Comment Re: increases exponentially (Score 1) 272
Actually we do. A few meters of water or other hydrogen-rich substance. Very low-tech, but heavy. But a generational spaceship would inevitably be heavy, and would need a very large reservoir of water anyway. The water would not have to be hauled up from Earth, there is plenty of it in the outer solar system, in icy moons. Possibly even in our own Moon. By the time building generational starships becomes feasible, accessing extraterrestrial water resources is probably routine.