A method and apparatus to heat-activate hydrogen of water for powering rotational, reaction-thrust and projectile-expulsion embodiments (19, 60, 61, 75) of a water engine (10) with hydrogen energy of water which is spray-atomized and electrically heated internally in one or more hydrogen activators (1). Water-hydrogen electrons of the spray-atomized water are heat-activated up to exponentially greater output heat-activation energy than input activation-heat energy added electrically with power generated from forms of the water engine. A minor portion of the output heat-activation energy of the water hydrogen is utilized for generating electrical current for the input activation heat of the spray-atomized water in the hydrogen activators. Net output heat-activation pressure of water-hydrogen is directed from one or more of the hydrogen activators to one or more use chambers (9) of universal-use forms of the water engine. Rotational features of the water engine preferably employ a turbocam drive (20).