Slowrotor,
I certainly make no claims against your steam turbine design experience, but it's the "lightweight condenser" bit i'm not convinced about. Heat exchangers always end up large and heavy for a given power transfer. Look at your car radiator if you don't believe me, it will be designed to sink about the same heat power as your engine propshaft power (with 50 to 100 celcius temp difference). I know how much effort the radiator suppliers go to to minimise size/mass, and in this case the working fluid starts as a liquid.
I put that steam aircraft link in for interest, since like link provided by usmc_helo, it contained good general interest content. If the design is a tip jet, then by definition it has to be a total loss system anyway, which means air has to be the working fluid. There may well be better concepts out there, but turbines and recips work - every day, and for many 1000s of hours.
My interest is purely wether the function of turbine compressor and tip jet can be combined into the rotor system. The motive is really to provide an alternate against which to compare the idea of coanda effect tail jet mixer, for future Notar concepts. I just realised that there may be a side benefit of powertrain complexity/cost reduction for tip jet, so wanted to see what problems had already been found. Think of it as scoping out a possible future CFD project - gotta get up to speed sometime.
Mart