Editing Sound barrier (section)

===Breaking the sound barrier===
[[File:MilesM52 1.jpg|thumb|right|The prototype [[Miles M.52]] turbojet powered aircraft, designed to achieve supersonic level flight]]
In 1942, the [[United Kingdom]]'s [[Ministry of Aviation]] began a top-secret project with [[Miles Aircraft]] to develop the world's first aircraft capable of breaking the sound barrier. The project resulted in the development of the prototype [[Miles M.52]] turbojet-powered aircraft, which was designed to reach 1,000&nbsp;mph (417&nbsp;m/s; 1,600&nbsp;km/h) (over twice the existing speed record) in level flight, and to climb to an altitude of 36,000&nbsp;ft (11&nbsp;km) in 1&nbsp;minute 30&nbsp;seconds.

A number of advanced features were incorporated into the resulting M.52 design, which resulted from consulting experts in government establishments with a current knowledge of [[supersonic]] [[aerodynamics]]. In particular, the design featured a conical nose, for low supersonic drag,<ref>https://www.researchgate.net/publication/288803814_On_the_aerodynamics_of_the_Miles_M52_E2443_-_A_historical_perspective p.137</ref> and sharp wing leading edges. The design used very thin wings of biconvex section proposed by [[Jakob Ackeret]] for [[wave drag|low drag]]. The wing tips were "clipped" to keep them clear of the [[Cone (geometry)|conical]] [[shock wave]] generated by the nose of the aircraft. The fuselage had a 5-foot diameter with an annular fuel tank around the engine.<ref>"Project Cancelled-The Disaster of Britain's Abandoned Aircraft Projects", Wood,{{ISBN|1 85488 026 8}}, 1990, p. 20</ref>

[[Image:M52 model.jpg|thumb|left|One of the Vickers models undergoing supersonic wind-tunnel testing at the [[Royal Aircraft Establishment]] (RAE) around 1946]]
Another critical addition was the use of a power-operated [[stabilator]], also known as the ''all-moving tail'', ''flying tail'', or ''all-flying tail'', a key to transonic and supersonic flight control, which contrasted with traditional hinged [[tailplane]]s (horizontal stabilizers) connected mechanically to the pilots [[control column]]. Conventional control surfaces became ineffective at the high subsonic speeds then being achieved by fighters in dives, due to the aerodynamic forces caused by the formation of shockwaves at the hinge and the rearward movement of the [[Center of pressure (fluid mechanics)|centre of pressure]], which together could override the control forces that could be applied mechanically by the pilot, hindering recovery from the dive.<ref name="Brown 1970">Brown, Eric (August–November 1980). "Miles M.52: The Supersonic Dream". ''Air Enthusiast Thirteen''. {{ISSN|0143-5450}}.</ref><ref>[[Roland Beamont|Beamont, Roland]]. ''Testing Early Jets''. London: Airlife, 1990. {{ISBN|1-85310-158-3}}.</ref> A major impediment to early transonic flight was [[control reversal]], the phenomenon which caused flight inputs (stick, rudder) to switch direction at high speed; it was the cause of many accidents and near-accidents. A stabilator is required for an aircraft to pass through the transonic speed range safely, without losing pilot control. The Miles M.52 was the first instance of this solution, which has since been universally applied.

Initially, the aircraft was to use [[Frank Whittle]]'s latest engine, the [[Power Jets W.2#Variants|Power Jets W.2/700]], with which it would only reach supersonic speed in a shallow dive. To develop a fully supersonic version of the aircraft, extra thrust would be provided with the addition of the No.4 augmentor which gave extra airflow from a ducted fan and reheat behind the fan.<ref>{{cite journal |url=http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%201965.html |title=Miles on Supersonic Flight |journal=Aviation History |date=3 October 1946 |page=355 |access-date=23 November 2013 |archive-date=5 September 2018 |archive-url=https://web.archive.org/web/20180905175732/https://www.flightglobal.com/pdfarchive/view/1946/1946%20-%201965.html |url-status=live }}</ref>

Although the project was eventually cancelled, the research was used to construct an uncrewed 30% scale model of the M.52 that went on to achieve a speed of [[Mach number|Mach]] 1.38 in a successful, controlled [[transonic]] and [[supersonic]] level test flight in October 1948; this was a unique achievement at that time which provided "some validation of the aerodynamics of the M.52 upon which the model was based".<ref>{{cite journal | url=https://doi.org/10.1017/S0001924000003602 | doi=10.1017/S0001924000003602 | title=On the aerodynamics of the Miles M.52 (E.24/43) – a historical perspective | date=2010 | last1=Brinkworth | first1=B. J. | journal=The Aeronautical Journal | volume=114 | issue=1153 |page=154 | url-access=subscription }}</ref>

Meanwhile, test pilots achieved high speeds in the [[Tailless aircraft|tailless]], [[swept-wing]] [[de Havilland DH 108]]. One of them was [[Geoffrey de Havilland, Jr.]], who was killed on 27 September 1946 when his DH 108 broke up at about Mach 0.9.<ref>Watkins, David (1996), ''de Havilland Vampire: The Complete History'', Thrupp, Gloucestershire: Budding Books, p. 40, {{ISBN|1-84015-023-8}}.</ref> [[John Derry]] has been called "Britain's first supersonic pilot"<ref>Rivas, Brian, and Bullen, Annie (1996), ''John Derry: The Story of Britain's First Supersonic Pilot'', William Kimber, {{ISBN|0-7183-0099-8}}.</ref> because of a dive he made in a DH 108 on 6 September 1948.