> On a nuclear powered ship (submarine or surface) there is plenty of energy
> available, so that technique could be used. But still, it would probably
> cheaper for a nuclear powered surface ship to store fresh water obtained
> on-shore sources than it would be to make fresh water from seawater.
Actually, virtually all Navy vessels of any significant size use this approach, whether they are nuclear powered or not. It is probably a bit more expensive than just storing water for short trips, but the power requirements aren't all that large compared with what you're burning to move the ship.
Billy Brown, MCSE+I