North American X-15: Difference between revisions

{{Short description|Rocket-powered aircraft and spaceplane operated by the US Air Force and NASA}}

{{Redirect|X-15X15}}

The '''North American X-15''' is a [[Hypersonic speed|hypersonic]] [[rocket-powered aircraft]]. It was operated by the [[United States Air Force]] and the [[NASA|National Aeronautics and Space Administration]] (NASA) as part of the [[List of X-planes|X-plane]] series of [[experimental aircraft]]. The X-15 set speed and altitude records in the 1960s, crossing the [[Kármán line|edge of outer space]] and returning with valuable data used in [[aircraft]] and [[spacecraft]] design. The X-15's highest speed, {{convert|4520|mph|km/h m/s|0}},<ref name="nasa20140228">{{cite web |url=http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-052-DFRC.html |title=NASA Armstrong Fact Sheet: X-15 Hypersonic Research Program |publisher=NASA |editor-first=Yvonne |editor-last=Gibbs |date=28 February 2014 |access-date=4 October 2015 |quote= 4,520 mph (Mach 6.7 on Oct. 3, 1967,}}</ref> [[X-15 Flight 188|was achieved on]] 3{{spaces}}October 1967,<ref>{{cite web|first1=Caroline|last1=Haskins|first2=Brian|last2=Anderson|first3=Jason|last3=Koebler|access-date=2019-02-05|title=Why the Piloted Flight Speed Record Hasn't Been Broken in 50 Years|url=https://motherboard.vice.com/en_us/article/qvj5vp/piloted-aircraft-flight-speed-record-1967-nasa-air-force-william-knight-x-15|date=6 October 2017}}</ref> when [[William J. Knight]] flew at [[Mach number|Mach]]{{spaces}}6.7 at an altitude of {{convert|102100|ft|m|sigfig=4}}, or 19.34{{spaces}}miles. This set the [[Flight airspeed record|official world record]] for the highest speed ever recorded by a crewed, powered aircraft, which remains unbroken.<ref name="Fastest">{{cite web |url=http://www.aerospaceweb.org/aircraft/research/x15/ |title=North American X-15 High-Speed Research Aircraft |work=Aerospaceweb.org |year=2010 |access-date=24 November 2008}}</ref><ref>{{cite web |url=https://www.cnn.com/style/article/x-15-rocket-aircraft/index.html |title=X-15: The fastest manned rocket plane ever |author=Jacopo Prisco |date=July 28, 2020 |work=CNN |access-date=November 12, 2020}}</ref>

During the X-15 program, 12{{spaces}}pilots flew a combined 199{{spaces}}flights.<ref name="nasa20140228" /> Of these, 8{{spaces}}pilots flew a combined 13{{spaces}}flights which met the Air Force [[human spaceflight|spaceflight]] criterion by exceeding the altitude of {{convert|50|mi|km}}, thus qualifying these pilots as being [[astronaut]]s; of those 13{{spaces}}flights, two (flown by the same civilian pilot) met the [[Fédération Aéronautique Internationale|FAI]] definition ({{convert|100|km|mi}}) of [[outer space]]. The 5{{spaces}}Air Force pilots qualified for military [[astronaut wings]] immediately, while the 3{{spaces}}civilian pilots were eventually awarded NASA astronaut wings in 2005, 35{{spaces}}years after the last X-15 flight.{{sfn|Jenkins|2001|p=10}}<ref name="NASA">{{cite press release |url=http://www.nasa.gov/home/hqnews/2005/aug/HQ_05233_X-15_pilots_honored.html |title=NASA Honors High Flying Space Pioneers |publisher=NASA |first1=Elvia H. |last1=Thompson |first2=Frederick A. |last2=Johnsen |date=23 August 2005 |id=Release 05-233 |access-date=15 September 2007 |archive-date=13 April 2018 |archive-url=https://web.archive.org/web/20180413033113/http://www.nasa.gov/home/hqnews/2005/aug/HQ_05233_X-15_pilots_honored.html |url-status=dead }}</ref>

The X-15 was based on a concept study from [[Walter Dornberger]] for the [[National Advisory Committee for Aeronautics]] (NACA) forof a [[Hypersonic speed|hypersonic]] research aircraft.{{sfn|Käsmann|1999|p=105}} The [[Request for proposal|requests for proposal]] (RFPs) were published on 30{{spaces}}December 1954 for the airframe and on 4{{spaces}}February 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 [[List of X-planeplanes|X-series]] aircraft, the X-15 was designed to be carried aloft and [[drop test|drop launched]] from under the wing of a [[Boeing B-52 Stratofortress|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 {{convert|8.5|mi|km}} (45,000 feet) and a speed of about {{convert|805|km/h|mph|order=flip|sp=us}}.<ref name="E-4942">{{cite web |url=http://www.dfrc.nasa.gov/Gallery/Photo/X-15/HTML/E-4942.html |title=X-15 launch from B-52 mothership |publisher=Armstrong Flight Research Center |date=6 February 2002 |id=Photo E-4942}}</ref> The X-15 fuselage was long and cylindrical, with rear [[Aircraft fairing|fairings]] that flattened its appearance, and thick, dorsal and ventral wedge-fin stabilizers. Parts of the fuselage (the outer skin<ref name=NASA-FS>{{Cite web|url=http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-052-DFRC.html|title=NASA Dryden Fact Sheets - X-15 Hypersonic Research Program|first=Yvonne|last=Gibbs|date=13 August 2015|website=NASA}}</ref>) were heat-resistant [[nickel]] [[alloy]] ([[Inconel]]-X{{spaces}}750).{{sfn|Käsmann|1999|p=105}} 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.

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.

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 [[Spacecraft attitude control|attitude control]].<ref name=paul2 /> The Reaction Control System (RCS) could be operated in two modes&nbsp;– 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>{{cite book |url=http://www.nasa.gov/centers/dryden/pdf/87709main_H-364.pdf |title=Operational Experience With the X-15 Reaction Control and Reaction Augmentation Systems |publisher=NASA |first1=Calvin R. |last1=Jarvis |first2=Wilton P. |last2=Lock |year=1965 |id=TN D-2864 |oclc=703664750 |access-date=1 October 2011 |archive-date=4 December 2011 |archive-url=https://web.archive.org/web/20111204191553/http://www.nasa.gov/centers/dryden/pdf/87709main_H-364.pdf |url-status=dead }}</ref> The RAS was typically used for approximately three minutes of an X-15 flight before automatic power off.<ref name=jarvis />

The X-15 had an ejection seat designed to operate at speeds up to {{convert|4|Mach|altitude_ft=120000}} and/or {{convert|120000|ft|km}} (23 miles) altitude, although it was never used during the program.<ref name=paul2>{{cite web |url=http://www.sierrafoot.org/x-15/pirep2.html |title=X-15 Pilot Report, Part 2: X-15 Cockpit Check |work=SierraFoot.org |first=Paul |last=Raveling |access-date=1 October 2011}}</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 {{convert|35000|ft|km}} altitude, the cockpit was pressurized to {{convert|3.5|psi|kPa atm|abbr=on}} with nitrogen gas, while oxygen for breathing was fed separately to the pilot.<ref name=paul2 />

By November 1960, Reaction Motors delivered the [[Reaction Motors XLR99|XLR99]] rocket engine, generating {{convert|57000|lb-f|kN}} of thrust. The remaining 175{{spaces}}flights of the X-15 used XLR99 engines, in a single engine configuration. The XLR99 used [[ammonia|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 {{convert|15000|lb|kg|0}} of propellant in 80{{spaces}}seconds;<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">{{cite magazine |url=https://archive.org/stream/Galaxy_v20n01_1961-10#page/n173/mode/2up |title=Galaxy's 5-Star Shelf |magazine=[[Galaxy Science Fiction|Galaxy Magazine]] |first=Floyd C. |last=Gale |volume=20 |issue=1 |page=174 |date=October 1961}}</ref>

On 15{{spaces}}November 1967, U.S. Air Force test pilot Major [[Michael J. Adams]] was killed during [[X-15 Flight 3-65-97|X-15 Flight 191]] when X-15-3, {{nowrap|AF Ser. No. 56-6672}}, 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 {{convert|15|g0|lk=on|abbr=on}} vertical and {{convert|8.0|g0|lk=on|abbr=on}} lateral. The airframe broke apart at {{convert|60000|ft|km}} altitude, scattering the X-15's wreckage across {{convert|50|sqmi|km2}}. On 8{{spaces}}May 2004, a monument was erected at the cockpit's locale, near [[Johannesburg, California]].<ref name="xpress2004">{{cite journal |url=http://www.nasa.gov/centers/dryden/news/X-Press/stories/2004/073004/ppl_adams.html |title=Michael Adams: Remembering a Fallen Hero |journal=The X-Press |first=Peter W. |last=Merlin |volume=46 |issue=6 |date=30 July 2004}}</ref> Major Adams was posthumously awarded Air Force astronaut wings for his final flight in X-15-3, which had reached an altitude of {{convert|81.1|km|mi|order=flip|sp=us}}. In 1991, his name was added to the [[Space Mirror Memorial|Astronaut Memorial]].<ref name="xpress2004" />

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==CurrentAircraft staticon displaysdisplay==

[[File:NASMX-SI-2008-556015 at the Mary Baker Engen Restoration Hangar.jpg|thumb|X-15-1 at56-6670 in the NationalMary AirBaker andEngen SpaceRestoration Museum in Washington, D.CHangar.]]

During 13 of the 199 total X-15 flights, eight pilots flew above {{convert|264,000|ft|mi km}}, thereby qualifying as astronauts according to the [[US Armed Forces]] definition of the [[karman line|space border]]. All five Air Force pilots flew above 50{{spaces}}miles and were awarded military [[astronaut wings]] contemporaneously with their achievements, including Adams, who received the distinction posthumously following the flight{{spaces}}191 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>{{cite web |url=https://www.nasa.gov/missions/research/X-15_wings.html |title=X-15 Pioneers Honored as Astronauts |last=Johnsen |first=Frederick A. |date=23 August 2005 |website=NASA |access-date=16 January 2019 |archive-date=21 September 2022 |archive-url=https://web.archive.org/web/20220921193231/https://www.nasa.gov/missions/research/X-15_wings.html |url-status=dead }}</ref><ref>{{cite web |url=https://www.space.com/1465-nasa-15-pilots-awarded-astronaut-wings.html |title=Former NASA X-15 Pilots Awarded Astronaut Wings |last=Pearlman |first=Robert Z. |date=23 August 2005 |website=space.com}}</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.

| 1960<ref>{{cite web |last1=Conner |first1=Monroe |title=Joseph A. Walker |url=https://www.nasa.gov/centers/armstrong/about/biographies/pilots/joseph-walker.html |website=NASA |access-date=10 September 2023 |date=23 June 2020 |archive-date=6 December 2021 |archive-url=https://web.archive.org/web/20211206050527/https://www.nasa.gov/centers/armstrong/about/biographies/pilots/joseph-walker.html |url-status=dead }}</ref>

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|spanlength ftnote=22{{efn|

|heightspan ftnote=13{{efn|

*13’ 1”22’ 4” Standard aircraft

|empty weight lb=14600{{efn|

*Landing WeightBurn-out weight: 1314,800500 lbslb Standard aircraft

* {{cite book |url=https://history.nasa.gov/monograph31.pdf |title=American X-Vehicles: An Inventory – X-1 to X-50 |series=Monographs in Aerospace History No. 31 |publisher=NASA |first1=Dennis R. |last1=Jenkins |first2=Tony |last2=Landis |first3=Jay |last3=Miller |date=June 2003 |id=SP-2003-4531 |oclc=68623213 |archive-url=https://web.archive.org/web/20200425225303/https://history.nasa.gov/monograph31.pdf |archive-date=25 April 2020 }}