In November 1948, Armstrong organized at Randolph a panel discussion on the "Aeromedical Problems of Space Travel." Featuring papers by Strughold and Heinz Haber and commentary by six well-known scientists from universities and the military, the symposium perhaps marked the beginning of formal, academic inquiry into the medical hazards of extra-atmospheric flight. Before this epochal gathering ended, Strughold had resolved the contradiction inherent in the title of the symposium by emphatically using the term "space medicine."4
The following February, Armstrong set up the world's first Department of Space Medicine, headed by Strughold and including the Habers and Konrad Buettner.5 In November 1951, at San Antonio, the School of Aviation Medicine and the privately financed Lovelace Foundation for Medical Research at Albuquerque, New Mexico, sponsored a symposium discreetly entitled "Physics and Medicine of the Upper Atmosphere." It was still not respectable to speak plainly of space flight within the Air Force, which only that year had cautiously reactivated its intercontinental ballistic missile project and remained sensitive to "Buck Rogers" epithets from members of Congress and the taxpaying public. A good portion of the material presented by the 44 speakers at the 1951 symposium, however, covered the nature of space, the mechanics of space flight, and the medical difficulties of sending a man beyond the sensible and breathable atmosphere.6
An important bridge from aviation medicine to space medicine was this chart by Hubertus Strughold in 1951. It related altitudes at which human functional borders occur with the altitudes at which the various physical characteristics of space occur.
It was at this meeting that Strughold, later to acquire a reputation as the "father of space medicine," put forth what is perhaps his most notable contribution - the concept of "aeropause," a region of "space-equivalent conditions" or  "atmospheric space equivalence." Strughold pointed out that while many astronomers, astrophysicists, and meteorologists set the boundary between the atmosphere and space at about 600 miles from Earth, the biological conditions of space begin much lower, at about 50,000 feet. Anoxia is encountered at 50,000 feet, the boiling point of body fluids at 63,000 feet, the necessity for carrying all respiratory oxygen within a manned compartment at 80,000 feet, meteoroids at 75 miles, and the darkness of the space "void" at 100 miles. Above 100 miles the atmosphere is imperceptible to the flyer. "What we call upper atmosphere in the physical sense," said Strughold, "must be considered - in terms of biology - as space in its total form." Hence manned ballistic or orbital flight at an altitude of 100 miles would be, for all practical purposes, space flight.7
The rocket-powered research airplanes of the postwar years, beginning with the X-1, the first manned vehicle to surpass the speed of sound, took American test pilots well into the region of space equivalence. On August 26, 1954, when Major Arthur Murray of the Air Force pushed the Bell X-1A to an altitude of  90,000 feet, he was above 90 percent of the sensible atmosphere. Two years later, in the more powerful Bell X-2, Air Force Captain Iven Kincheloe climbed to 126,000 feet, "a space-equivalent flight to a very high degree."8 The X-15, still on the drawing boards in the mid-fifties, was being designed to rocket its pilot to an altitude of 50 miles at nearly seven times the speed of sound. And human-factors research in the X-15 project, involving the development and testing of a new full-pressure flying suit, centrifuge conditioning to high acceleration forces, and telemetering a wide range of physiological data in flight, would contribute substantially to medical planning for space travel.9
2 For the German work in aeromedicine during the 1930s and early 1940s, see U.S. Air Force, German Aviation Medicine, World War II (2 vols., Washington, 1950).
3 Harry G. Armstrong, Principles and Practices of Aviation Medicine (3 ed., Baltimore, 1952). Armstrong later became a major general.
4 Harry G. Armstrong, Heinz Haber, and Hubertus Strughold, "Aero Medical Problems of Space Travel, Panel Meeting, School of Aviation Medicine," Journal of Aviation Medicine, XIX (Dec. 1949), 383-417; Hubertus Strughold, interview, San Antonio, April 24, 1964. People interested in the physiology and psychology of extra-atmospheric flight have devised a number of terms to describe their field of investigation - biomedicine, space biology, astrobiology, bioastronautics, aerospace medicine. The most suitable single term seems to be that used by Strughold, "space medicine." It is used throughout this work except where more precise terminology, such as "biodynamics," appears appropriate.
5 Shirley Thomas, Men of Space (6 vols., Philadelphia, 1960-1963), IV, 234-250; USAF Air Training Command, History of the United States Air Force, Pamphlet 190-1, Randolph Air Force Base, Tex., 1961, 19; Strughold interview. Siegfried J. Gerathewohl, a psychologist, and Hans-Georg Clamann, a physiologist, remained with the School of Aviation Medicine but did not become members of the Department of Space Medicine.
6 Clayton S. White and Otis O. Benson, eds., Physics and Medicine of the Upper Atmosphere: A Study of the Aeropause (Albuquerque, 1952).
7 Hubertus Strughold, "Basic Environmental Problems Relating Man and the Highest Regions of the Atmosphere as Seen by the Biologist," ibid., 32. On the concept of space equivalence see also Strughold, Heinz Haber, Konrad Buettner, and Fritz Haber, "Where Does Space Begin? Functional Concept of the Boundaries between the Atmosphere and Space," Journal of Aviation Medicine, XXII (Oct., 1951), 342-357; Strughold, "Atmospheric Space Equivalence," Journal of Aviation Medicine, XXV (Aug., 1954), 420-424; Strughold, "The Medical Problems of Space Flight," International Record of Medicine, CLXVIII (1955), 570-575; and Strughold, "A Simple Classification of the Present and Future Stages of Manned Flight," Journal of Aviation Medicine, XXVII (Aug., 1956), 328-331.
8 "Thirty-Five Years of Winged Rocket Flight," Thiokol Magazine, II (1963), 10; Hubertus Strughold, "Introduction," to Morton Alperin, M. Stern, and H. Wooster, eds., Vistas in Astronautics: First Annual Astronautics Symposium (London, 1958), 283.
9 See Burt Rowen, "Human Factors Support of the X-15 Program," in Kenneth F. Gantz, ed., Man in Space: The United States Air Force Program for Developing the Spacecraft Crews (New York, 1959), 216-221; Stanley C. White, "Progress in Space Medicine," paper, Second World and Fourth European Aviation and Space Medicine Congress, Rome, Oct. 27-31, 1959; and Richard E. Day, "Training Aspects of the X-15 Program," in The Training of Astronauts (Washington, 1961), 5-14.