This isn't convincing. The turbofan is a good idea because the propulsive efficiency is better than a turbojet. The Stipa is a ducted fan, but the resemblance

This isn't convincing. The turbofan is a good idea because the propulsive efficiency is better than a turbojet. The Stipa is a ducted fan, but the resemblance to a turbofan is superficial. https://en.wikipedia.org/wiki/Turbofan#Principles https://en.wikipedia.org/wiki/Turbofan#Principles