Supercruise is sustained supersonic flight of a supersonic aircraft without using afterburner (also known as "reheat"). Many supersonic military aircraft are not capable of supercruise and can maintain Mach 1+ flight only in short bursts with afterburners. Aircraft such as the SR-71 Blackbird are designed to cruise at supersonic speed with afterburners enabled.
Some fighter jets are capable of supercruise but only at high altitudes and in a clean configuration, so the term may imply "a significant increase in effective combat speed with a full weapons load over existing types". [1] One of the pre-eminent military examples of supercruise is the F-22 Raptor, for which supercruise was defined as "the ability to cruise at speeds of one and a half times the speed of sound or greater without the use of afterburner for extended periods in combat configuration." [2]
One of the best-known examples of an aircraft capable of supercruise, and the only notable non-military example, was the Concorde. Due to its long service as a commercial airliner, Concorde holds the record for the most time spent supersonic; more than all other western aircraft combined. [3]
A few early supersonic aircraft attained speeds just beyond the speed of sound without using afterburning.
On 3 August 1954, a Gerfaut research aircraft powered by an SNECMA Atar 101D2A engine exceeded Mach 1 in level flight without using afterburning. [4] [5]
The first production aircraft to exceed Mach 1 in level flight without afterburning was the Lockheed F-104 Starfighter after its J65 engine was replaced with a J79. The maximum speed without afterburning was Mach 1.05. [6]
The P.1 prototype of the English Electric Lightning, powered by non-afterburning Armstrong Siddeley Sapphire engines, exceeded Mach 1 on 11 August 1954. A week previously, on 4 August, the P.1, WG760 flown by Roland Beamont on its maiden flight, had unknowingly exceeded Mach 1 in a climb. [7] During development testing at English Electric it was established that the Lightning had a stabilized speed capability in level flight, without afterburning, of about Mach 1.2 and for the T.4 (2-seat trainer) 1.08. [8] Flying just above the speed of sound without using afterburning, although done by the contractor as part of some flight trials does not appear to have been relevant to the operational capability of the aircraft. Service trials established intercept profiles for subsonic and supersonic targets at different altitudes with subsonic cruising at a maximum of Mach 0.95 with all supersonic speeds beyond subsonic cruise attained with afterburning. [9]
All the Fairey Delta 2 initial supersonic test flying to Mach 1.1 was done without afterburning. Selecting the afterburner, which initially only had a maximum selection with no intermediate positions, would have caused an uncontrollable rapid acceleration to potentially hazardous speeds; i.e., too far beyond previously established flutter-free speeds. [10]
Only the supersonic transports (SST), Concorde, and the second version of the Tu-144 (the Tu-144D) spent most of their time cruising at their design speeds without needing afterburning. Afterburning was added to Concorde for take-off to cope with weight increases that came after the initial design. It was also used to accelerate through the high-drag transonic speed range, not because the extra thrust was required, but because it was available and improved the operating economics. The redesigned Tu-144D used engines with no afterburners which, together with other improvements, increased the full payload range from 3,080 to 5,330 km (1,910 to 3,310 mi) (Concorde's operational range was 6,470 km or 4,020 mi). [11]
The United States Air Force set supercruise as a core requirement for the Advanced Tactical Fighter program, [12] which resulted in the F-22 Raptor. The F-22 Raptor's supercruise capabilities are touted as a major performance advantage over other fighters, with supercruise being demonstrated exceeding Mach 1.5. [13] [2] Supercruise capability provides advantages for stealth aircraft because an afterburner plume reflects radar signals and creates a significant infrared signature. [14] Virtually all fighters prior to the F-22 cruise at Mach 0.8–0.9 while carrying a normal weapons load. [1]
There are a few engines in production that are designed to facilitate tactically significant supercruise:
Independently, Russia is working on izdeliye 30 (after AL-31F and AL-41F derivatives modifications, like izdeliye 117S turbofan) and RD-33MKRU Morskaja Osa; an all-new AL-41 engine with a complete redesign is underway to add supercruise ability to the Sukhoi Su-57. This has yet to bear fruit, but the stop-gap 117S engine, produced by this program, may achieve the supercruise goal already. While testing a Su-35BM fighter equipped with these engines, it managed to accelerate past Mach 1 without using the afterburner, suggesting that it had supercruise capability. It has yet to be seen whether this will be possible with a combat load. [24]
Aircraft | Supercruise speed | Production Year | Service status |
---|---|---|---|
Sukhoi Su-57 [25] | Mach 1.30 | 2020 | In service |
Dassault Rafale [15] | Mach 1.40 [26] | 1986 | In service |
Eurofighter Typhoon [16] | Mach 1.50 | 1994 | In service |
Saab JAS-39E Gripen [22] | Mach 1.10 [23] | 2019 [27] | In service |
General Dynamics F-16XL [28] | Mach 1.10 | 1982 | Retired (prototype) |
Lockheed Martin F-22 Raptor [13] [2] | Mach 1.80 | 1996 | In service |
Lockheed YF-22 [29] | Mach 1.58 [30] | 1989 | Retired (prototype) |
Northrop YF-23 [29] | Mach 1.72 [31] | 1989 | Retired (prototype) |
Concorde [32] | Mach 2.02 [33] | 1965 | Retired |
EWR VJ 101 | Mach 1.04 [34] | 1962 | Retired (prototype) |
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s. Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic. Flights during which only some parts of the air surrounding an object, such as the ends of rotor blades, reach supersonic speeds are called transonic. This occurs typically somewhere between Mach 0.8 and Mach 1.2.
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).
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 a turbine. The compressed air from the compressor is heated by burning fuel in the combustion chamber and then allowed to expand through the turbine. The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany, developed the concept independently into practical engines during the late 1930s.
The English Electric Lightning is a British fighter aircraft that served as an interceptor during the 1960s, the 1970s and into the late 1980s. It is capable of a top speed of above Mach 2. The Lightning was designed, developed, and manufactured by English Electric. After EE merged with other aircraft manufacturers to form the British Aircraft Corporation it was marketed as the BAC Lightning. It was operated by the Royal Air Force (RAF), the Kuwait Air Force (KAF), and the Royal Saudi Air Force (RSAF).
The fourth-generation fighter is a class of jet fighters in service from around 1980 to the present, and represents design concepts of the 1970s. Fourth-generation designs are heavily influenced by lessons learned from the previous generation of combat aircraft. Third-generation fighters were often designed primarily as interceptors, being built around speed and air-to-air missiles. While exceptionally fast in a straight line, many third-generation fighters severely lacked in maneuverability, as doctrine held that traditional dogfighting would be impossible at supersonic speeds. In practice, air-to-air missiles of the time, despite being responsible for the vast majority of air-to-air victories, were relatively unreliable, and combat would quickly become subsonic and close-range. This would leave third-generation fighters vulnerable and ill-equipped, renewing an interest in manoeuvrability for the fourth generation of fighters. Meanwhile, the growing costs of military aircraft in general and the demonstrated success of aircraft such as the McDonnell Douglas F-4 Phantom II gave rise to the popularity of multirole combat aircraft in parallel with the advances marking the so-called fourth generation.
An afterburner is an additional combustion component used on some jet engines, mostly those on military supersonic aircraft. Its purpose is to increase thrust, usually for supersonic flight, takeoff, and combat. The afterburning process injects additional fuel into a combustor in the jet pipe behind the turbine, "reheating" the exhaust gas. Afterburning significantly increases thrust as an alternative to using a bigger engine with its attendant weight penalty, but at the cost of increased fuel consumption which limits its use to short periods. This aircraft application of "reheat" contrasts with the meaning and implementation of "reheat" applicable to gas turbines driving electrical generators and which reduces fuel consumption.
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The Advanced Tactical Fighter (ATF) was a program undertaken by the United States Air Force to develop a next-generation air superiority fighter to replace the F-15 Eagle in order to counter emerging worldwide threats in the 1980s, including Soviet Sukhoi Su-27 and Mikoyan MiG-29 fighters under development, Beriev A-50 airborne warning and control systems (AWACS), and increasingly sophisticated surface-to-air missile systems. The ATF would make a leap in performance and capability by taking advantage of emerging technologies, including advanced avionics and flight control systems, more powerful propulsion systems, and stealth technology.
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The Lockheed/
The Lockheed Martin/Boeing FB-22 was a proposed supersonic stealth bomber aircraft marketed to the United States Air Force. Its design was derived from the F-22 Raptor stealth air superiority fighter. Lockheed Martin proposed its unsolicited design in the early 2000s as an interim "regional bomber" to complement the aging U.S. strategic bomber fleet. Lockheed Martin suspended work on the concept following the 2006 Quadrennial Defense Review, which called for a new and much larger strategic Next-Generation Bomber by 2018; this program would eventually morph into the Long Range Strike Bomber.
The General Electric J79 is an axial-flow turbojet engine built for use in a variety of fighter and bomber aircraft and a supersonic cruise missile. The J79 was produced by General Electric Aircraft Engines in the United States, and under license by several other companies worldwide. Among its major uses was the Lockheed F-104 Starfighter, Convair B-58 Hustler, McDonnell Douglas F-4 Phantom II, North American A-5 Vigilante and IAI Kfir.
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An intake ramp is a rectangular, plate-like device within the air intake of a jet engine, designed to generate a number of shock waves to aid the inlet compression process at supersonic speeds. The ramp sits at an acute angle to deflect the intake air from the longitudinal direction. At supersonic flight speeds, the deflection of the air stream creates a number of oblique shock waves at each change of gradient along at the ramp. Air crossing each shock wave suddenly slows to a lower Mach number, thus increasing pressure.
The Volvo RM8 is a low-bypass afterburning turbofan jet engine developed for the Saab 37 Viggen fighter. An augmented bypass engine was required to give both better fuel consumption at cruise speeds and higher thrust boosting for its short take-off requirement than would be possible using a turbojet. In 1962, the civil Pratt & Whitney JT8D engine, as used for airliners such as the Boeing 727, was chosen as the only engine available which could be modified to meet the Viggen requirements. The RM8 was a licensed-built version of the JT8D, but extensively modified for supersonic speeds, with a Swedish-designed afterburner, and was produced by Svenska Flygmotor.
The Boom Symphony is a medium-bypass turbofan engine under development by Boom Technology for use on its Overture supersonic airliner. The engine is designed to produce 35,000 pounds of thrust at takeoff, sustain Overture supercruise at Mach 1.7, and burn sustainable aviation fuel exclusively.
Despite the greater frontal area the Gerfaut remains a level-supersonic aeroplane without afterburning, although the engine is now so equipped.
More significantly, it can supercruise in dry power, even with four missiles and a belly drop tank.
The aircraft is capable of cruising at around Mach 1.8 without afterburners and has a top speed of around Mach 2.2.
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