scramjet

A scramjet, or supersonic combustion ramjet, is a type of jet engine designed for supersonic flight speeds. Unlike traditional ramjets that slow the incoming air to subsonic speeds before combustion, scramjets burn fuel in a supersonic airstream. This is crucial for very high Mach numbers (Mach 4 or 5 and above) where slowing the air would cause significant pressure losses.12

Scramjets are characterized by their simplicity, lacking the rotating machinery found in turbojets. They are projected to use fuels like hydrogen or methane, which can also serve as a coolant for the high-speed engine and aircraft structure. The engine's design involves external surfaces for deceleration and acceleration, with the combustion chamber being the core component.2