XF-108 Rapier
Encyclopedia
The North American XF-108 Rapier was a proposed long-range, high-speed interceptor aircraft
designed by North American Aviation
. Initiated to defend the United States from supersonic Soviet bombers, the program, initially called NA-257, was cancelled in 1959 due to a shortage of funds and the Soviet adoption of ballistic missile
s as their primary means of nuclear attack. Only one mock-up was constructed. Had it flown, it would have been the heaviest fighter of its era, surpassing the Soviet Tupolev Tu-128.
In the early 1950s, the United States Air Force
(USAF) began formulating specifications for an F-102/F-106 replacement. The original requirements called for an aircraft with a top speed of Mach 1.7. A number of companies submitted their proposals, with the winner being North American's XF-108. Revised specifications saw the aircraft's top speed increased to Mach 3, powered by the GE J93 turbojet. Following the program's termination, the fire-control system
, incorporating the Hughes GAR-9
missile, was adapted for the Lockheed A-12.
1.7 (1122 mph (1,805.7 km/h), with a range of 1000 miles (1,609.3 km). It was to have a two-man crew and at least two engines. A further consideration was that an integrated fire-control system
would be fitted, allowing interception of a bomber at 60 nmi (111.1 km) 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
, 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. 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". North American's company designation was "NA-257", although it was basically identical to the NA-236. At the time, Air Defense Command anticipated an order for 480 aircraft.
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 19 ft 10 in (6.04 m), and a wing of 53.5° sweep. The aircraft in this configuration would have a maximum take-off weight of 99,400 lb (45,088 kg) with a 72,550-feet (22,113 m) operational ceiling. In addition to the F-108's interceptor role, North American proposed it as an escort fighter
for its own B-70 Valkyrie supersonic bomber prototype. Commonality between the B-70 bomber and the F-108 included the escape capsule and General Electric YJ93
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 278000 square miles (720,016.7 km²) per hour.
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. On 30 December 1958, YF-108A pre-production 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 mock-up, 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.
Hughes Aircraft
would continue 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
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 ASG-18 fire control system.
The initial F-108 configuration featured a very large "cranked" delta wing
. 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
retracted. Although some earlier versions of the design had had separate tailplanes and later forward canards
, both were abandoned in the final design. The large fuselage and wing have two and five fuel tanks, respectively, giving an estimated combat radius of some 1100 nautical miles (2,037.2 km). Top speed was estimated at 1980 miles per hour (3,186.5 km/h), about Mach 3, at 81800 feet (24,932.6 m). The aircraft was powered by two General Electric J93 turbojet 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
radar, the U.S.'s first pulse-Doppler radar
set. It was to have look-down/shoot-down
capability, but could only track 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
, 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 112 miles (180.2 km).
Interceptor aircraft
An interceptor aircraft is a type of fighter aircraft designed specifically to prevent missions of enemy aircraft, particularly bombers and reconnaissance aircraft. Interceptors generally rely on high speed and powerful armament in order to complete their mission as quickly as possible and set up...
designed by North American Aviation
North American Aviation
North American Aviation was a major US aerospace manufacturer, responsible for a number of historic aircraft, including the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F-86 Sabre jet fighter, the X-15 rocket plane, and the XB-70, as well as Apollo Command and Service...
. Initiated to defend the United States from supersonic Soviet bombers, the program, initially called NA-257, was cancelled in 1959 due to a shortage of funds and the Soviet adoption of ballistic missile
Ballistic missile
A ballistic missile is a missile that follows a sub-orbital ballistic flightpath with the objective of delivering one or more warheads to a predetermined target. The missile is only guided during the relatively brief initial powered phase of flight and its course is subsequently governed by the...
s as their primary means of nuclear attack. Only one mock-up was constructed. Had it flown, it would have been the heaviest fighter of its era, surpassing the Soviet Tupolev Tu-128.
In the early 1950s, the United States Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
(USAF) began formulating specifications for an F-102/F-106 replacement. The original requirements called for an aircraft with a top speed of Mach 1.7. A number of companies submitted their proposals, with the winner being North American's XF-108. Revised specifications saw the aircraft's top speed increased to Mach 3, powered by the GE J93 turbojet. Following the program's termination, the fire-control system
Fire-control system
A fire-control system is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a weapon system in hitting its target. It performs the same task as a human gunner firing a weapon, but attempts to do so faster and more...
, incorporating the Hughes GAR-9
AIM-47 Falcon
The Hughes AIM-47 Falcon, originally GAR-9, was a very long-range high-performance air-to-air missile that shared the basic design of the earlier AIM-4 Falcon. It was developed in 1958 along with the new Hughes AN/ASG-18 radar fire-control system intended to arm the Mach 3 XF-108 Rapier interceptor...
missile, was adapted for the Lockheed A-12.
Development
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 a F-102 Delta Dagger/F-106 Delta Dart replacement. The specification was laid down on 6 October 1955, calling for an interceptor that could fly at 60000 ft (18,288 m) at a speed of MachMach number
Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...
1.7 (1122 mph (1,805.7 km/h), with a range of 1000 miles (1,609.3 km). It was to have a two-man crew and at least two engines. A further consideration was that an integrated fire-control system
Fire-control system
A fire-control system is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a weapon system in hitting its target. It performs the same task as a human gunner firing a weapon, but attempts to do so faster and more...
would be fitted, allowing interception of a bomber at 60 nmi (111.1 km) 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
North American Aviation was a major US aerospace manufacturer, responsible for a number of historic aircraft, including the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F-86 Sabre jet fighter, the X-15 rocket plane, and the XB-70, as well as Apollo Command and Service...
, Lockheed
Lockheed Corporation
The Lockheed Corporation was an American aerospace company. Lockheed was founded in 1912 and later merged with Martin Marietta to form Lockheed Martin in 1995.-Origins:...
and Northrop
Northrop Corporation
Northrop Corporation was a leading United States aircraft manufacturer from its formation in 1939 until its merger with Grumman to form Northrop Grumman in 1994. The company is known for its development of the flying wing design, although only a few of these have entered service.-History:Jack...
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. 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". North American's company designation was "NA-257", although it was basically identical to the NA-236. At the time, Air Defense Command anticipated an order for 480 aircraft.
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 19 ft 10 in (6.04 m), and a wing of 53.5° sweep. The aircraft in this configuration would have a maximum take-off weight of 99,400 lb (45,088 kg) with a 72,550-feet (22,113 m) operational ceiling. In addition to the F-108's interceptor role, North American proposed it as an escort fighter
Escort fighter
The escort fighter was a World War II concept for a fighter aircraft designed to escort bombers to and from their targets.The perfect escort fighter had long range, a lengthy combat loiter time to protect the bombers, and enough internal fuel to return home...
for its own B-70 Valkyrie supersonic bomber prototype. Commonality between the B-70 bomber and the F-108 included the escape capsule and General Electric YJ93
General Electric YJ93
-See also:-External links:...
engines. Another role considered was for the F-108 to be "gap-fillers" for the Distant Early Warning
Distant Early Warning Line
The Distant Early Warning Line, also known as the DEW Line or Early Warning Line, was a system of radar stations in the far northern Arctic region of Canada, with additional stations along the North Coast and Aleutian Islands of Alaska, in addition to the Faroe Islands, Greenland, and Iceland...
(DEW) system; because of its great speed, the F-108 could have scanned up to 278000 square miles (720,016.7 km²) per hour.
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. On 30 December 1958, YF-108A pre-production 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 mock-up, 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.
Cancellation
Even as the XF-108 program was progressing well, there were signs which 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. 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 supersonic reconnaissance bomber developed for the U.S. Navy 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
Hughes Aircraft
Hughes Aircraft Company was a major American aerospace and defense contractor founded in 1932 by Howard Hughes in Culver City, California as a division of Hughes Tool Company...
would continue 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
Lockheed YF-12
The Lockheed YF-12 was an American prototype interceptor aircraft, which the United States Air Force evaluated as a development of the highly-secret Lockheed A-12 that also spawned the SR-71 Blackbird.-Design and development:...
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 ASG-18 fire control system.
Design
Delta wing
The delta wing is a wing planform in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta .-Delta-shaped stabilizers:...
. 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
Landing Gear is Devin the Dude's fifth studio album. It was released on October 7, 2008. It was his first studio album since signing with the label Razor & Tie. It features a high-profile guest appearance from Snoop Dogg. As of October 30, 2008, the album has sold 18,906 copies.-Track...
retracted. Although some earlier versions of the design had had separate tailplanes and later forward canards
Canard (aeronautics)
In aeronautics, canard is an airframe configuration of fixed-wing aircraft in which the forward surface is smaller than the rearward, the former being known as the "canard", while the latter is the main wing...
, both were abandoned in the final design. The large fuselage and wing have two and five fuel tanks, respectively, giving an estimated combat radius of some 1100 nautical miles (2,037.2 km). Top speed was estimated at 1980 miles per hour (3,186.5 km/h), about Mach 3, at 81800 feet (24,932.6 m). The aircraft was powered by two General Electric J93 turbojet 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
Hughes AN/ASG-18
The Hughes AN/ASG-18 was a prototype fire control system and radar, originally intended for the XF-108 Rapier interceptor aircraft, for the United States Air Force....
radar, the U.S.'s first pulse-Doppler radar
Pulse-doppler radar
Pulse-Doppler is a 4D radar system capable of detecting both target 3D location as well as measuring radial velocity . It uses the Doppler effect to avoid overloading computers and operators as well as to reduce power consumption...
set. It was to have look-down/shoot-down
Look-down/shoot-down
Look-down/shoot-down is a capability a radar system is said to possess if it is able to detect, track and put a weapon onto an air target moving below the horizon as seen by the radar...
capability, but could only track 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
AIM-47 Falcon
The Hughes AIM-47 Falcon, originally GAR-9, was a very long-range high-performance air-to-air missile that shared the basic design of the earlier AIM-4 Falcon. It was developed in 1958 along with the new Hughes AN/ASG-18 radar fire-control system intended to arm the Mach 3 XF-108 Rapier interceptor...
(later redesignated AIM-47) air-to-air missile
Air-to-air missile
An air-to-air missile is a missile fired from an aircraft for the purpose of destroying another aircraft. AAMs are typically powered by one or more rocket motors, usually solid fuelled but sometimes liquid fuelled...
, 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 112 miles (180.2 km).
Specifications (XF-108)