Re: Boiler Pressure

James raised a great point about how you need forward and reverse turbines, probably the reason the only direct drive turbine locomotive we ever saw for use in U.S. was the Pennsy S2. It had a 6,000 HP forward turbine but only had a 1500 HP reverse turbine. Steam turbine electrics had the advantage of being completely reversible and probably had less thermodynamic losses in transfering the power from the shaft to the wheel as well.
I have been told that propulsion systems on modern nuclear submarines and air craft carriers use the steam turbine electric principal, probably , again for the same reason.
Regards,
Trevor H.