The development of specifications and negotiation of the contract was the end result of NACA research and development which had been in progress since early 1952, with close cooperation between military and industrial specialists. In June of that year, a small working group had been established "to analyze available information on Space flight, and to arrive at, a concept of a suitable manned test vehicle which could be, constructed within two years."2
As a result of the recommendation by the NACA Committee on Aerodynamics that the problems of manned and unmanned flight at altitudes above 15 miles be considered, the Langley Aeronautical Laboratory began preliminary studies. Several problem areas were immediately identified, including those of aerodynamic heating and the achievement of stability and control at very high altitudes and speeds. For the next 4 years, personnel at the NACA Langley and Ames Laboratories were engaged in research on aerodynamic characteristics of reentry configurations. They also contributed to the military missile program (which is not pertinent to the present discussion).
As a result of studies conducted the previous year, Maxime Faget, later the Assistant Director for Engineering and Development at the Manned Spacecraft Center, and his associates at the Langley Aeronautical Laboratory prepared a ballistic shape in November 1957 for a manned satellite development project. In January 1958 he and Paul E. Purser, later Special Assistant to the Director, MSC, conceived a solid-fuel design for the launch vehicle to be used in the research and development phase of a manned satellite project. Designated "Little Joe," this launch vehicle was used extensively in the early testing stages of Project Mercury. A report entitled "Preliminary studies of Manned Satellites—Wingless Configuration, Non-Lifting," completed by Faget, Benjamine Garland, and James J. Buglia in March 1958, was later to become the working paper for the Project Mercury development program.3
In the various research projects preceding Project Mercury, considerable attention had been given to the problems of acceleration and reentry forces of manned space flight. Indeed, these may be said to have been the last remaining major obstacles to manned space flight.
Both the German Air Force prior to World War II and the U.S. Army Air Forces had considered various techniques such as traveling in a prone position.4 As early as 1932, 11. von Diringshofen pointed out that man's "g" tolerance would be markedly enhanced if the force were directed perpendicular to the axis of the large (great) blood vessels, as in the prone or supine position. In 1936, L. Buhrlen, from considerations based upon centrifuge experiments on supine human subjects, recommended the use of a seat which at 4 to 5 g automatically tilted backward to the horizontal. H. Wiesebofer in 1939, presumably motivated by these earlier suggestions of a tilting seat, actually flight tested a g-actuated tilting seat in a Heinkel-50 two-seated airplane, in which five passengers withstood 7g for 15 seconds without visual symptoms. In this installation, however, no flight tests were made in which the pilot utilized the tilting seat. In the Compendium of Aviation Medicine. S. Ruff and H. Strughold (1939) alluded to the work of Wiesehofer and similar observations, declaring that the g-actuated tilting seat had been shown to be "entirely practical."
Several American investigators later considered and designed g-actuated tilting seats for pilots of highly maneuverable aircraft. F. P. Dillon in 1942 patented a hydraulic g-actuated seat, and J. J. Ryan and B. H. T. Lindquist in 1943 described a spring-controlled g-actuated seat, not unlike the one von Diringshofen had described a decade and a half earlier.
W. G. Clark, J. P. Henry, D. R. Drury, and P. O. Greeley at the University of Southern California in the early 1940's were able to relate the positioning of the body and limbs quantitatively about the, g-vector to the change in human g-tolerance. In the same period, E. H. Wood, C. F. Code, and E. J. Baldes studied the Ryan-Lindquist seat in detail for g protection provided when the seat was oriented at 45° from the horizontal.
In 1948, H. T. E. Hertzberg of the USAF Aero Medical Laboratory, Ohio, fabricated and tested on the centrifuge a "prone position bed" on which the human subject was easily able to withstand 12g. As an outgrowth of this and the earlier work of others, in 1949 he constructed, and in early 1950 tested, a net seat in which the supporting material was nylon raschel net which in the unloaded condition hung slack on the frame. This "slack net" was tested and was found to be extremely comfortable. It also was believed to provide lateral support to the postero-lateral aspects of the trunk.
In the period 1957-1960, J. I. R. Bowring, RAF, on duty at Wright-Patterson Air Force Base, Ohio, also constructed a net seat, based largely on the work of Hertzberg. His design departed from that of Hertzberg mainly in that he used as a support a raschel net material stretched taut over the seat frame. This supine seat did not display the same degree of subjective comfort as the slack net seat. It was also demonstrated that the taut net seat was unable to attenuate certain vibrational resonances of interest to human occupants.
Faget and his associates in April 1958 suggested the idea of using a contour couch to withstand the high g-loads in Mercury flights.5 In May 1958, fabrication of test-model contour couches was started in Langley shops. The couch proved to be feasible on July 30 when a subject withstood a 20-g load on the Navy centrifuge at Johnsville, Pa.6
Except in this one area, however, engineers and bioastronautics experts had yet to define the life-support criteria for manned space flight. Insofar as possible they would draw upon Air Force and Navy experience in the development of hardware for high-speed, high-altitude flight.
Three major factors had to be considered in the planning for the human operation of a spacecraft: (1) the stresses the astronaut would encounter, (2) the functions he would perform, and (3) the phases of the mission in which these factors would be encountered.7
Four categories of stresses could be expected: (1) Those caused by motions or forces, or their absence; (2) those caused by the space environment itself; (3) those caused by the spacecraft environment; and (4) those caused by the mental and physical activities required of the astronaut. Stresses caused by motions or forces included acceleration, weightlessness, noise and vibration, and oscillatory motions. Those caused by the space environment itself included radiation, micrometeoroid impact, and illumination. Those caused by the spacecraft environment. included the atmosphere of the spacecraft, isolation, nutrition and waste factor, and other comfort factors. Finally, those stresses caused by the mental and physical activities of the astronaut included orientation ability, task complexity, and psychological factors.
Normally these stresses did not occur simultaneously and they were critical only during specific phases of the mission. According to Charles W. Mathews, Chief, Spacecraft Research Division, NASA Manned Spacecraft Center, in an address before the International Space Science Symposium: "We are interested not only in whether the astronaut can complete the mission without. Undue stress, but also whether he can perform certain critical functions at the same time."8 During the flight mission, critical stresses would occur at different points in time as different phases of the mission were in progress including powered flight, free flight, space maneuvers, operations in atmosphere, terminal flight, and surface operations.
The Mercury program—which was an experiment to test the ability of a man and machine to perform in a controlled but not completely known environment—was to start with a series of design experiments for which there were few criteria. Design philosophy based upon experiments changed as the program progressed—for example, the shape of the spacecraft itself.9
Because man's capabilities to perform in space were unknown, early design philosophy was based upon automatic systems to perform the critical functions, with man riding along as a passenger and observer. Later this philosophy changed as it was increasingly demonstrated that man could effectively operate the manual controls and thereby provide a redundancy in case the primary systems failed.10
Design of a life-support system for Project Mercury could be accomplished by engineering and technology, but, according to Christopher Kraft, Jr., of the NASA Manned Spacecraft Center, "we cannot redesign the man who must perform in space."11 Biomedical experiments would therefore have to answer one question: Could a man adapt to an environment which violates most of the laws under which his earth-oriented body normally operates?
Mercury objectives were to be in two areas: (1) scientific, and (2) engineering and technological. The scientific concern, involving all disciplines of the life sciences, was to determine man's capabilities in a space environment and in those environments associated with entering and returning from space. The engineering and technological problem was to place a manned vehicle safely into flight and effect a safe recovery of both man and vehicle from orbit. This total scientific and engineering-technological mission would require a life-support system that could sustain the astronaut throughout his total mission time including launch, orbit, and recovery. Dr. Stanley C. White and his deputy, Richard S. Johnston, an engineer, were to provide the focal point within the STG Life Systems Division for integrating the biomedical aspects of the life-support system within the total configuration.
2. Project Mercury, NASA Fact Sheet 195, Manned Spacecraft Center, July 1963. pp 2-3.
3. Ibid., P. 3.
4. The literature in the field is extensive. See for example: (1) W. G. Clark, "Effect of Changes in the Position of the Body and Extremities on Seated Man's Ability to Withstand Positive Acceleration," Unpublished National Research Council Monograph, 1946; (2) W. G. Clark, "Tolerance of Transverse Acceleration with Especial Reference to the Prone Position," Unpublisbed NRC Monograph, 1946; (3) Personal communication, Walter R. Sullivan, Jr., with H. T. E. Hertzberg, C. E. Clauser, and F. W. Berner, Aeromedical Laboratory, Wright-Patterson AFB, Ohio; J. P. Henry, M.D., Dept. Pbyslology, ITSC; William G. Clark, Veterans Administration Hospital. Sepulvada. Calif.; E. J. Baides, Ph.D., Department of Defense; Mr. Harvey Holder, Engineering Directorate of Defense and Transport System; Mr. Richard Peterson, Research and Technology Division, Wright-Patterson AFB, May 1965.
5. Project Mercury, NASA Fact Sheet 195, Manned Spacecraft Center, July 1963, p. 3.
7. Charles E. Mathews, "United States Experience on the Utilization of Man’s Capabilities In a Space Environment," in R. B. Livingston, A. A. Imshenetsky, and G. A. Derbyshire, eds., Life Sciences and Space Research (New York: John Wiley & Sons, Inc., 1963).
8. Ibid., p. 144.
9. Christopher C. Kraft, Jr., "A Review of Knowledge Acquired From the First Manned Satellite Program," NASA Fact Sheet 206, Manned Spacecraft Center, circa Aug. 1963.
10. Edward R. Jones, "Man's Integration into the Mercury Capsule," presented at the 14th Annual Meeting, American Rocket Soc. Washington, D.C. Nov. 16-19, 1959. See also Robert B. Voas, "Project Mercury: The Role of the Astronaut in Project Mercury Space Flights," presented at the VPI-NSF-NASA Conference on Physics of the Solar System and Reentry Dynamics, Blacksburg, Va., Aug. 10, 1961.
11. Kraft, op. cit.