Ethics of Interstellar Travel Nuclear Fission is not powerful enough, nuclear fusion is always 50 years away and, besides, each of these have limitations due to the fuel needing to be carried aboard.
Then there is the issue of speed and distances involved. To be able to travel such vast distances in ny kind of plausible way (I will expand in what I consider as "plausible" later), the speed would need to be a significant fraction of the speed of light. Putting aside the technical difficulties in achieving such speed given the above limited energy sources and consequent technologies, there is a deeper, more intractable problem and that is the fact that "empty" space, particularly for large bodies of matter travelling at high speeds, is not empty.
In each cubic metre of space, there are, on average a few free floating, lone hydrogen atoms as well as other elements and larger, more complex, cosmic dust particles. For anything travelling at a tiny fraction of the speed of light, these particles may as well be assumed to be non existent in practical terms. But, for objects travelling at significant fractions of the speed of light they are anything but non existent. If we assume a large space craft travelling at a significant fraction of the speed of light, the issue of friction and build up of heat is going to be a problem.
The only other viable system that has been conceptualized would be the Buzzard Ram jet whereby free hydrogen is harvested on route from the interstellar medium I alluded to above. This is still firmly in the realms of science fiction and there is no good reason to assume it will not remain there.
To return, now, to the issue of what is a plausible time-span for travel to another world. If we are talking about a multi-generational time-span, the following issue arises: the spaceship would need a fully functioning, ecologically self contained and self sustaining living system whereby all waste products of life were recycled and returned to the system for reuse. Here, on earth, we have an entire planetary eco system devoted to that little task. In what realms of fantasy does anyone suppose it would be possible to create a fantastically miniaturized, version of the above - where all of the energy required for such a complex living system to exist and to renew and repair itself would have to be carried on board for the entire journey?
There are other issues of plausibility, but I'll leave it at that one since it is quite insurmountable enough as it is. Put it this way, if humans were capable of devising a space vessel capable of the above, there would be little requirement to endure the arduous interstellar journey to the next star since humans could colonize empty space in our own solar system far more easily on the back of such technologies. But, even that is highly improbable.
Our future is not in the stars. It is in the mud.