I was thinking. It could be possible with investment casting to utilize inexpensive stereo lithographic 3d printers to make cheap aluminum alloy combined cycle turbines. Software could create a turbine based on parameters you give it. Say you want a turbine that will have 35% efficiency and give you 1000 newton-meters of torque complete with a perfectly sized shaft. It could output some kind of object file like .obj to be sliced for 3d and printed on a cheap lcd resin printer. Use the form as an investment casting for an aluminum alloy. The design could introduce water injectors for lowering the temperature of the combustion gasses while expanding them.