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Supercruise is the ability of an aircraft to fly at supersonic speeds without the use of an afterburner. In practical terms, an aircraft is considered capable of true supercruise only if it can operate at supersonic speeds while carrying a useful cargo load. Supercruise-capable aircraft have been put into service in both civilian and military roles. The ability to break the sound barrier without relying on the extended use of afterburners greatly increases the fuel efficiency of supersonic flight and eliminates many of the tactical drawbacks of afterburner flight in a combat setting.
For much of the history of supersonic aviation, speeds exceeding Mach 1 — or the speed of sound, 1,126 feet (343.2 m) per second — required the use of an afterburner system. An afterburner injects fuel into the jet exhaust of an engine after it has already passed through the jet turbine, greatly increasing the heat and pressure within the jet pipe and resulting in a stream of jet exhaust that has a much higher exit velocity. The drawback of such a system is that it burns fuel at a rate several times higher than that of normal operation. An aircraft that is capable of utilizing tactically significant afterburner duration suffers from an increased fuel fraction, the ratio of the craft's loaded weight that must be dedicated to carrying fuel. It also creates a large, hot plume of exhaust gas that makes the aircraft more visible to infrared sensors, increasing the range at which the aircraft can be easily spotted by enemies.
A supercruise aircraft generally utilizes afterburners to accelerate from subsonic to supersonic velocity, although this is because of concerns about fuel efficiency rather than strict necessity, in most cases. While breaking the sound barrier, an aircraft is subjected to drag-inducing forces caused by flying within its own sonic boom, making it more difficult to accelerate further. After the aircraft has reached Mach 1.1, or 1.1 times the speed of sound, it is no longer subject to these forces and acquires a much more efficient flight profile. By using an afterburner to minimize the amount of time spent overcoming sonic shock, a supersonic aircraft can save fuel over the length of the entire flight, even allowing for the increased fuel use of the afterburner.
The Concorde supersonic transport jet routinely utilized supercruise in transatlantic flight, cutting transit time roughly in half in comparison with subsonic jetliners. The F-22/A Raptor was the first military aircraft designed with sustained supercruise capabilities, although some earlier fighters were capable of limited supercruise with specialized loadouts. Many next-generation jet fighters have been designed to reduce their reliance on afterburner systems for supersonic flight, because supercruise capabilities are considered a necessary component of modern air superiority.
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