DERG & Bear
* Open Rotor: Last fall, GE announced a joint study with NASA related to an open rotor or unducted fan engine design. In the 1980s, GE successfully ground-tested and flew an open-rotor engine that demonstrated dramatic fuel savings. Since then, GE has advanced its data acquisition systems and computational tools to better understand open-rotor systems. GE also gained extensive experience with composite fan blades in its GE90 engine and GEnx engine"
Her is a link to a site, "Then and Now:
YouTube - Family tree
Interestingly, the turbine mid-frame (location similar to that of the IP/HP frame in the Trent 900) that had been removed on the CF6-80C2 engine, returned on the GE-36 UDF as it was the main support for the propulsors (fan blades). It was a much different design and it was an extremely complex structure, never fully refined before the project ended. IMO, there were some vibration problems that existed that needed to be eliminated.