Hey guys.. I'm sure most of you heard about this type of engine: the propfan or unducted fan engine. For those of you who haven't, it's basically a mix of turboprop and jet engine. Biggest advantge is that has the fuel economy of a turboprop with the efficency of a jet at high speeds. This technology came up in the late 80s and basically didn't develop further due to the cost of fuel being very cheap, and the fairly high development costs. Off course, that was back when the jet fuel was about 1$/gal. We all know that even though the oil of barrel price went down this year, it is still not cheap and it could go up again. Remember that when the global economy crisis ends, economies like China, India and other SE Asia will resume, and demand will increase dramaticaly.
Why haven't this engine design come back? Fuel consumption is between 25-40% less than a turbofan. That was with 1980s technology, these days they could probably improve it even further.
This video is from 1989, and they keep talking about this engine as the future for comercial jets. If this engine would been in service last year with airplanes like the md-90, b717, or even 737 "NNG", I'm sure the oil crisis wouldn't have hit us so hard, specialy in the domestic market.
YouTube - Ultra High Bypass Jet Engine Green Technology Airline Flight Test