The Influence Of The Dynamic Environment On Man In Space Flight
Possible stresses in space flight include a broad mechanical spectrum. In this paper most of the emphasis will be placed on transient and prolonged linear accelerations though it is recognized that vibrations and rotations could become important.
In preparing manto be exposed to the prolonged accelerations of space flight it was realized that his body orientation in the force field was of great importance if he was to maintain his capacity for observing and ability to perform tasks. By arranging for these forces to be applied across his body (transversely), instead of along the length of his body, circulatory difficulties can be reduced and his tolerance increased. However, at the higher accelerations tolerable in the transverse position other difficulties appear most by involving respiration. Not only is it more difficult to inspire air, but, because of a displacement of the blood perfusing the lungs, there is imperfect exchange between pulmonary air and blood. This physiological pulmonary shunt results in a reduction in the oxygen content of arterial blood. Furthermore, the inertial forces due to acceleration may cause congestion of some portions of the lungs with overdilation of other portions with danger of atelectasis and mediastinal emphysema.
It is pointed out that neither positive pressure respiration, the breathing of high oxygen pressures nor immersion in water can completely protect against these changes.
The status of our knowledge of the tolerance of man to abrupt transient accelerations is reviewed with some discussion of the difficulties of investigation in this field.
Though the orbital flights made to date have tended to reassure us that man can tolerate the dynamic environment of space flight, there are possible deviations from normal flight plans which could involve dangerous forces. Some of these are described.
Unable to display preview. Download preview PDF.
- 1.B. Aldman, Biodynamic Studies on Impact Protection. Acta Physiol. Scand. 56, Suppl. 192 (1962).Google Scholar
- 4.S. Bondurant and G. Transverse, Prolonged Forward, Backward and Lateral Acceleration. Chapt. 16 in: Gravitational Stress in Aerospace Medicine. Edited by R. H. Gauer and G. D. Zuidema. Boston,Mass.: Little, Brown and Co., 1961.Google Scholar
- 5.N. S. Cherniak, A. S. Hyde, J. F. Watson, and F. W. Zeckman, Some Aspects of Respiratory Physiology with Forward Acceleration. Aerospace Med. 32, 113 (1961).Google Scholar
- 6.C. C. Clark and R. F. Gray, A Discussion of Restraint and Protection of the Human Experiencing the Smooth and Oscillating Acceleration of Proposed Space Vehicles. Report No. NADC-MA 5914, US Naval Air Development Center, Honnsville, Pa.Google Scholar
- 7.C. C. Clark, J. D. Hardy, and R. T. Crosbie, A Proposed Physiological Acceleration Terminology with a Historical Review. In: Human Acceleration Studies, National Academy of Sciences-National Research Council Publication 913, 1961.Google Scholar
- 8.A. M. Eiband, Human Tolerance to Rapidly Applied Accelerations. A Summary of the Literature. NASA Memo 5-19-59E, June 1959.Google Scholar
- 9.E. J. Hershgold, Roentgenographic Study of Human Subjects During Transverse Accelerations. Aerospace Med. 36, 213 (1960).Google Scholar
- 10.E. J. Hershgold and S. H. Steiner, Cardiovascular Changes During Acceleration Stress in Dogs. J. Appl. Physiol. 15, 1065 (1960).Google Scholar
- 11.D. E. Langdon and G. E. Reynolds, Post Flight Respiratory Symptoms Associated with 100per Cent Oxygen and G-Forces. Aerospace Med. 32, 713 (1961).Google Scholar
- 12.E. F. Lindberg, H.W. Marshall, W. F. Sutterer, T. F. McGuire, and E. Rood, Studies of Cardiac Output and Circulatory Pressures in Human Beings During Forward Acceleration. Aerospace Med. 33, 81 (1962).Google Scholar
- 13.E. F. Lindberg, W. F. Sutterer, H. W. Marshall, R. N. Headley, and E. W. Wood, Measurement of Cardiac Output During Headward Acceleration Using the Dye Dilution Technique. Aerospace Med. 31, 817 (1960).Google Scholar
- 14.J. P. Meehan, Renal Responses to Positive Acceleration. Wright Air Development Division Technical Report 60-637, Sept. 1960.Google Scholar
- 15.A. C. Nolan, H. W. Marshall, L. Cronin and E. H. Wood, Decreases in Arterial Oxygen Saturation as an Indicator of Cardio-pulmonary Stress During Forward (+Gx) Acceleration. Aerospace Med. 33, 347 (1962)Google Scholar
- 16.Proceedings of a Conference on Results of the First U.S. Manned Suborbital Flight, NASA, Nat. Inst. Health and Nat. Acad. Sci, June 6, 1961.Google Scholar
- 17.Results of the First U. S. Manned Orbital Space Flight Feb. 20, 1962. National Aeronautic and Space Administration, Manned Spacecraft Center.Google Scholar
- 18.S. H. Steiner, G. C. E. Mueller, and J. L. Taylor, Hemodynamic Changes During Forward Acceleration. Aerospace Med. 31, 907 (1960).Google Scholar
- 19.S. H. Steiner and G. C. E. Mueller, Pulmonary Arterial Shunting in Man During Forward Acceleration. J. Appl. Physiol. 16, 1081 (1961).Google Scholar
- 20.A. M. Stoll and J.D. Moseley, Physiologic and Pathologic Effects in Chimpanzees During Prolonged Exposure to 40 Transverse G. Aerospace Med. 29, 575 (1958).Google Scholar
- 21.J. J. Swearingen, E. G. McFadden, J. P. Garver, and J. G. Blethrow, Human Voluntary Tolerance to Vertical Impact. Aerospace Med. 31, 989 (1960).Google Scholar
- 22.J. F. Watson and N. S. Cherniak, The Effect of Positive Pressure Breathing on the Respiratory Mechanics and Tolerance to Forward Acceleration. Proceedings of the 5th European Congress of Aviation Medicine, 1960.Google Scholar
- 23.J. F. Watson and R. M. Rapp, Effect of Forward Acceleration on Renal Function. J. Appl. Physiol. 17, 413 (1962).Google Scholar
- 24.P. Bergeret, Editor-Bio-Assey Techniques for Human Centrifuges and Physiological Effects. London, New York, Paris: Pergamon Press, 1961.Google Scholar
- 25.O. H. Gauer and G. D. Zuidema, Gravitational Stress in Aerospacè Medicine. Boston, Mass.: Little, Brown and Co., 1961.Google Scholar
- 26.H.E. von Gierke and E. P. Hiatt, Biodynamics of Space Flight. Chapt. VII in: Progress in the Astronautical Sciences, Vol. 1. Edited by S. F. Singer. Amsterdam: North Holland Publishing Co., 1962.Google Scholar