Book excerpt: Just what does it take to be a stratonaut, soaring to higher and higher altitudes of Earth's atmosphere? Brave men and women have reached extreme heights in balloons, aircraft and rocket ships over the past two centuries, from the first untethered balloon flight to the first flights in the newly defined stratosphere, through to the present flights that continue to set new records. This book defines the altitudes related to the stratosphere, how it changes with latitude and the effects on ascending aviators. Also described is how over time technology enabled aircraft and balloons to achieve higher altitudes. The book shows the clear influence of the military on designs that initially focused on speed and maneuverability, but only later on reaching new altitudes. The early flights into the troposphere and eventually the mid to upper reaches of the stratosphere are chronicled, with great emphasis on flight operations. This includes decompression, bailouts, inertia coupling, ejections, catastrophic disintegration, crashes and deaths. Although the book highlights major altitude attempts and records, it also focuses on the life-threatening problems confronting the would-be stratonaut and the causes of many of their deaths. In doing so, it tries to define just what it takes to be a stratonaut.