Space Propulsion

[Anomalocaris]

Problem is, I think the laws of physics, the vast (and increasing) distance between us and our stellar neighbours in the cosmos, and our finite lifespans may stump man's attempts at deep space exploration every time.

It maybe a futile venture, but to persist boldly in the face of insurmountable challenges is what makes us human, and how we've achieved anything worthwhile to begin with.

I think the ultimate barrier is socialogical, not technological. If we were to discover that no faster than light travel is ever possible, it is still possible from technological perspective to get to another star, or even another galaxy. It just taqkes a long time. But the time required is not long compare to typical length of a species' existence. So it is well worth doing if species survival requires it.

Humans are conditioned by evolution to focus its world view on five generations, two behind, two ahead, with heavy emphasis in the middle. Geological time is alien to us. This heavy shape our sociology and psychology. Which is why biblical fundamentalists do not feel themselves to be stupid.
The main limitation is whether humanity can adapt its sociological outlook to sponsor projects on the time scale of thousands or tens of thousands of years required, given a undeniable requirement for such projects if our species were to survive.