 6204 kph. Maximum Altitude - 85500 m. Astronaut wings flight (USAF definition).
Fatal accident, aircraft destroyed. After reaching peak altitude, entered spin at Mach 5. Entered dive at 30,000 m, began high frequency pitch oscillations, disintegrated when these reached 15 Gs.Maximum Speed - 5744 kph. Maximum Altitude - 81080 m.
Maximum Speed - 4631 kph. Maximum Altitude - 31850 m. Tested Saturn V insulation.
Maximum Speed - 5808 kph. Maximum Altitude - 57150 m.
Maximum Speed - 5704 kph. Maximum Altitude - 63090 m.
Maximum Speed - 5733 kph. Maximum Altitude - 67090 m.
Maximum Speed - 5442 kph. Maximum Altitude - 67510 m.
Maximum Speed - 5540 kph. Maximum Altitude - 81530 m. Astronaut wings flight (USAF definition).
Maximum Speed - 5990 kph. Maximum Altitude - 77450 m.
Last flight. Maximum Speed - 5979 kph. Maximum Altitude - 77720 m.