All star flights are one-way voyages.
The stars that beckon to us at night are mind-numbingly distant. Even traveling at nearly the speed of light, it takes decades, centuries to reach just the nearest of them. Then, when the star rovers come back home to Earth, more decades, centuries will have elapsed. The returning travelers will be strangers on the world of their birth.
Some humans accepted that inescapable fate. Some men and women willingly boarded the starships and journeyed into the unknown, driven by personal demons that outweighed all other consequences. Some were among humanity’s best and brightest. Some were fleeing into the future willingly. The psychotechnicians who examined and tested them realized that in some cases, the difference between genius and madness was too slim to separate.