Physical optics are the ' active optics ' of the time of the speed of light.
Generation ships in science fiction are plot devices from the early days of the genre, when it was discovered that the speed of light was an absolute maximum.
Modern sci-fi just throws out the speed of light as a limiting factor, plugs in a term like 'hyperspace' or 'warpspeed', and the need for Generation Ships is overtaken by events.
These drives allow a craft to travel beyond the speed of light.
These elements are coupled with high speeds to propel the vehicle fast enough to transcend the speed of light and sound.
