For the many reasons identified by others contributing to this discussion, the reciprocating steam engine powered by a fire-tube boiler undoubtedly came close, if not reached, the pinnacle of its technological potential. Sure exotic materials could perhaps gain a bit here and there with rust, fly ash erosion, work-hardening, embrittlement and the like, but the financial bottom line probably would not change enough to warrant the added developmental and manufacturing costs. The only steam-powered locomotive that came close to making economic sense was N&W’s “Jawn Henry.”

The mammoth Baldwin-Lima-Hamilton experiment with a steam-turbine electric locomotive, powered by a 600 psi naval water-tube boiler almost made it. In the 1950s, the accepted control system for water-tube boilers was the Bailey Meter system. Bailey Meters were widely used in stationary power plants and aboard marine vessels. It was a state-of-the-art electromechanical control system to regulate water supply, firing rates, and boiler output which was never intended to be used on a rocking, rolling, vibrating, slamming and shaking platform that occasionally (albeit briefly) took hits that exceeded 3 Gs. The Bailey Meters were literally – and frequently – shaken to pieces.

But from the 5,000 hp steam-turbine-driven generator on, the Jawn Henry was technologically the equal of any diesel locomotive of the day. All modern advances in locomotive electrical technology would be as applicable to the Jawn Henry today as to any diesel locomotive. If memory serves me, the N&W gave up on the Jawn Henry when the turbine failed. Here again, there have been substantive improvements in stationary and marine steam turbine technology in the last 50 years.

Sure the Jawn Henry had design problems. Coal was carried in a bunker forward of the cab. Not only did visibility suffer, but as the coal was consumed, weight on the forward trucks decreased and the front trucks became slippery. So, for example, move the cab forward (like a diesel) and as the coal load decreases, transfer water from the tender to tanks around the bunker (Having been aboard it while still at Baldwin, I can testify the engine was huge and there could be room for sizeable tanks). The Zeolite water treatment system mounted in the tender also took up a lot of room. Presumably (but I don’t know for a fact), there have been similar technological improvements to water treatment in five decades. Today's MIL-spec, ruggedized solid state technology would completely eliminate the Bailey Meter problem. And lastly, the naval boiler was fired with a movable grate system that introduce “green” (i.e., un-burned) coal at the upper end of the firebox and dumped ashes as the grates moved out of the firebox at the lower end. The moving grate system has the potential to be converted to fluidized bed combustion system that would materially decrease pollutant emissions.

Would today’s technology have permitted, or encouraged, the railroads to adopt the Jawn Henry? Who knows? And likely we will never know.