After World War II, military planes were getting faster, and the pilots who flew them were dying at an alarming rate. Dr. John Stapp, an Air Force researcher, was tasked with discovering how many G-forces the human body could withstand. To do so, Stapp became a human guinea pig, strapping himself aboard a rocket sled and blasting across the desert at record-breaking speeds. By putting his own life on the line, Col. Stapp's research ultimately saved millions of lives.