To supercruise is an aviation term. An aircraft that can supercruise is able to attain and maintain supersonic level flight without using afterburners. The first U.S. fighter to supercruise will (theoretically) be the F-22 Raptor Advanced Tactical Fighter, currently in low-rate production.

The SR-71 Blackbird engines were almost entirely afterburning, especially for takeoff. The nacelles themselves (not the J-58 jet engines in them) provided nearly all the thrust at high speeds; the inlet spike and nacelle mouth 'shaped' the airflow into precise shockwaves of high supersonic speed. The fuel burn outside the engine, in the nacelle (afterburner) made the nacelle into a 'near-ram-jet' with the engine mostly getting in the way.

WolfKeeper provides needed correction: the Concorde (and its Soviet counterpart the Tupolev 144) did, in fact, have supercruise. The Concorde, however, used 'low-level augmentation' - essentially, afterburners - during takeoff and in order to accelerate past Mach one - in order to spend as little time as possible in a high-drag flight regime. Although afterburners use more fuel, the ability to quickly traverse these less-efficient flight regimes meant an overall fuel savings, and the Concorde would then turn off reheat and supercruise at its normal Mach two without afterburners.

Supercruise is the capacity of a jet fighter to sustain supersonic flight. The current generation in fighters, which includes the MiG-29 and F/A-18 Hornet can attain supersonic speeds. However, such speeds are only attained using the afterburners. Afterburners operate more or less by spraying fuel in the hot exhaust of a jet engine. High thrust can be attained, but at the cost of high fuel consumption. An hour's worth of fuel can be burned in a minute. No current jet fighter can sustain supersonic flight for this reason. All are subsonic aircraft with a limited supersonic capability.

Supercruise capability represents a leap as substantial as the move from propellers to jets. Tactically, this offers significant advantages, as the supercruise capable aircraft enters combat at a high energy state. US Fighter doctrine teaches that speed is life! Speed greatly complicates any interception problem. Weapons launch windows are greatly shrunk. Subsonic fighters may be able to attain equal, or greater speeds than a supercruise aircraft, but the acceleration times required to attain such will make that point moot in most tactical situations. Supercruise capable aircraft will enjoy the choice to engage or not engage in most situations. The sum of these capabilities grant supercruise capable aircraft distinct tactical advantages over all current fighters.

An aside, the SR-71 is in effect a ramjet, because the operation of its nose creates a ramjet effect, reducing its fuel consumption to roughly equal the 737. Jet engine inlet design is quite a challenge, and particularly so for a supercruise aircraft. The reason is that air entering a jet engine, must always travel at subsonic speeds, regardless of aircraft speed. Otherwise compressability waves--- or shock waves-- will create uncontrollable vibrations among the compressor vanes. Engine inlet design thefore can effectively limit the speed of the aircraft, regardless of thrust. The SR-71's distinctive, but not unique- nosecone is designed to funnel air around the J-58 engine for that very reason.

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