You're close, Sarge. The problem with these engines is the thrust to weight ratio. An internal combustion engine such as a turbine or a gasoline-driven piston engine has a superior work-to-weight ratio than any external combustion (steam) engine does, because the latter must use an extra transfer fluid to get heat to the output side where it is used to do the work. This adds a lot of extra weight. Note the airplane in this example does not make a cross country demo flight, only a short flight because it needs water fairly often. Although theoretically you could make a steam engine that loses little or no water it is not an economical proposition. Steam locomotives have to carry large quantities of water onboard and even so they have to stop every so often and reload the water tanks. Internal combustion does away with this extra stage and the combustion mass itself acts as the heat transfer medium. The advantage of steam engine lies in its higher efficiency in terms of waste heat energy and entropy increase, but they are heavier and the tradeoff is not worth it for weight-sensitive machines like airplanes. They are also slower to wind up and spool down because of the additional heat transfer medium involved in the system. For an airplane, train, or an electric plant it's not that crucial and if you plan ahead enough you can work around the delay. Generally steam engines are not ideal for transportation machinery and this is why they are seldom used for anything that travels.