The human factors involved in manned space flight, according to Strughold, the province of space medicine. Space medicine per se is, he believes, "a logical extension of aviation medicine inasmuch as there are many interrelations between the two."1 Since space medicine deals with the problems involved in astronautics, it is "by and large, identical with bioastronautics…" Thus, space medicine includes the study of conditions on other celestial bodies and their effect on explorers in terms of human physiology. It overlaps astrobiology, the study of the possibilities of indigenous life on other celestial bodies. The term "planetary ecology" covers both the medical and biological aspects.
Space medicine belongs in the category of industrial medicine, specifically environmental medicine. It involves the biophysics of the environment of space—the ecology of space; gravity and motions in Space flight; classification and medical characterization of the various kinds of space operations; the space cabin; weightlessness as the outstanding novel environmental factor; and the medical aspects of the prospects and limitations of space flight.2 In the area between space medicine and traditional aviation medicine, there are certain overlappings, such as the tolerability of high g-forces and rapid decompression.
Since the physiological effects of the space environment are the major concern of Space medicine, efforts have been made to define the elusive term "space" as a physiological entity. In the early 1950's Strughold and his coworkers suggested that the atmosphere ceases and space begins at different altitudes for different physiological functions. This altitude was designated the region of space equivalence, or the functional border of space.3 While it is not the purpose of the present study to discuss the physiological problems facing maid in space flight—which have been ably discussed elsewhere—they should be kept in mind by the reader, because in 1958 and in the year following the answers had not yet been found. Only actual flight into space could answer these questions.
The problems of biomedical support for the short-term Project Mercury flights were relatively simple, it was believed, and could be solved through existing technology which would provide adequate life systems for man's survival in orbital flight. This orbital path would lie below the Van Allen belt, so that radiation would pose no great problem. There were, however, other problems which would be involved both in the relatively limited Mercury mission and in extended missions.
The first of these was the problem of acceleration and weightlessness. On the basis of extrapolation from data on humans flown in Keplerian trajectories, animal experiments utilizing V-2 and Aerobee rockets, water-immersion experiments, and experiments involving sensory deprivation, it was anticipated that the principal difficulties would be in the central nervous system and organs of position sense. The chief consequences were believed to be disorientation, hallucinations, and psychological adjustment failures, of which disorientation was the most difficult to assess.4 A second major problem was that of combined stresses including noise, launch, and reentry tolerance. The third was the problem of toxic hazards in the spacecraft. Fourth was the danger from ambient space radiations.5
These, then, were problems involving basic biological research and development, testing, and validation, as Project Mercury got underway.
1. Hubertus Strughold, "Space Medicine," ch. 31 In Harry G. Armstrong, Aerospace Medicine (Baltimore: Williams & Wilkins, 151), p. 595.
2. Ibid., p. 596.
3. H. Strughold, H. Haber, K. Buettner, and F. Haber, "Where Does Space Begin?: Functional Concept of the Boundaries Between Atmosphere and Space," J. Aviation Med., vol. 22, no. 5, Oct. 1951, pp. 342-349, 357; H. Strughold, "Atmospheric Space Equivalent," J. Aviation Med., vol. 2.,, no. 4, Aug. 1954, pp. 420-424.
4. The literature in the field is voluminous. For the Project Mercury account, see J. P. Henry, W. S. Augerson, et al., "Effects of Weightlessness in Ballistic and Orbital Flight," J. Aerospace Med., vol. 33, no. 9. Sept. 1962, pp. 1056-1068. See also, for example, (1) E. R. Ballinger, "Human Experiments in Subgravity and Prolonged Acceleration," J. Aviation Med., vol. 23, no 4, Aug. 1952, pp. 319-321, 372; (2) S. Bondurant, W. G. Blanchard, N. P. Clarke, and F. Moore, "Effect of Water Immersion on Human Tolerance to Forward and Backward Acceleration," J. Aviation Med., vol. 29, no. 12. Dec. 1958, pp. 872-878; (3) E. L. Brown, "Zero Gravity Experiments," abstracted in, J. Aviation Med., vol. 30, no. 3, Mar, 1959, p. 177, under title "Research on Human Performance During Zero Gravity"; (4) P. A. Campbell and S. J. Gerathewohl, "The Present Status of the Problems of Weightlessness," Texas State, J. Med., vol. 55, no. 4, Apr. 1959, pp. 267-274; (5) B. Clark and A. Graybiel, "Human Performance During Adaptation to Stress In the Pensacola Slow Rotation Room," Aerospace Med., vol. 32, no. 2, Feb. 1961, pp. 93-106; (6) O. Gauer and H. Haber, "Man Under Gravity-Free Condition," in German Aviation Medicine—World War II, vol. I, ch. VI (Washington, D.C.: 1950) pp. 641-644; (7) S. J. Gerathewohl and H. D. Stallings, Experiments During Weightlessness: A Study of the Oculo-Agrsvic Illusion," J. Aviation Med., vol. 29, no. 7, July 1958, pp. 504-516; (8) D. E. Graveline and B. Balke, "The Physiologic Effects of Hypodynamics Induced by Water Immersion," USAF SAM Rep. No. 60-88. Sept. 1960; (9) A. Graybiel, F. E. Guedy, W. Johnson, and R. Kennedy, "Adaptation to Bizarre Stimulation of the Semi-Circular Canals as Indicated by the Oculagyral Illusion," Rep. No. 53, USN School of Aviation Medicine, July 27, 1960; (10) H. J. Von Beckh, "Experiments With Animals and Human Subjects Under Sub and Zero-Gravity Conditions During the Dive and Parabolic Flight," J. Aviation. Med., vol. 25, no. 3, June 1954, pp. 235-241; (11) J. E. Ward, W. R. Hawkins, and H. D. Stallings, "Physiologic Responses to Subgravity—I Mechanics of Nourishment and Deglutition of Solids and Liquids," Aerospace Med., vol. 30, no. 6, June 1959, 11p. 151-154; "Physiologic Responses to Subgravity—II. Initiation of Micturation," Acro-space Med., vol. 30, no. S, Aug. 1959, pp. 572-575; and (12) G. D. Whedon, .J. E. Deitrick. and E. Shorr, "Modification of the Effects of Immobilization Upon Metabolic and Physiological Functions of Normal Men by Use of an Oscillating Bed," Am. J. Med., vol. 6, no. 6, June 1949, pp. 684-711.
5. For discussion of these latter three topics, see, for example, Harry G. Armstrong. Aerospace Medicine (Baltimore: The Williams & Wilkins Co., 1961), particularly ch. I, Armstrong, "The Atmosphere"; ch. 13, Richard W. Bancroft, Medical Aspects of Pressurized Equipment"; ch. 15, Armstrong, "Vertigo and Related States"; ch. 16, Ralph L. Christy, "Effects of Radial and Angular Accelerations"; ch. 17, John P. Stapp, "Effects of Linear Acceleration": ch. 18, Horace O. Parrock, "Effects of Acoustic Energy"; ch. 19, Paul Webb. "Temperature Stresses"; ch. 22, Lawrence E. Lamb, "Cardiovascular Considerations"; and ch. 25, John E. Byson, "Toxicology in Aviation." See also Otis O. Benson, Jr., and Hubertus Strughold, eds., Physics and Medicine of the Atmosphere and Space (New York: John Wiley & Sons, Inc., 1960); Ursula T. Slager, Space Medicine (New York: Prentice-Hall, 152); and M. P. Iansherg, A Primer of Space Medicine (Amsterdam: Elsevier Publishing Co., 1960). See also Charles H. Roadman, "Aerospace Medical Support of Manned Space Flight," USAF Medical Services Digest, vol. XIII, no. 9, Sept. 1962, pp. 2-9, 25.