Addendum to 1): Thinking a bit further, just because we can produce a high amount of energy that doesn't necessarily mean we can automatically convert it into

Addendum to 1): Thinking a bit further, just because we can produce a high amount of energy that doesn't necessarily mean we can automatically convert it into kinetic energy for a space ship very well. Most propulsion systems in space still require expelling a propellant and conservation of momentum means this is unlikely to change. (Sure, one could imagine solar sails but the little momentum exchanged there won't get half of humanity to Proxima Centauri very fast.) So while we might have unlimited energy we might still be constrained by momentum requirements. The only way I can see to solve this conundrum would be producing enough propellant on board the space ship, e.g. (lots of) photons, using a laser. Definitely not impossible (especially not at these energy levels) but it'll be interesting to see what these propulsion systems will look like exactly. :) Ideally, we would of course try to use the propellant to also get rid of the waste heat mentioned earlier but I'm not sure whether this would work entropy-wise.