Engines for Supersonic Civil Transport Aircraft: Design Problems Associated With Flight in the Mach 2 to 3 Range

Because of its high overall pressure ratio and good propulsive efficiency, the jet engine is very efficient for supersonic propulsion. A high thrust per unit power plant frontal area and per unit weight are primary requirements and these imply high combustion temperatures. For a Mach 2.0 aircraft, engine design problems other than this are not outside existing experience but additional problems, such as bearing cooling, become more serious at cruise Mach Numbers approaching 3.0. A variable intake is essential and the method of geometry variation and control requirements are described. Variable propulsion nozzle design is also an area of vital importance and it is not claimed that an entirely satisfactory solution, giving good performance with low drag in the transonic phase, has yet been achieved. The ‘sonic boom’ phenomenon can have an important influence on engine design, in that it may determine the maximum altitude at which the aircraft has to fly subsonically. Should this be appreciably above the tropopause, then it will not only influence the amount of thrust installed but may also dictate the fitment of reheat for the transonic acceleration. Take‐off noise is a requirement which can influence both the installed thrust and the choice of engine type. Despite the lack of firm standards for field noise and ‘coast‐over’ noise, there is good reason to believe that the noise levels of a supersonic transport need not exceed those of the quieter long‐range subsonic transports in service at this time.