Quote Originally Posted by ShadowRaven View Post
Er, I'm not quite sure about that. First off you don't mention any necessities; how are you going to feed an entire city in space? Scrap that; where's the oxygen going to come from? If the answer to both those questions is gardens, likely 75%+ of the ship will need to be nothing but plants. Also, for any long-term mission like the one you're describing, it becomes imperative that we find some source of artificial gravity. And electricity? If you're going outside the bounds of our solar system, then solar power might not be reliable.

So in a way, you are right. We do have the technology to get there. But human interest in getting there is only one in long list of problems we've got going before such a mission becomes viable.
Obviously the entire city wouldn't be people and roads and buildings, it would mostly be dedicated to life support and essential equipment. Artificial gravity could be achieved through a variety of means, for example centrifugal force of a rotating compartment. Considering people would only be living in 25% of the ship, most likely something around 10-15%, it's not like we'd have to rotate a massive part of the ship. Electricity should be rather obvious considering it's a nuclear powered space ship.

The point is these aren't problems that can't be solved now. It's not like we need to perfect fusion technology or master wormholes before it's possible, we just need to work on the practical aspects and raise the funds and international interest. That's the biggest issue, a project like this is too big for any one nation to perform.