In the 1960s, humans took their first steps away from Earth, and for a time our possibilities in space seemed endless. But in a time of austerity and in the wake of high-profile disasters like Challenger, that dream seems to have ended. In early 2011, Margaret Lazarus Dean traveled to Cape Canaveral for NASA's last three space shuttle launches in order to bear witness to the end of an era. In her new book "Leaving Orbit: Notes from the Last Days of American Spaceflight" Dean serves as our guide to Florida's Space Coast and to the history of NASA.