Comment by AngryData

If we solve fusion to the point where it is easy in a relatively light reactor or manage to "safely" contain significant amounts of antimatter, it is possible to travel the stars by maintaining 1g acceleration for years or decades. But of course maintaining 1g acceleration for even just an hour, not to mention years, while theoretically possible, is still so far outside of practicality that I don't expect to see any practical plans for it in my life time.

The only currently feasible solution currently is to ride a wave of sequential nuclear bomb explosions, but that is far from ideal.

So the possibility still exists, current physics is a big obstacle to challenge, but is not a solid barrier preventing our expansion in the far future.