Editing Convair F-102 Delta Dagger (section)

==Design and development==

===Background===
[[File:Convair YF-102 53-1785 on Ramp E-2550.jpg|thumb|upright|The YF-102 with its original fuselage]]

On 8 October 1948, the board of senior officers of the [[United States Air Force]] (USAF) issued recommendations that the service organize a competition for a new interceptor scheduled to enter service in 1954; as such, the all-new design would initially be dubbed the "1954 Ultimate Interceptor".<ref>Donald 1997, p. 207.</ref> Four months later, on 4 February 1949, the USAF approved the recommendation and prepared to hold a corresponding competition during the following year.<ref name = "Becker p.68">Becker 2012, p. 68.</ref> In November 1949, the USAF decided that the new aircraft would be built around a [[fire-control system]] (FCS). The FCS was to be designed before the airframe to ensure compatibility.<ref name="Donald p.68-9">Donald 2003, pp. 68–69.</ref><ref name = "Becker p.689">Becker 2012, pp. 68-69.</ref> The airframe and FCS together were called the weapon system.

In January 1950, the USAF's [[Air Force Logistics Command|Air Materiel Command]] issued [[request for proposal]]s (RFPs) to 50 companies for the FCS, of which 18 responded. By May, the list was revised downward to 10. Meanwhile, a board at the U.S. Department of Defense headed by [[Major General]] [[Gordon P. Saville]] reviewed the proposals, and distributed some to the [[Chief Scientist of the U.S. Air Force|George E. Valley]]-led Air Defense Engineering Committee. Following recommendations by the committee to the Saville Board, the proposals were further reduced to two competitors, [[Hughes Aircraft]] and [[North American Aviation]]. Although the Valley Committee thought it was best to award the contract to both companies, Hughes was chosen by Saville and his team on 2 October 1950.<ref name="Donald p.69">Donald 2003, pp. 69, 228.</ref><ref name = "Becker p.69">Becker 2012, p. 69.</ref>

In June 1950, the requirement for the airframe was formally issued; during January 1951, six aircraft manufacturers submitted nine responses.<ref name = "Becker p.69"/> On 2 July 1954, three of the responding companies, Convair, [[Republic Aviation|Republic]], and [[Lockheed Corporation|Lockheed]], were authorised to proceed with the building of a mockup. Upon completion, the three designs would be competitively reviewed, the best of which would lead to the awarding of a single production contract under the name ''Project MX-1554''. Prior to this requirement, Convair had performed considerable early research into delta-winged aircraft and had experimented with various different designs, two of which fell under the name ''P-92''.<ref name = "Becker p.6668">Becker 2012, pp. 66-68.</ref> For the era, Convair's submitted design was relatively unorthodox, not only in terms of the delta wing configuration but the decision to carry all munitions within an internal weapons bay to reduce [[Drag (physics)#Aerodynamics|drag]]; despite this, Republic's design was even more radical, proposing to use [[ramjet]] propulsion to attain speeds in excess of Mach 3.<ref name = "Becker p.69"/>

===Selection===
Ultimately, Convair's design emerged as the front runner for the requirement, which was officially designated ''XF-102''. Lockheed had chosen to drop out to concentrate on other opportunities while Republic's design had been judged to involve too much technical risk to meet the 1954 deadline for service entry, thus was disqualified, making Convair the de facto winner.<ref name="Donald p.69"/><ref name="Becker p.6970">Becker 2012, pp. 69-70.</ref> The development of three different designs has been considered to be too expensive to proceed with, thus only Convair was permitted to do so in November 1951.<ref name = "Becker p.72">Becker 2012, p. 72.</ref> From an early stage, USAF officials had decided to use the Cook-Craigie Plan for the aircraft's manufacturing; under this concept, production tooling and facilities would be created while a small pre-production batch of aircraft would be completed, the aim being to eliminate the need for a lengthy prototype program, instead incorporating any changes required into the production line. However, if substantial modifications were necessary, re-tooling would then become necessary as well.<ref name = "Becker p.71">Becker 2012, p. 71.</ref> In December 1951, in order to accelerate the aircraft's development, it was proposed to equip the prototypes and pre-production aircraft with the less-powerful [[Westinghouse J40]] [[turbojet]].<ref name = "Becker p.70">Becker 2012, p. 70.</ref>

During early 1953, by which point construction of the first aircraft had reached an advanced stage, it had become clear that there were serious design challenges present, including [[wind tunnel]] testing that revealed early performance projections to have been overly optimistic.<ref name = "Becker p.7172">Becker 2012, pp. 71-72.</ref> Furthermore, there had been sustained delays to both the [[Curtiss-Wright J67]] engine, a licensed derivative of the [[Rolls-Royce Olympus|Bristol-Siddeley Olympus]] which was still in development,<ref name="Knaack p159-160">Knaack 1978, pp. 159–160.</ref> and the MA-1 (formerly ''MX-1179'') FCS;<ref name="Wegg p200">Wegg 2000, p. 200.</ref> to address the latter, decision makers opted to order an interim aircraft with the J40 and a simpler FCS (initially referred to as ''E-9'') into production as the ''F-102A''.<ref name = "Becker p.7071"/> The failure of the J40 led to the [[Pratt & Whitney J57]] turbojet with afterburner, rated with {{Convert|10000|lbf|kN}} of thrust,<ref name="Donald p.70">Donald 2003, p. 70.</ref> being substituted for the prototypes and F-102As.<ref name="Wegg p200-1">Wegg 2000, pp. 200–201.</ref><ref name="Knaack p160-1">Knaack 1978, pp. 160–161.</ref> This aircraft was intended to be temporary, pending the development of the more advanced F-102B, which would employ the more advanced J67. The F-102B would later evolve to become the F-106A, dubbed the "Ultimate Interceptor".<ref name="Donald p.70"/><ref name="Becker p.7071">Becker 2012, pp. 70-71.</ref>

On 23 October 1953, the ''YF-102'' prototype conducted its first flight from [[Edwards Air Force Base]], piloted by Convair's chief test pilot Richard L. Johnson.<ref name = "Becker p.7273">Becker 2012, pp. 72-73.</ref> Its flying career was very brief as it was lost in an accident only nine days later during a failed attempt to reach Mach 1. The accident, which was caused by severe buffeting, seriously injured Johnson.<ref name = "Becker p.73">Becker 2012, p. 73.</ref> The second aircraft flew on 11 January 1954, confirming a dismal performance. [[Transonic]] [[Drag (aerodynamics)#Drag in aerodynamics|drag]] was much higher than expected, and the aircraft was limited to Mach&nbsp;0.98 (i.e. subsonic), with a ceiling of 48,000&nbsp;ft (14,630&nbsp;m), far below the requirements.<ref name="Knaack p163-4">Knaack 1978, pp. 163–164.</ref>

===Major redesign===
[[File:Convair YF-102A on ramp E-2551.jpg|thumb|upright|YF-102A with pinched "area rule" fuselage, narrower canopy and redesigned intakes]]

During mid 1953, Convair concluded that it needed to take action to address the F-102's shortcomings to prevent its cancellation, and promptly embarked on a major redesign effort.<ref name = "Becker p.7273"/> It was decided to incorporate the recently discovered [[Whitcomb area rule|area rule]], the application of which simultaneously simplified both production and maintenance of the aircraft.<ref>{{cite web |last1 = Baals |first1 = Donald D. |title = WIND TUNNELS OF NASA. Chapter 5 - The Era of High-Speed Flight. The Area Rule and the F-102 Story |url = https://history.nasa.gov/SP-440/ch5-10.htm |website = history.nasa.gov |publisher = US Library of Congress, Supt. of Docs. no.: NAS 1.21:440 |access-date = 16 July 2014 |url-status = live |archive-url = https://web.archive.org/web/20130607031028/http://history.nasa.gov/SP-440/ch5-10.htm |archive-date = 7 June 2013}}</ref> This redesign entailed the lengthening of the fuselage by 11&nbsp;ft (3.35&nbsp;m), being "pinched" at the midsection (dubbed the "[[Coke bottle#Contour bottle design|Coke Bottle]] configuration"), with two large fairings on either side of the engine nozzle, with revised intakes and a new, narrower canopy. A more powerful model of the J57 was installed while the aircraft structure was also lightened.<ref name="Gunston F102 p513-4">Gunston 1957, pp. 513–514.</ref><ref name="Wegg p201">Wegg 2000, p. 201.</ref>

In parallel to this effort, the wing was also redesigned to be both thinner and wider. The [[leading edge]] was reprofiled with a conical droop, with the apex at the root, as to improve handling at low speeds. Because the droop remained within the shock cone of the leading edge, the drag rise at supersonic speeds was minimal. A second, inboard fence was also added at the time.<ref>Mendenhall 1983, p. 27.</ref><ref>Jones, Lloyd S. ''U.S. Fighters'', Aero, 1975. pp. 272-274.</ref> A new canopy was also adopted while the tail was shifted slightly aft. The level of changes that could be implemented were restrained by the redesign having occurred at such an advanced stage of development.<ref name = "Becker p.74">Becker 2012, p. 74.</ref> Yet, the overall changes made were so substantial that two-thirds of the roughly 30,000 tools created to manufacture the YF-102 were scrapped or modified before quantity production had even commenced.<ref name = "Becker p.73"/>

On 20 December 1954, the first revised aircraft, designated ''YF-102A'', made its first flight only 118 days after work on the redesign had started.<ref name = "Becker p.74"/> The next day, it exceeded Mach&nbsp;1 for the first time.<ref name="Wegg p201"/><ref name = "Becker p.7475">Becker 2012, pp. 74-75.</ref> The revised design quickly demonstrated that it could attain a speed of Mach&nbsp;1.22 and a ceiling of 53,000&nbsp;ft (16,154&nbsp;m). These performance improvements were sufficient for the USAF to agree to procure the F-102; accordingly, a new production contract was signed during March 1954.<ref name="Knaack p166">Knaack 1978, p. 166.</ref> On 24 June 1955, the first flight of a production standard F-102 occurred.<ref name = "Becker p.75">Becker 2012, p. 75.</ref> From the 26th production aircraft onwards, a taller vertical tail with a 40 percent greater surface area was fitted to counteract flutter and a lack of directional control at high speeds; existing aircraft were also retrofitted with this change.<ref name = "Becker p.76">Becker 2012, p. 76.</ref>

===Further development===
[[File:Convair TF-102A Delta Dagger on lakebed.png|thumb|upright|left|A TF-102A, illustrating the widened cockpit]]

The production F-102A had the Hughes MC-3 FCS, which was later upgraded in service to the MG-10; it was used to locate enemy targets, steer interception courses, and control weapons deployment.<ref name = "Becker p.77">Becker 2012, p. 77.</ref> The F-102 was the first USAF fighter to be designed without a gun, instead relying on missiles as its primary armament.<ref name = "Becker p.76"/> It had a three-segment internal weapons bay under the fuselage for [[air-to-air missile]]s. Initial armament was three pairs of [[AIM-4 Falcon|GAR-1/2/3/4]] (''Later re-designated as AIM-4'') Falcon missiles, which included both [[infrared homing]] and [[semi-active radar homing]] variants. The doors of the two forward bays each had tubes for 12 [[Folding-Fin Aerial Rocket]]s (for a total of 24 "FFAR", with initially 2&nbsp;in (51&nbsp;mm) being fitted and later 2.75&nbsp;in (70&nbsp;mm) replacing them.<ref name = "Becker p.7677">Becker 2012, pp. 76-77.</ref> The F-102 was later upgraded to allow the carrying of up to two [[AIM-26 Falcon|GAR-11/AIM-26]] Nuclear Falcon missiles in the center bay.<ref name = "Becker p.8485">Becker 2012, pp. 84-85.</ref> The larger size of this weapon required redesigned center bay doors with no rocket tubes. Plans were considered to fit the [[AIR-2|MB-1 Genie]] nuclear rocket to the design, but although a Genie was test fired from a YF-102A in May 1956, it was never adopted.<ref name="Pea p34"/><ref name = "Becker p.85">Becker 2012, p. 85.</ref>

[[File:Convair F-102A MC-3 fire control system mock-up 060922-F-1234S-038.jpg|thumb|Hughes MC-3 fire control system and radar antenna]]
The F-102 received several major modifications during its operational lifetime, with most airframes being retrofitted with [[infra-red search and track]]ing systems, [[radar warning receiver]]s, transponders, backup [[artificial horizon]]s, and improvements to the [[fire control system]].<ref name="Taylor">"Taylor 1995, pp. 92–93.</ref><ref name = "Becker p.7879">Becker 2012, pp. 78-79.</ref> A proposed close-support version (never built) would have incorporated an internal [[Gatling gun]], and an extra two [[hardpoint]]s for bombs, supplementing the two underwing pylons all production F-102s were fitted with for [[drop tank]]s (the use of which reduced the craft to subsonic performance<ref>{{cite web|last1=Baugher|first1=Joseph F.|title=Convair F-102A Delta Dagger|url=http://www.joebaugher.com/usaf_fighters/f102_1.html|website=JoeBaugher.com|publisher=Joseph F. Baugher|access-date=8 February 2022|url-status=live|archive-url=https://web.archive.org/web/20101105182346/http://joebaugher.com/usaf_fighters/f102_1.html |archive-date=2010-11-05 }}</ref>).  To alleviate this, bigger internal fuel tanks and an [[in-flight-refueling]] probe were fitted.<ref name="Taylor"/> 

In response to a USAF request for a specialized twin-seat trainer, Convair begun development of the TF-102A in April 1952.<ref name = "Becker p.79">Becker 2012, p. 79.</ref> The side-by-side seating design, popularized in the 1950s (and used with the American [[Cessna T-37]], British [[Hawker Hunter]] T.7 and [[English Electric Lightning]] T.4, among others), would require a redesign of the cockpit and a nose almost as wide as that of a Convair 340 commercial airliner. Development was put on hold despite being authorized on 16 April 1953 until issues with the fighter model were sufficiently addressed; the first firm order for the TF-102A was issued in July 1954, and a maiden flight made on 8 November 1955.<ref name = "Becker p.7980">Becker 2012, pp. 79-80.</ref> The new nose introduced buffeting, the source of which was traced to the bulbous canopy. Vortex generators were added to the top of the canopy to prevent the buffet which had started at about Mach 0.72.<ref name = "Schmidt p.95">Schmidt 1997, p. 95.</ref><ref name = "Becker p.81">Becker 2012, p. 81.</ref> The intake ducts were revised as the inlets were repositioned. Despite the many changes, the aircraft was combat-capable, although this variant was predictably slower, reaching only subsonic speeds in level flight.<ref>Gunston 1981, p. 26.</ref> A total of 111 TF-102As were eventually manufactured.<ref name = "Becker p.8182">Becker 2012, pp. 81-82.</ref> 

The numerous inherent design and technical limitations of the F-102 led to a proposed successor, initially known as the F-102B "Ultimate Interceptor". The improved design, in which the proposed Curtiss-Wright J67 jet engine was eventually replaced by a [[Pratt & Whitney J75]], underwent so many aerodynamic changes (including variable-geometry inlets) that it essentially became an entirely new aircraft and hence was redesignated and produced as the F-106 Delta Dart. Convair would also use a delta wing design in the Mach&nbsp;2 class [[Convair B-58 Hustler]] bomber.