So I'm working on a thesis project at the moment designing an airship, and I've run into a bit of a stumbling point. I'm wondering if it would be possible to have a propeller that works to produce propulsive power when it needs to fly, but when the craft is tethered could operate as an electricity-generating wind turbine. The electrical system is definitely capable of it, but what I'm unsure about are the mechanicals (i.e. the gearbox and operational rpm ranges for both different applications), and more importantly the aerodynamics. I've read that ducted fans are more efficient for propulsion, but to be honest, I'm not exactly sure why. Obviously the effects of the duct on the aerodynamic flow around the propeller would have a big impact on the efficiency of it as a generator, and I'm not sure whether they would be positive or negative. I have some reading to do on actuator disc theory and fluid dynamics, but I must say I'm in over my head (I'm an industrial designer, not an engineer, by trade, so this entire thesis has been a serious crash course in the fun math and physics side of things). At the moment I'm not too overly concerned about the specifics so much as a basic idea of whether or not it's feasible. I greatly appreciate any help, and thanks in advance!