Template:Short description Template:Redirect Template:Use dmy dates Template:Use American English Template:Infobox aircraft
The North American X-15 is a hypersonic rocket-powered aircraft which was operated by the United States Air Force and the National Aeronautics and Space Administration (NASA) as part of the X-plane series of experimental aircraft. The X-15 set speed and altitude records in the 1960s, crossing the edge of outer space and returning with valuable data used in aircraft and spacecraft design. The X-15's highest speed, Template:Convert,<ref name="nasa20140228">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> was achieved on 3Template:SpacesOctober 1967,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> when William J. Knight flew at MachTemplate:Spaces6.7 at an altitude of Template:Convert, or 19.34Template:Spacesmiles. This set the official world record for the highest speed ever recorded by a crewed, powered aircraft, which remains unbroken.<ref name="Fastest">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
During the X-15 program, 12Template:Spacespilots flew a combined 199Template:Spacesflights.<ref name="nasa20140228" /> Of these, 8Template:Spacespilots flew a combined 13Template:Spacesflights which met the Air Force spaceflight criterion by exceeding the altitude of Template:Convert, thus qualifying these pilots as being astronauts; of those 13Template:Spacesflights, two (flown by the same civilian pilot) met the FAI definition (Template:Convert) of outer space. The 5Template:SpacesAir Force pilots qualified for military astronaut wings immediately, while the 3Template:Spacescivilian pilots were eventually awarded NASA astronaut wings in 2005, 35Template:Spacesyears after the last X-15 flight.Template:Sfn<ref name="NASA">Template:Cite press release</ref>
Design and developmentEdit
The X-15 was based on a concept study from Walter Dornberger for the National Advisory Committee for Aeronautics (NACA) of a hypersonic research aircraft.Template:Sfn The requests for proposal (RFPs) were published on 30Template:SpacesDecember 1954 for the airframe and on 4Template:SpacesFebruary 1955 for the rocket engine. The X-15 was built by two manufacturers: North American Aviation was contracted for the airframe in November 1955, and Reaction Motors was contracted for building the engines in 1956.
Like many X-series aircraft, the X-15 was designed to be carried aloft and drop launched from under the wing of a B-52 mother ship. Air Force NB-52A, "The High and Mighty One" (serial 52-0003), and NB-52B, "The Challenger" (serial 52-0008, also known as Balls 8) served as carrier planes for all X-15 flights. Release of the X-15 from NB-52A took place at an altitude of about Template:Convert (45,000 feet) and a speed of about Template:Convert.<ref name="E-4942">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The X-15 fuselage was long and cylindrical, with rear fairings that flattened its appearance, and thick, dorsal and ventral wedge-fin stabilizers. Parts of the fuselage (the outer skin<ref name=NASA-FS>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>) were heat-resistant nickel alloy (Inconel-XTemplate:Spaces750).Template:Sfn The retractable landing gear comprised a nose-wheel carriage and two rear skids. The skids did not extend beyond the ventral fin, which required the pilot to jettison the lower fin just before landing. The lower fin was recovered by parachute.
Cockpit and pilot systemsEdit
The X-15 was the product of developmental research, and changes were made to various systems over the course of the program and between the different models. The X-15 was operated under several different scenarios, including attachment to a launch aircraft, drop, main engine start and acceleration, ballistic flight into thin air/space, re-entry into thicker air, unpowered glide to landing, and direct landing without a main-engine start. The main rocket engine operated only for a relatively short part of the flight but boosted the X-15 to its high speeds and altitudes. Without the main rocket engine thrust, the X-15's instruments and control surfaces remained functional, but the aircraft could not maintain altitude.
As the X-15 also had to be controlled in an environment where there was too little air for aerodynamic flight control surfaces, it had a reaction control system (RCS) that used rocket thrusters.<ref name=paul /> There were two different X-15 pilot control setups: one used three joysticks, the other, one joystick.<ref name=jarvis />
The X-15 type with multiple control sticks for the pilot placed a traditional center stick between a left 3-axis joystick that sent commands to the Reaction Control System,<ref name=paul2 /> and a third joystick on the right used during high-G maneuvers to augment the center stick.<ref name=paul2 /> In addition to pilot input, the X-15 "Stability Augmentation System" (SAS) sent inputs to the aerodynamic controls to help the pilot maintain attitude control.<ref name=paul2 /> The Reaction Control System (RCS) could be operated in two modes – manual and automatic.<ref name=jarvis /> The automatic mode used a feature called "Reaction Augmentation System" (RAS) that helped stabilize the vehicle at high altitude.<ref name=jarvis>Template:Cite book</ref> The RAS was typically used for approximately three minutes of an X-15 flight before automatic power off.<ref name=jarvis />
The alternative control setup used the MH-96 flight control system, which allowed one joystick in place of three and simplified pilot input.<ref name=goleta>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The MH-96 could automatically blend aerodynamic and rocket controls, depending on how effective each system was at controlling the aircraft.<ref name=goleta />
Among the many controls were the rocket engine throttle and a control for jettisoning the ventral tail fin.<ref name=paul2 /> Other features of the cockpit included heated windows to prevent icing and a forward headrest for periods of high deceleration.<ref name=paul2 />
The X-15 had an ejection seat designed to operate at speeds up to Template:Convert and/or Template:Convert (23 miles) altitude, although it was never used during the program.<ref name=paul2>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In the event of ejection, the seat was designed to deploy fins, which were used until it reached a safer speed/altitude at which to deploy its main parachute.<ref name=paul2 /> Pilots wore pressure suits, which could be pressurized with nitrogen gas.<ref name=paul2 /> Above Template:Convert altitude, the cockpit was pressurized to Template:Convert with nitrogen gas, while oxygen for breathing was fed separately to the pilot.<ref name=paul2 />
PropulsionEdit
The initial 24 powered flights used two Reaction Motors XLR11 liquid-propellant rocket engines, enhanced to provide a total of Template:Convert of thrust as compared to the Template:Convert that a single XLR11 provided in 1947 to make the Bell X-1 the first aircraft to fly faster than the speed of sound. The XLR11 used ethyl alcohol and liquid oxygen.
By November 1960, Reaction Motors delivered the XLR99 rocket engine, generating Template:Convert of thrust. The remaining 175Template:Spacesflights of the X-15 used XLR99 engines, in a single engine configuration. The XLR99 used anhydrous ammonia and liquid oxygen as propellant, and hydrogen peroxide to drive the high-speed turbopump that delivered propellants to the engine.<ref name=paul /> It could burn Template:Convert of propellant in 80Template:Spacesseconds;<ref name=paul /> Jules Bergman titled his book on the program Ninety Seconds to Space to describe the total powered flight time of the aircraft.<ref name="gale196110">Template:Cite magazine</ref>
The X-15 reaction control system (RCS), for maneuvering in the low-pressure/density environment, used high-test peroxide (HTP), which decomposes into water and oxygen in the presence of a catalyst and could provide a specific impulse of Template:Convert.<ref name="jarvis" />Template:Sfn The HTP also fueled a turbopump for the main engines and auxiliary power units (APUs).<ref name=paul>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Additional tanks for helium and liquid nitrogen performed other functions; the fuselage interior was purged with helium gas, and liquid nitrogen was used as coolant for various systems.<ref name=paul />
Wedge tail and hypersonic stabilityEdit
The X-15 had a thick wedge tail to enable it to fly in a steady manner at hypersonic speeds.<ref name="wendell">Template:Cite book</ref> This produced a significant amount of base drag at lower speeds;<ref name=wendell /> the blunt end at the rear of the X-15 could produce as much drag as an entire F-104 Starfighter.<ref name="wendell" />
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A wedge shape was used because it is more effective than the conventional tail as a stabilizing surface at hypersonic speeds. A vertical-tail area equal to 60 percent of the wing area was required to give the X-15 adequate directional stability.{{#if:Wendell H. StillwellX-15 Research Results (SP-60)|{{#if:|}}
— {{#if:|, in }}Template:Comma separated entries}}
{{#invoke:Check for unknown parameters|check|unknown=Template:Main other|preview=Page using Template:Blockquote with unknown parameter "_VALUE_"|ignoreblank=y| 1 | 2 | 3 | 4 | 5 | author | by | char | character | cite | class | content | multiline | personquoted | publication | quote | quotesource | quotetext | sign | source | style | text | title | ts }} Stability at hypersonic speeds was aided by side panels that could be extended from the tail to increase the overall surface area, and these panels doubled as air brakes.<ref name="wendell" />
Operational historyEdit
Before 1958, United States Air Force (USAF) and NACA officials discussed an orbital X-15 spaceplane, the X-15B that would launch into outer space from atop an SM-64 Navaho missile. This was canceled when the NACA became NASA and adopted Project Mercury instead.
By 1959, the Boeing X-20 Dyna-Soar space-glider program was to become the USAF's preferred means for launching military crewed spacecraft into orbit. This program was canceled in the early 1960s before an operational vehicle could be built.Template:Sfn Various configurations of the Navaho were considered, and another proposal involved a Titan I stage.<ref name=wade/>
Three X-15s were built, flying 199Template:Spacestest flights, the last on 24Template:SpacesOctober 1968.
The first X-15 flight was an unpowered glide flight by Scott Crossfield, on 8Template:SpacesJune 1959. Crossfield also piloted the first powered flight on 17Template:SpacesSeptember 1959, and his first flight with the XLR-99 rocket engine on 15Template:SpacesNovember 1960. Twelve test pilots flew the X-15. Among these were Neil Armstrong, later a NASA astronaut and the first man to set foot on the Moon, and Joe Engle, later a commander of NASA Space Shuttle missions.
In a 1962 proposal, NASA considered using the B-52/X-15 as a launch platform for a Blue Scout rocket to place satellites weighing up to Template:Convert into orbit.<ref name="wade">Template:Cite encyclopedia</ref><ref name="cis20120321">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
In July and August 1963, pilot Joe Walker exceeded Template:Nowrap in altitude, joining NASA astronauts and Soviet cosmonauts as the first human beings to cross that line on their way to outer space. The USAF awarded astronaut wings to anyone achieving an altitude of Template:Convert, while the FAI set the limit of space at Template:Convert.
On 15Template:SpacesNovember 1967, U.S. Air Force test pilot Major Michael J. Adams was killed during X-15 Flight 191 when X-15-3, Template:Nowrap, entered a hypersonic spin while descending, then oscillated violently as aerodynamic forces increased after re-entry. As his aircraft's flight control system operated the control surfaces to their limits, acceleration built to Template:Convert vertical and Template:Convert lateral. The airframe broke apart at Template:Convert altitude, scattering the X-15's wreckage across Template:Convert. On 8Template:SpacesMay 2004, a monument was erected at the cockpit's locale, near Johannesburg, California.<ref name="xpress2004">Template:Cite journal</ref> Major Adams was posthumously awarded Air Force astronaut wings for his final flight in X-15-3, which had reached an altitude of Template:Convert. In 1991, his name was added to the Astronaut Memorial.<ref name="xpress2004" />
The second plane, X-15-2, was rebuilt <ref>Template:Harvnb</ref> after a landing accident on 9Template:SpacesNovember 1962 which damaged the craft and injured its pilot, John McKay.<ref>Template:Harvnb</ref> The new plane renamed X-15A-2, had a new 28 -in. fuselage extension to carry liquid hydrogen.<ref name="nasa20140228" /> It was lengthened by Template:Convert, had a pair of auxiliary fuel tanks attached beneath its fuselage and wings, and a complete heat-resistant ablative coating was added. It took flight for the first time on 25Template:SpacesJune 1964. It reached its maximum speed of Template:Convert in October 1967 with pilot William "Pete" Knight of the U.S. Air Force in control.
Five principal aircraft were used during the X-15 program: three X-15 planes and two modified "nonstandard" NB-52 bombers:
- Template:Nowrap 56-6670, 81 free flights
- Template:Nowrap 56-6671, 31 free flights as X-15-2, 22 free flights as X-15A-2; 53 in total
- Template:Nowrap 56-6672, 65 free flights, including the Flight 191 disaster
- Template:Nowrap 52-003 nicknamed The High and Mighty One (retired in October 1969)
- Template:Nowrap 52-008 nicknamed The Challenger, later Balls 8 (retired in November 2004)
Additionally, F-100, F-104 and F5D chase aircraft and C-130 and C-47 transports supported the program.<ref>Template:Cite book</ref>
The 200th flight over Nevada was first scheduled for 21Template:SpacesNovember 1968, to be flown by William "Pete" Knight. Numerous technical problems and outbreaks of bad weather delayed this proposed flight six times, and it was permanently canceled on 20Template:SpacesDecember 1968. This X-15 (56-6670) was detached from the B-52 and then put into indefinite storage. The aircraft was later donated to the Smithsonian Air & Space Museum for display.
- Boeing NB-52A carrying X-15.jpg
NB-52A (s/n 52-003), permanent test variant, carrying an X-15, with mission markings; horizontal X-15 silhouettes denote glide flights, diagonal silhouettes denote powered flights.
- X-15 launched bw.jpg
X-15 just after release
- NorthAmericanX-15600.jpeg
X-15 touching down on its skids, with the lower ventral fin jettisoned.
- X15A2 with tanks.jpg
X-15A-2 (56-6671) with external fuel tanks
- X-15 profiles (English).jpg
X-15 profiles
- X-15A2 2.jpg
X-15A-2 with pink ablative coating before being covered with white sealant
Aircraft on displayEdit
Both surviving X-15s are currently on display at museums in the United States. In addition, three mockups and both B-52 Stratofortresses used as motherships are on display as well.
- X-15-1 (AF Ser. No. 56-6670) is on display in the National Air and Space Museum "Milestones of Flight" gallery, Washington, D.C., but is currently undergoing conservation work at the Mary Baker Engen Restoration Hangar in the Steven F. Udvar-Hazy Center.
- X-15A-2 (AF Ser. No. 56-6671) is at the National Museum of the United States Air Force, at Wright-Patterson Air Force Base, near Dayton, Ohio. It was retired to the museum in October 1969.Template:Sfn The aircraft is displayed in the museum's Research and Development Gallery alongside other "X-planes", including the Bell X-1B and Douglas X-3 Stiletto.
MockupsEdit
- Dryden Flight Research Center, Edwards AFB, California, United States (painted with Template:Nowrap)
- Pima Air & Space Museum, adjacent to Davis-Monthan AFB, Tucson, Arizona (painted with Template:Nowrap)
- Evergreen Aviation & Space Museum, McMinnville, Oregon (painted with Template:Nowrap). A full-scale wooden mockup of the X-15, it is displayed along with one of the rocket engines.
Stratofortress mother shipsEdit
- NB-52A (AF Ser. No. 52-003) is displayed at the Pima Air & Space Museum adjacent to Davis–Monthan AFB in Tucson, Arizona. It launched the X-15-1 30Template:Spacestimes, the X-15-2, 11Template:Spacestimes, and the X-15-3 31Template:Spacestimes (as well as the M2-F2 four times, the HL-10 11Template:Spacestimes and the X-24A twice).
- NB-52B (AF Ser. No. 52-008) is on permanent display outside the north gate of Edwards AFB, California. It launched the majority of X-15 flights.
Record flightsEdit
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Highest flightsEdit
During 13 of the 199 total X-15 flights, eight pilots flew above Template:Convert, thereby qualifying as astronauts according to the US Armed Forces definition of the space border. All five Air Force pilots flew above 50Template:Spacesmiles and were awarded military astronaut wings contemporaneously with their achievements, including Adams, who received the distinction posthumously following the flightTemplate:Spaces191 disaster.<ref>Jenkins (2000), Appendix 8, p. 117.</ref> However the other three were NASA employees and did not receive a comparable decoration at the time. In 2004, the Federal Aviation Administration conferred its first-ever commercial astronaut wings on Mike Melvill and Brian Binnie, pilots of the commercial SpaceShipOne, another spaceplane with a flight profile comparable to the X-15's. Following this in 2005, NASA retroactively awarded its civilian astronaut wings to Dana (then living), and to McKay and Walker (posthumously).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Forrest S. Petersen, the only Navy pilot in the X-15 program, never took the aircraft above the requisite altitude and thus never earned astronaut wings.
Of the thirteen flights, only Template:NowrapTemplate:Tspflights 90 and 91, piloted by Template:NowrapTemplate:Tspexceeded the Template:Convert altitude used by the FAI to denote the Kármán line.
† fatal
Fastest recorded flightsEdit
| Flight | Date | Top speedTemplate:Efn | Altitude | Pilot |
|---|---|---|---|---|
| Flight 188 | 3 October 1967 | Template:Convert (Mach 6.70) | Template:Convert | William J. "Pete" Knight |
| Flight 175 | 18 November 1966 | Template:Convert (Mach 6.33) | Template:Convert | William J. "Pete" Knight |
| Flight 59 | 27 June 1962 | Template:Convert (Mach 5.92) | Template:Convert | Joseph A. Walker |
| Flight 45 | 9 November 1961 | Template:Convert (Mach 6.04) | Template:Convert | Robert M. White |
| Flight 97 | 5 December 1963 | Template:Convert (Mach 6.06) | Template:Convert | Robert A. Rushworth |
| Flight 64 | 26 July 1962 | Template:Convert (Mach 5.74) | Template:Convert | Neil A. Armstrong |
| Flight 137 | 22 June 1965 | Template:Convert (Mach 5.64) | Template:Convert | John B. McKay |
| Flight 89 | 18 July 1963 | Template:Convert (Mach 5.63) | Template:Convert | Robert A. Rushworth |
| Flight 86 | 25 June 1963 | Template:Convert (Mach 5.51) | Template:Convert | Joseph A. Walker |
| Flight 105 | 29 April 1964 | Template:Convert (Mach 5.72) | Template:Convert | Robert A. Rushworth |
PilotsEdit
- X-15 Pilots - GPN-2000-000143.jpg
The X-15 flight crew, left to right: Air Force Captain Joseph H. Engle, Air Force Major Robert A. Rushworth, NASA pilot John B. "Jack" McKay, Air Force Major William J. "Pete" Knight, NASA pilot Milton O. Thompson, and NASA pilot William H. Dana.
- X-15 Pilots.jpg
The X-15 pilots clown around in front of the #2 aircraft. From left to right: Joseph Engle, Robert Rushworth, John McKay, William Knight, Milton Thompson, and William Dana.
| Pilot | Organization | Year assigned to X-15<ref name="whoswho">Template:Cite book</ref><ref name=X15FlightLog>{{#invoke:citation/CS1|citation |
CitationClass=web
}}</ref> |
Total flights |
USAF space flights |
FAI space flights |
Max Mach |
Max speed (mph) |
Max altitude (miles) |
|---|---|---|---|---|---|---|---|---|---|
| Michael J. Adams† | U.S. Air Force | 1966 | 7 | 1 | 0 | 5.59 | 3,822 | 50.3 | |
| Neil A. Armstrong | NASA | citation | CitationClass=web
}}</ref> |
7 | 0 | 0 | 5.74 | 3,989 | 39.2 |
| Scott Crossfield | North American Aviation | 1959 | 14 | 0 | 0 | 2.97 | 1,959 | 15.3 | |
| William H. Dana | NASA | 1965 | 16 | 2 | 0 | 5.53 | 3,897 | 58.1 | |
| Joe H. Engle | U.S. Air Force | 1963 | 16 | 3 | 0 | 5.71 | 3,887 | 53.1 | |
| William J. Knight | U.S. Air Force | 1964 | 16 | 1 | 0 | 6.7 | 4,519 | 53.1 | |
| John B. McKay | NASA | 1960 | 29 | 1 | 0 | 5.65 | 3,863 | 55.9 | |
| Forrest S. Petersen | U.S. Navy | 1958 | 5 | 0 | 0 | 5.3 | 3,600 | 19.2 | |
| Robert A. Rushworth | U.S. Air Force | 1958 | 34 | 1 | 0 | 6.06 | 4,017 | 53.9 | |
| Milton O. Thompson | NASA | 1963 | 14 | 0 | 0 | 5.48 | 3,723 | 40.5 | |
| Joseph A. Walker†† | NASA | citation | CitationClass=web
}}</ref> |
25 | 3 | 2 | 5.92 | 4,104 | 67.0 |
| Robert M. White | U.S. Air Force | 1957 | 16 | 1 | 0 | 6.04 | 4,092 | 59.6 |
† Killed in the crash of X-15-3
†† Died in a group formation accident on 8 June 1966.
SpecificationsEdit
Other configurations include the Reaction Motors XLR11 equipped X-15, and the long version.
In popular cultureEdit
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See alsoEdit
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NotesEdit
ReferencesEdit
BibliographyEdit
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External linksEdit
NASAEdit
- X-15: Hypersonic Research at the Edge of Space
- Hypersonics Before the Shuttle: A Concise History of the X-15 Research Airplane
- Template:Internet Archive short film
Non-NASAEdit
- X-15A at Encyclopedia Astronautica
- X-15: Advanced Research Airplane, design summary by North America Aviation
Template:North American X-15 Template:North American Aviation aircraft Template:X-planes {{#invoke:Navbox|navbox}} Template:Navboxes