If you look at the reactionless drive I linked to, and if it works and can be scaled up, and in the future we can have mini nuclear or fusion power plants, all

If you look at the reactionless drive I linked to, and if it works and can be scaled up, and in the future we can have mini nuclear or fusion power plants, all of which I see is possible, then the only problem remaining is collision on the way to the star and whether astronauts can peacefully stay on a small spacecraft for several years, knowing they are travelling in a one way time machine and people on earth will die quickly as they travel above c (technically their destination becomes closer, rather than them actually travelling this fast) from their frame of reference. I think it is not unreasonable to expect all of these problems resolved within 500 years, making space travel between stars a possibility for humanity.