RN nuclear-powered surface ships?

[Hobbes]

Doesn't work that way, mate. Separating water into hydrogen costs more energy than you can recover by putting the hydrogen into a fuel cell (or an internal combustion engine, for that matter). You'd run out of juice pretty quickly.  

[SimonR]

uhuh. And the hydrogen converter is powered by, what?  :dum:

Well, once it's started it powers itself, right     Not really a perpetual motor but close.

The theoretical maximum efficiency of hydrogen extraction by electrolysis [ 2H2O(aq) + electricity → 2H2(g) + O2(g) ] is only about 80%. In real life applications it's between 50% and 70%. So a sea fuelled hydrogen powered ship would only be feasible if supplemented by galley slaves manning the oars.    

[kitnut617]

Doesn't work that way, mate. Separating water into hydrogen costs more energy than you can recover by putting the hydrogen into a fuel cell (or an internal combustion engine, for that matter). You'd run out of juice pretty quickly.

Well I was watching this thing on Discovery Channel a week or so ago -------