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The North American XF-108 Rapier was a proposed long-range, high-speed
interceptor aircraft An interceptor aircraft, or simply interceptor, is a type of fighter aircraft designed specifically for the defensive interception role against an attacking enemy aircraft, particularly bombers and reconnaissance aircraft. Aircraft that are cap ...
designed by
North American Aviation North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F ...
intended to defend the United States from supersonic
Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
strategic bomber A strategic bomber is a medium- to long-range penetration bomber aircraft designed to drop large amounts of air-to-ground weaponry onto a distant target for the purposes of debilitating the enemy's capacity to wage war. Unlike tactical bombers, ...
s. The aircraft would have cruised at speeds around with an unrefueled
combat radius Radius of action, combat radius, or combat range in military terms, refers to the maximum distance a ship, aircraft, or vehicle can travel away from its base along a given course with normal load and return without refueling, allowing for all safet ...
over , and was equipped with radar and missiles offering engagement ranges up to against bomber-sized targets. To limit development costs, the program shared engine development with the
North American XB-70 Valkyrie The North American Aviation XB-70 Valkyrie was the prototype version of the planned B-70 nuclear-armed, deep-penetration supersonic strategic bomber for the United States Air Force Strategic Air Command. Designed in the late 1950s by North Ame ...
strategic bomber A strategic bomber is a medium- to long-range penetration bomber aircraft designed to drop large amounts of air-to-ground weaponry onto a distant target for the purposes of debilitating the enemy's capacity to wage war. Unlike tactical bombers, ...
program, and used a number of elements of earlier interceptor projects. The program had progressed only as far as the construction of a single wooden mockup when it was cancelled in 1959, due to a shortage of funds and the Soviets' adoption of
ballistic missile A ballistic missile is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are guided only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles stay within the ...
s as their primary means of nuclear attack. Had it flown, the F-108 would have been the heaviest fighter of its era. Prior to the project's cancellation, U.S. President
Dwight D. Eisenhower Dwight David "Ike" Eisenhower (born David Dwight Eisenhower; ; October 14, 1890 – March 28, 1969) was an American military officer and statesman who served as the 34th president of the United States from 1953 to 1961. During World War II, ...
noted that raising the F-108 interceptor force would have cost the U.S. taxpayer $4 billion (equivalent to $ billion today).


Development


LRI-X

During the early 1950s, the USAF proposed a very high-performance, long-range interceptor. On 20 July 1955, formal development of what became known as the Long-Range Interceptor, Experimental (LRI-X) was approved, planned as an F-102 Delta Dagger/
F-106 Delta Dart The Convair F-106 Delta Dart was the primary all-weather interceptor aircraft of the United States Air Force from the 1960s through to the 1980s. Designed as the so-called "Ultimate Interceptor", it proved to be the last specialist interceptor i ...
replacement. The specification was laid down on 6 October 1955, calling for an interceptor that could fly at at a speed of Mach 1.7 (, with a range of .Jenkins and Landis 2008, p. 199. It was to have a two-man crew and at least two engines. A further consideration was that an integrated
fire-control system A fire-control system (FCS) is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs the same task as a ...
would be fitted, allowing the interception of a bomber at and three targets to be destroyed during a single mission. Of the eight interested companies, contracts for preliminary studies were issued to
North American Aviation North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F ...
, Lockheed and Northrop on 11 October 1955, five days after the specification's release. Of the paper designs, the North American proposal, dubbed "NA-236", seemed the most promising. The NA-236 shared some similarities with the XF-108, although the most obvious differences were the additions of two finlets at the midspan of the horizontal stabilizers, and canards. Political and budgetary difficulties led to the cancellation of the program on 9 May 1956.


WS-202A

After considerable confusion, the program was reinstated on 11 April 1957 with North American awarded a contract for two prototypes. The designation F-108 was issued, also known as "Weapon System 202A" (WS-202A). North American's company designation was "NA-257", although it was basically identical to the NA-236. At the time,
Air Defense Command Aerospace Defense Command was a major command (military formation), command of the United States Air Force, responsible for continental air defense. It was activated in 1968 and disbanded in 1980. Its predecessor, Air Defense Command, was est ...
anticipated an order for 480 aircraft.Jenkins and Landis 2008, p. 200. The resulting design went through considerable evolution, owing to both its cutting-edge technology and continual redefinition of the USAF requirements. Early revisions prominently featured canards, with a span of , and a wing of 53.5° sweep. The aircraft in this configuration would have had a maximum takeoff weight of with a operational ceiling. In addition to the F-108's interceptor role, North American proposed it as a
penetration fighter The term penetration fighter has been used to describe a long-range fighter aircraft designed to penetrate enemy air defences and attack defensive interceptors. The concept is similar to the escort fighter, but differs primarily in that the aircra ...
to aid its own
B-70 Valkyrie The North American Aviation XB-70 Valkyrie was the prototype version of the planned B-70 nuclear-armed, deep-penetration supersonic strategic bomber for the United States Air Force Strategic Air Command. Designed in the late 1950s by Nort ...
supersonic bomber prototype. Commonality between the B-70 bomber and the F-108 included the escape capsule and
General Electric YJ93 The General Electric YJ93 turbojet engine was designed as the powerplant for both the North American XB-70 Valkyrie bomber and the North American XF-108 Rapier interceptor. The YJ93 was a single-shaft axial-flow turbojet with a variable-stator c ...
engines. Another role considered was for the F-108 to be "gap-fillers" for the Distant Early Warning (DEW) system; because of its great speed, the F-108 could have scanned up to per hour.Jenkins and Landis 2008, p. 202. From September 1958, substantial engineering and design changes were implemented; however, SAC had lost interest in the escort fighter concept. To accompany the B-70 all the way to its target and back, the F-108 in its initial concept would have, at best, marginal range.Buttler 2007, p. 107. On 30 December 1958, YF-108A preproduction aircraft on order were reduced from 31 to 20 test aircraft and the first test flight was delayed from February to April 1961. The eventual design, which was built as a full-sized XF-108
mockup In manufacturing and design, a mockup, or mock-up, is a scale or full-size model of a design or device, used for teaching, demonstration, design evaluation, promotion, and other purposes. A mockup may be a ''prototype'' if it provides at leas ...
, was displayed to Air Force officials on 17–20 January 1959. The project was given the name "Rapier" on 15 May 1959, following a contest by the Air Defense Command asking airmen for suggestions.Buttler 2007, p. 108.


Cancellation

Even as the XF-108 program was progressing well, there were signs that would ultimately lead to its eventual cancellation. Unconfirmed Soviet bomber threats, the overwhelming trend toward offensive and defensive nuclear missiles in the late 1950s and early 1960s, as well as rising costs, contributed to the termination of the XF-108. The cancellation was announced on 23 September 1959. North American continued refining the design through 1960 in hopes that the program might be revived. Despite the extra money and time spent on the Rapier, it was not wholly in vain; the
North American A-5 Vigilante The North American A-5 Vigilante was an American carrier-based supersonic bomber designed and built by North American Aviation (NAA) for the United States Navy. Prior to 1962 unification of Navy and Air Force designations, it was designated t ...
supersonic carrier-based nuclear strike bomber developed for the U.S. Navy, which was later modified into a carrier-based reconnaissance aircraft, retained the fuselage/weapon package and systems design of the Rapier. In many ways the Vigilante could be seen as the successful application of the Rapier design principles in a Mach 2 supersonic design.
Hughes Aircraft The Hughes Aircraft Company was a major American aerospace and defense contractor founded on February 14, 1934 by Howard Hughes Howard Robard Hughes Jr. (December 24, 1905 – April 5, 1976) was an American business magnate, record-setting p ...
would continue the development of the advanced fire control system and the GAR-9 missile. Development of the F-108 radar and missiles was continued by the USAF and the system was eventually used in the
Lockheed YF-12 The Lockheed YF-12 was an American Mach 3+ capable, high-altitude interceptor prototype, developed and manufactured by American aerospace company Lockheed Corporation. It was developed during the late 1950s and early 1960s as a potenti ...
program. The final configuration for the rear cockpit in the YF-12A looked similar to that of the F-108 since it incorporated the same displays and controls required for the Hughes
AN/ASG-18 The Hughes AN/ASG-18 Fire Control System was a prototype airborne fire control radar system for the planned North American XF-108 Rapier interceptor aircraft, and the Lockheed YF-12 for the United States Air Force. It was the US's first Pulse-Doppl ...
fire control system.


Design

The initial F-108 configuration featured a very large "cranked"
delta wing A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ). Although long studied, it did not find significant applications until the Jet Age, when it proved suitabl ...
. There were fixed ventral stabilizers on the wings, mounted at mid-span, and a tall all-moving vertical tailfin, supplemented by two ventral stabilizers that extended when the
landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...
retracted. Although some earlier versions of the design had separate tailplanes or forward canards, both were abandoned in the final design. The large fuselage and wing had two and five fuel tanks, respectively, giving an estimated combat radius of some .Buttler 2007, p. 106. Top speed was estimated at , about Mach 3, at . The aircraft was powered by two General Electric J93
turbojet The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and ...
engines, also used in North American's XB-70 Valkyrie bomber, in the fuselage. The F-108 was intended to carry the
Hughes AN/ASG-18 The Hughes AN/ASG-18 Fire Control System was a prototype airborne fire control radar system for the planned North American XF-108 Rapier interceptor aircraft, and the Lockheed YF-12 for the United States Air Force. It was the US's first Pulse-Dopp ...
radar, the U.S.'s first
pulse-Doppler radar A pulse-Doppler radar is a radar system that determines the range to a target using pulse-timing techniques, and uses the Doppler effect of the returned signal to determine the target object's velocity. It combines the features of pulse radars an ...
set. It was to have
look-down/shoot-down A radar system has look-down/shoot-down capability if it can detect, track and guide a weapon to an air target that (as seen by the radar) is silhouetted against the ground. Problem and naming Airborne intercept radar relying exclusively on time ...
capability, but could track only one target at a time. The radar was paired with an infra-red search and tracking (IRST) system on the wing leading edges. The radar was used to guide the Hughes GAR-9 (later redesignated AIM-47)
air-to-air missile The newest and the oldest member of Rafael's Python family of AAM for comparisons, Python-5 (displayed lower-front) and Shafrir-1 (upper-back) An air-to-air missile (AAM) is a missile fired from an aircraft for the purpose of destroying a ...
, three of which would be carried on a rotary launcher in an internal weapons bay. The GAR-9 was a very large, long-range weapon with its own radar set for terminal homing. It was intended to fly at Mach 6, with a range of almost .


XQ-11 target drone

As part of WS-202A, a design for a high-speed (Mach 3+) aerial target for use in testing the F-108's weapons system was proposed. The
Wright Air Development Center The Aeronautical Systems Center (ASC) is an inactivated Air Force product center that designed, developed and delivered weapon systems and capabilities for U.S. Air Force, other U.S. military, allied and coalition-partner warfighters. ASC managed ...
requested the designation XQ-11 for the target design; the request was denied due to the early stage of development, and the F-108 program was cancelled before further work was undertaken.


Specifications (XF-108)


See also


References


Notes


Citations


Bibliography

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External links


Anigrand Models produces 1/72 and 1/144 scale resin kits of the XF-108




* ttp://www.alternatewars.com/SAC/F-108_Rapier_SAC_-_2_May_1958.pdf US Standard Aircraft Characteristics Document for F-108's early iteration
US Standard Aircraft Characteristics Document for F-108's pre-mock-up iteration
{{USAF system codes Cancelled military aircraft projects of the United States Tailless delta-wing aircraft F-108 Rapier Twinjets