High Quality Content by WIKIPEDIA articles! The Armstrong limit, often called Armstrong`s line, is the altitude that produces an atmospheric pressure so low (0.0618 atmosphere) that water boils at the normal temperature of the human body: 37 °C (98.6 °F). It is named after Harry George Armstrong, who founded the U.S. Air Force’s Department of Space Medicine in 1947 at Randolph Field, Texas. Armstrong was first to recognize that the phenomenon represented an absolute altitude beyond which humans could not survive in an unpressurized environment. The altitude is variously reported as being between 62,000–63,500 feet (18,900–19,350 meters or about 12 miles).