747400sp From United States of America, joined Aug 2003, 3624 posts, RR: 2 Posted (8 years 7 months 6 days 9 hours ago) and read 3844 times:
In 2001 Airbus was talking about a study for a widebody sst with high by pass turbo fans. This would have been a great ideal if they study it more. I heard that Airbus is working with Japan on there sst. Could this design be use in there work with Japan design. Do any body know what Airbus is doing with there sst design.
B2707SST From United States of America, joined Apr 2003, 1369 posts, RR: 59
Reply 3, posted (8 years 7 months 3 days 20 hours ago) and read 3682 times:
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.