Retired Astronaut Scott Kelly Reveals Physical Setbacks From Time in Space

Kelly says his year in space took a physical toll.

But despite the physical setbacks Kelly describes, the veteran Navy pilot will also detail in the book his faith in space exploration and his desire to see both government-backed and private space travel, according to Knopf.

Kelly shared his enthusiasm about the book on Twitter, saying he was "excited to share this incredible #YearInSpace experience."