I think most of the text of these edits isn't useful for the article. A more appropriate version would be a short table listing the specific impulse or exhaust velocity for a variety of engines, a reasonable maximum cruising speed, and a flight time to Alpha Centauri, if the information is included at all. A fair bit of the interstellar travel article could stand editing; if I find myself with time on my hands, I may do a rewrite, but for now, the current version looks fine.