Traditional jet engines, both civil and military, are known as two-stream turbofans. When air flows into the engine’s inlet, it is divided into two separate streams: the core stream and the bypass stream. The core stream flows directly into the engine’s core, where it is mixed with fuel, combusted, and expelled as a hot, high-velocity jet. The other stream, known as the bypass stream, is directed around the engine’s core and accelerated by the hot gas, providing additional thrust. The disparity between these two airstreams is referred to as the engine’s bypass ratio.
High-bypass engines are typically used in commercial airliners. While they provide comparatively lower power, they are extremely fuel-efficient, especially at subsonic speeds, making them great for cheap mass transportation at scale. Military fighter jets, on the other hand, prefer low-bypass engines. With more fresh air flowing through the engine’s core, these engines can provide much higher thrust, better performance at supersonic speeds, and enable the use of an afterburner. In exchange, fighter jets are notoriously fuel-hungry.
Adaptive engines like the XA100 and XA103 are designed to combine the best of both worlds into a single package. They can reconfigure themselves in mid-flight to better suit the flight profile. For instance, when the jet is cruising at subsonic speed, the engine can be optimized for maximum fuel efficiency and range. In combat situations, it can adapt for maximum thrust and supersonic performance, just like a conventional fighter jet engine.
