"Unmanned travel to other star systems is well within current technology, so long as you're not in a rush to get there."

Well, I'm not very patient. So is the public, which has to do the funding.

I guess an unmanned probe (possibly a fly-by) would have a chance if the target is interesting enough and the necessary amount not to big.

My initial interest in this topic is the question if it is entirely impossible to get to the nearest star system broadly within the lifespan of a human.

Assuming a lifespan of 100 years for the carefully choosen crew.
A take-of-age of 25 years, "retirement age" of 85 years (!).
I would even consider a 1 to 2 Generation Ship, with new born childs replacing the aging crew.
Time for the journey could be 60 - 100 years.

Thats why I figured an average speed of 4.4% c should be sufficient to reach alpha centaury during a manageable time frame.

The crew would have to transport every machinery to build and sustain a space faring society around the target star, enough genetic material to allow for a stable population.... lot's of transportation smile

"laser powered solar sails" have several advantages, but the main disadvantage would be the political ramifications of Multi-Terrawat-Lasers in space.

Additionally I would kind of prefer to have the engine on board rather then depending on people billions of km away to maintain the equipment.

So far the only remotely feasible concept, given my wishes, seems to be nuclear pulse propulsion.
However I calculate the needed masses/energies are always to big.

Even the nearest stars are awfully far away :-/