When it comes down to it, there are only two ways to send crewed missions to exoplanets. The first is to develop advanced propulsion systems that can achieve relativistic speeds (a fraction of the speed of light). The second involves building spacecraft that can sustain crews for generations – aka. a Generation Ship (or Worldship).
https://www.sciencealert.com/the-radical-plan-to-build-a-spaceship-to-carry-humans-for-generations
