I think interstellar travel at a sizeable fraction of light speed is quite feasible. There are solar sail technologies which could act as a motor and a brake. But they have to be light. We could make molecular level carbon circuits which would be extremely light, energy efficient, and radiation hard. Indeed, it may be easier for craft like that to go to the nearest stars and come back again, rather than try and beam information on what they found back to earth.
How to we get humans there? It would be easier to take human genetic material than to take living beings, even in suspended animation. The Japanese are working on humanoid robots to look after the elderly, so it is not a huge leap to suggest they could act as surrogate parents. All we need to take is the tiny maker bot with instructions to make the colony and then the people to live in it. I am not saying this is an ethical thing to do, but it is a better option than shutting two generations of families in a generation ship so the third might see their possibly barren destination. We don’t have the technology, but only 66 years separates the Wright brothers and Apollo 11.
In the sixties, everyone felt that going to Mars and Venus, then the outer planets, then the stars was inevitable (remember, we were supposed to be out at Jupiter by 2001). Now, we are wondering what the payback is. We aren’t going to come back with gold, tobacco, and slaves. We aren’t going to stay there, and spread the Empire. By the time the third generation gets there, they won’t be ‘us’, they will be ‘them’. And we haven’t been back to the Moon, since.
PS: I don’t buy the idea that we need to spread humanity to survive. In the very long-term, yes, maybe. But none of the giant meteors killed All Life. For humans to go extinct, you would have to kill all the ones in bunkers in Switzerland, North Korea, and North Dakota. Mankind has been reduced to very small numbers before, and we are still here.
