|Quoting 747400sp (Thread starter):|
In 2001 Airbus was talking about a study for a widebody sst with high by pass turbo fans
This is a contradiction in terms; SSTs require low-bypass turbofans (or optimally no-bypass turbojets) for efficient supersonic flight. High-bypass fans are great for quiet takeoffs and landings and efficient cruise at Mach < 0.9, but their enormous frontal area and slow exhaust velocity destroy their efficiency at higher speeds. For Mach 2.4 cruise, expect a bypass ratio of at most 1.5-2.0, compared to 9 on the GE90 and 10-11 on the GEnx and Trent 1000.
Probably the biggest challenge in SST design is finding an engine that is both efficient in all three speed regimes (takeoff/landing, subsonic cruise, supersonic cruise) and quiet enough to meet Stage III/IV requirements. NASA couldn't do it on the HSCT less than ten years ago, and Rolls-Royce says they still cannot appreciably beat the Olympus on supersonic efficiency. Compare this with the tremendous advances that have been and are being made in subsonic turbofans and the economic case for the SST weakens even more.
Keynes is dead and we are living in his long run.