[6ppc]

Water is only the mechanism to transfer solar energy into motion.

Correct. The proper term for the water would be reaction mass, not fuel.

Regarding getting the water into orbit...chemical rockets would not be the way to do it. Freezing the water and launching it with electromagnetic rail guns or ground based lasers would be the way to go. If humans don't have to go along for that ride there would be no limit on how many gees the launch system could generate.

[thackney]

As long as we are dreaming about the future, we might as well go full “Arthur C. Clarke” and install his Space Elevator.