The layout of the fighter XF-108 Rapier
The project of an unusual fighter needed to accompany strategic bombers arose in the United States in the second half of the 1950s. For its time, the novelty stood out with an excellent set of flight performance. If the plane was really built, it would be a breakthrough. However, the XF-108 Rapier fighter did not advance beyond the project. A heavy escort fighter never took to the sky.
The advent of the XF-108 Rapier
The 1950s marked the final transition to jet combat aviation. It was at this time that the United States was close to presenting the world with unique supersonic jet engines with unprecedented performance characteristics. The experimental fighter XF-108 Rapier, which began to be created in the late 1950s, just belonged to similar projects. The new fighter could well change the idea of aviation. Work on its creation was carried out in conjunction with the development of a new strategic supersonic bomber B-70 Valkyrie.
The well-known American company North American, which previously presented the world with one of the best fighters of the Second World War P-51 Mustang, worked on the creation of aircraft. Work on the strategic bomber and escort fighter was carried out as part of a project initiated in 1957 by the US Air Force command to create new strategic systems. The project provided for the creation of a supersonic strategic bomber capable of speeds of up to three Machs, as well as an escort fighter that would not lag behind the bomber in terms of speed. The third area of the project was the creation of intercontinental cruise missiles, which also had supersonic speed.
XB-70A "Valkyrie" in flight
If the US military quickly abandoned cruise missiles in favor of more profitable and promising ICBMs, then work on the bomber and fighter was quite active. Although the XF-108 Rapier never took to the skies, its closest relative, the B-70 Valkyrie strategic bomber, was embodied in metal. The bomber was built in duplicate and first flew in 1964. This fact did not go unnoticed by Soviet intelligence. The USSR’s response to American developments was the creation of the supersonic fighter-interceptor E-155, which in the future turned into a serial MiG-25 fighter.
Supersonic escort fighter and its capabilities
The contract for the construction of two supersonic escort fighters was signed with North American on June 6, 1957. Two new aircraft received the designation XF-108 (designation within the company - NA-257). The new fighter was originally designed as a machine capable of flying over a long range and at a very high speed - about three Machs. The aircraft was planned to be used simultaneously as both a long-range interceptor, which was supposed to intercept the strategic bombers of the USSR in the skies over the Arctic, and as a heavy escort fighter for the American strategic supersonic B-70 Valkyrie bombers. In this regard, the aircraft had to fulfill the same role as the P-51 Mustang, which accompanied the "flying fortresses" during the Second World War.
Despite the fact that the XF-108 Rapier was never built in metal, the project was promising and stood out with a number of interesting innovations. According to the initial plans, the fighter, like the B-70 Valkyrie bomber being created in parallel, was supposed to get two General Electric J95-GE-5 turbojet engines (it was planned to install six such engines on the bomber), working on pentaborane borohydrogen fuel. By its qualities, the pentaborane exceeded the classic aviation kerosene. However, it quickly became clear that the use of new fuel allowed increasing the flight range of aircraft by only 10 percent. At the same time, this fuel remained an extremely toxic and harmful substance. In August 1959, work on the creation of the J95-GE-5 engine was closed along with work on the creation of hydrogen fuel.
The second distinctive feature of the new fighter was to become a fire control system, complex for its time, and a set of used weapons. The SLA of the aircraft was created on the basis of the latest ASG-18 pulse-Doppler radar, which was supposed to provide target selection in the lower hemisphere. Powerful airborne radar equipment was supposed to work in conjunction with the latest GAR-9 Super Falcon guided air-to-air missile. A distinctive feature of the rocket was its extremely high flight speed - about 6 Machs and a long range - 176 km.
The heavy fighter was supposed to carry at once three such missiles weighing 365 kg each, while it was planned to place the missiles in the internal weapons compartment. To aim a new missile at the target, it was planned to use a combined homing head. At a medium distance, a semi-active radar guidance system was used, and an infrared guidance system was used at the end of the flight.
Externally, the XF-108 Rapier was a large aircraft equipped with two turbojet engines. After abandoning the power plant running on hydrogen fuel, the designers returned to the classic General Electric J93-GE-3AR engines with an afterburner thrust of 130,3 kN each. It was believed that this would be enough to disperse an aircraft with a maximum take-off mass of more than 46 tons, to a speed of 3186 km / h.
GAR-9 missile in the internal compartment of the XF-108 fighter
Structurally, the XF-108 was an all-metal aircraft, made according to the "duck" scheme and having a characteristic wing of a triangular shape. The wingspan was 17,5 meters, the wing area - 173,5 square meters. According to the designers, the triangular wing of the fighter was to receive mechanization along the entire trailing edge, as well as the wingtips that deviate downward. The same decision was planned for the Valkyrie strategic bomber. As conceived by engineers at North American, this was to increase the directional stability of the new aircraft, especially when flying at supersonic speeds. The crew of the fighter was to consist of two people.
Project development was hindered by the development of ICBMs
The first ready-made fighter the US military planned to receive by early 1963. At the same time, the Pentagon was ready to buy a new car in hundreds. According to initial plans, the US Air Force hoped to order immediately 480 F-108 fighters, which have already been given the official name Rapier ("Rapier"). However, this was not destined to come true. Already in September 1959, the project of creating a new heavy escort fighter was finally frozen, and in 1960, North American company finally stopped developing.
The new fighter was never built in metal, remaining forever at the stage of the wooden layout. The fate of the project was negatively affected by the constant increase in the cost of the aircraft, as well as increasing uncertainty about the prospects for strategic weapons. It was not clear which strategic bombers of the USSR should confront the new fighter with such a set of combat capabilities. At the same time, intercontinental ballistic missiles appeared on the scene, which became the main striking force of countries possessing nuclear weapons.
The layout of the fighter XF-108 Rapier
With the development of ICBMs, the need to use a “swarm” of strategic bombers, which could have been shot down when approaching a target, disappeared. At the same time, the appearance of more advanced guided cruise missiles, which could be launched from submarines and surface ships, also played a role in the closure of the XF-108 Rapier project. New types of missile weapons leveled the value and capabilities of the Rapier, which turned into an expensive toy without specific tasks. By 1960, the project was completely stopped.
However, it cannot be said that the XF-108 Rapier project for North American was completely useless. Many developments were later used to create both experimental and serial machines. In particular, the aircraft fuselage almost without changes migrated to the serial North American A-5 Vigilante supersonic carrier-based bomber, which embodied the concept of a supersonic aircraft with a more modest maximum flight speed - in the region of two Machs.