Time dilation and space contraction only matter if you can reasonably achieve speeds of a significant portion of the speed of light. AFAIK nobody has even come up with a reasonable way to achieve this for lightweight probes, let alone for hundred-ton ships capable of carrying humans. And let's not forget the practical problems like all photons incoming from the front being blueshifted into ultrahard radiation that would make a point blank nuclear bomb seem like a small candle.
Realistically even getting to the nearest star in less than 400 years experienced time is way way WAY out of reach for now.
Realistically even getting to the nearest star in less than 400 years experienced time is way way WAY out of reach for now.