Back in February 1959, Maxime Faget and Stanley White became convinced that the so-called "pressure" suits being used by Air Force and Navy test pilots were rather "high-pressure" and partially anti-g flying suits. Ever since 1947 the Air Force and the Navy, by mutual agreement, had specialized in developing partial-pressure and full-pressure flying suits, respectively, but a decade later neither type was quite satisfactory for the newest definition of extreme altitude protection. Such suits would require extensive modifications, particularly in their air circulation systems, to meet the needs of the Mercury space pilots. The first suit conference on January 29, 1959, attended by more than 40 experts in the art of tailoring for men engaged in high-altitude flying, had recommended an extensive evaluation program.14 Through the spring three primary competitors - the David Clark Company of Worcester, Massachusetts (a prime supplier for Air Force pressure suits), the International Latex Corporation of Dover, Delaware (a bidder on a number of government contracts involving rubberized material), and the B. F. Goodrich Company of Akron, Ohio (suppliers of most of the pressure suits used by the Navy) - competed to provide by the first of June their best products for a series of evaluation tests.
 NASA had requested the Air Force Aeromedical Laboratory at Wright Air Development Center and the Navy Air Crew Equipment Laboratory in Philadelphia to plan and perform evaluations of the different test suits before mid-July. The Clark and Goodrich suits ranked highest in both evaluation programs, but predictably the Air Force favored the Clark suit and the Navy the Goodrich suit. After an evaluation conference on July 15 at Langley, the chairman, Richard Johnston, informed all parties of STG's decision to work with both the Clark and the Goodrich companies for several more months to allow further concurrent development and evaluation of various combinations of suits and ventilation systems.15 By the end of August, William Augerson and Lee N. McMillion of STG recommended that "the suit should not be expected to cope with all the deficiencies of the Mercury capsule." The close interface between pressure suit and environmental control system caused enough problems to delay the formulation of suit specifications until October, but Goodrich was awarded the prime contract for the Mercury space suit on July 22, 1959.16
One of the most senior employees of the Goodrich Company was Russell M. Colley. In 1933, Wiley Post returned from the first solo flight around the world and wanted some kind of rubber suit that would enable him to fly his famous aircraft Winnie Mae above the record 47,000-foot altitude. Colley had designed an aluminum helmet resembling those used by marine divers and had stitched together on his wife's sewing machine the first crude space suit. The next year Colley and his company had designed and developed a more flexible flying suit for Wiley Post, with an off-center face plate to accommodate Post's one-eyed vision. In 1952, Colley had designed and helped develop swivel joints of air-tight bearings and fluted fittings for pressure suits fabricated by Goodrich for the Naval Bureau of Aeronautics. In 1959, Colley, along with Carl F. Effler, D. Ewing, and other Goodrich employees, was instrumental in modifying the famous Navy Mark IV pressure suit for NASA's needs in orbital flight.
Although the decision to let the capsule itself provide primary protection minimized the difference between corseted, pressurized g suits and a "space suit" for Project Mercury, the redundant suit environmental control system required complicated modifications and continual refittings.
The Task Group had discovered during 1959 that each Mercury capsule would have to be specially tailored to its own mission objectives. Pressure suits also were designed individually according to use - some for training, others for evaluation and development. Thirteen operational research suits first were ordered to fit astronauts Schirra and Glenn, their flight surgeon Douglas, the twins Gilbert and Warren J. North, at McDonnell and NASA Headquarters, respectively, and other astronauts and engineers to be specified later. A second order of eight suits supposedly would represent the final configuration and provide adequate protection for all flight conditions in the Mercury program.
The three major parts of the space suit - the torso coveralls, the helmet, and the gloves - were fabricated by techniques and procedures similar to those already  in use in the manufacture of full-pressure flying suits. But the air system operation was unusual:
The Mercury headpiece is a single cavity design with suit ventilation air exiting through the exhaust valve located in the right cheek area. This system is known as the "closed" or "single gas" system and utilized one air source for ventilation as well as breathing. This concept, which is desirable in space missions, permits simplicity of design and minimum weight of the ventilation and respiration equipment.17According to Lee McMillion of STG's Life Systems Branch, the Big Joe reentry heating test in September 1959 allowed the developers of the pressure suit to remove much of the insulation previously thought necessary. This improved somewhat the mobility of the astronaut under full pressurization. By the end of the year McMillion, Colley, Schirra, and Glenn A. Shewmake, STG's "tailor," chose to modify the suit to facilitate mobility in the capsule rather than repattern for a more generally mobile suit. Schirra had felt many pressure points and was severely constricted in recent tests. His discomfort was traced to the design conservatism that had accepted the g suit and oxygen mask concepts used for the Navy Mark IV and Air Force X-15 flying suits. Furthermore, each time these prototype space suits were pressurized and worn, they stretched out of shape.18
Throughout the spring of 1960, fittings and tests with new textiles, different materials, and other human models continued until they finally solved the stretching problem. In mid-March a committee of eight members from STG, McDonnell, the Navy, and Goodrich decided on the final design features for the Mercury space suits. All kinds of minor troubles with zippers, the visor, the segmented shoulder, lacings, straps, snaps, seams, valves, underwear, gloves, microphones, and neck dams continued. But after a "gripe session" in mid-May 1960, the astronauts and their tailors essentially agreed on what the well-dressed man should wear into space.19
Environmental Control System.
During an orbital flight, certain physiological limitations were expected to establish the requirements for matching man and machine in one smoothly functioning system.20 In the area of noise and vibration, for example, research during the 1950s had led to the conclusion that 140 decibels, in the broad spectrum between 100 and 12,000 cycles per second, was the most that man could stand for durations of four or five seconds. Acceleration tolerances were rising, thanks to knowledge gained by centrifuge and rocket sled tests, but above 6 g pilots could breathe only by forcing abdominal constriction and could move effectively only their hands and fingers. An oxygen pressure inside the lungs corresponding to that of 100 millimeters of fluid mercury was judged necessary to preclude any symptom of hypoxia. To guard against the danger of "bends" (caisson disease or dysbarism), the cabin pressure should not be more than twice the suit emergency pressure of 180 millimeters of mercury. No more than two percent of carbon dioxide by volume at sea level should be permitted.21 Other limitations, including extremes of temperature, humidity, radiation, and accumulating toxic  gases from carbon monoxide, ozone, metal, and plastic fumes, also became "human parameters." Warning instruments in the capsule relied primarily on stimulating the astronaut's senses of sight and sound; psychologists also studied the feasibility of using his senses of touch and smell to aid him in diagnosing malfunctions.22
During the fifties academic and medical studies in sensory deprivation made an important, if indirect, contribution to the building of the spacecraft and the training of the astronauts. Made notorious by the experience of American prisoners of war who had been isolated and "brainwashed" in North Korean prison cells, the effects of isolation were attacked on many fronts. At McGill University, in Canada, at the University of Rochester in New York, and at the National Institute of Mental Health in Bethesda, Maryland, famous sensory deprivation experiments reduced all physical stimuli to near zero. Suspending people in water of body temperature in blacked-out, soundproof rooms at Bethesda revealed that normal men, regardless of their motivations, could hardly stay both conscious and sane if deprived of all sensory stimuli beyond three hours. Physicians and psychiatrists were warning in 1956 and 1957 that
if one is alone enough and at levels of human and physical stimulation low enough, the human mind turns inward and projects outward its own contents and processes. . . . Man's mental state is dependent on adequate perceptual contact with the outside world. . . . Isolation produces an intense desire for extrinsic sensory stimuli and bodily motion, increased suggestibility, impairment of organized thinking, oppression and depression, and in extreme cases, hallucinations, delusions, and confusion.23Such background studies strengthened aeromedical demands, originating outside NASA and STG, for continuous communications between the ground and an orbiting man, for increasing the number of meaningful cues to be given the man in space, and for accenting significant tasks to be performed by the man inside the capsule. There was room for controversy here, but STG and NASA believed the hypothetical risks did not justify the very large outlay of money, men, and time that a continuous communication network would have required.
If outside advice of this type was not always taken, there was still a conscious effort to solicit it. One of the most useful means of dialogue was the presenting of papers at meetings of professional societies. The size, lead time, and innovating nature of Project Mercury, together with the impetus from NASA's open information policy, all reinforced the normal professional obligation to inform and meet the judgment of one's colleagues. Thus it was that, on January 25, 1960, several leading engineers from the Space Task Group were in New York for the annual meeting of the Institute of Aeronautical Sciences and presented papers reviewing the scope and recent results of their research and development program.24 In one of these, Charles W. Mathews set forth the operational plans for the orbital mission. He did not mention the role of the pilot until the end  of his remarks. He then offered a summary list of eight activities to illustrate what the astronaut must be prepared to do: the Mercury pilot should communicate with ground stations, make scientific observations, monitor onboard equipment, control capsule attitude, navigate and fire retrorockets, initiate emergency procedures, activate escape system if necessary, and deploy landing parachute if required. Any one of these activities could conceivably save the mission.25
The degree of control over his own destiny that the astronaut might have during the first orbital flights steadily increased throughout 1959 by virtue of the development of two new semi-automatic control systems: fly-by-wire, interposed in the automatic stabilization and control system (ASCS), and the rate command system (rate stabilization control system, or RSCS), superimposed on the manual proportional control system. Further elaboration and sophistication of the hardware took account of man's flexibility by providing for the use of more than one system at a time. In addition to the "last resort," or manual-proportional, method of attitude control, other uses of the astronaut as a source of mechanical power were being incorporated to the mutual advantage of reliability and flexibility. Turnkey handles and pull rings were added to duplicate virtually every automatic function of the mission sequence.
In April 1960, Edward R. Jones, the chief psychologist at McDonnell, feeling that a vigorous defense is the best defense, argued in public that man in the Mercury capsule not only could act as an observer as well as the observed but should be considered an integral part of the system to increase the probability of mission success. Having just completed extensive studies of man's vision from the new centerline window, Jones supervised studies of other expected sensations during the Mercury orbital flight.26 As the hardware and manned capsule systems tests progressed, Jones had more reason for his optimism about man's ability to perform effectively in space, once his life-support requirements were met. Concerning higher mental processes, Jones, speaking in a symposium at the Iowa Academy of Science, where James A. Van Allen represented the instrumentalists and John Paul Stapp represented the experimental physicians, maintained his positive approach:
Most of the astronaut's tasks will involve complex mental activity even though some may be on a near reflex level as a result of constant practice. It is not expected that impairment of these functions will occur under normal vehicle operation. Stress and an abnormal atmospheric composition, if present, could cause some impairment of the higher mental functions.
It should be apparent that the training of the astronaut in the operation of the space vehicle will be critical. Much of the physiological training and conditioning will be given on a part task basis in human centrifuges, and pressure and heat chambers. The operation of the vehicle can be practiced over and over again in a capsule simulator . . . built for Mercury. Overlearning far beyond the point that apparent progress stops seems to be the best guarantee that the astronaut will have developed response patterns that are least apt to deteriorate under the stresses of orbital flight.27
14 Memo, White to Chief, Engineering and Contract Administration Div., "Project Mercury Full Pressure Suit Selection," Feb. 27, 1959. See also Frederick R. Ritzinger, Jr., and Ellis G. Aboud, "Pressure Suits - Their Evolution and Development," Air University Review, XVI (Jan.-Feb. 1965), 23-32.
15 Edwin G. Vail and Charles C. Lutz, "Project Mercury Pressure Suit Evaluation," Wright Air Development Center, June 1959; Lee N. McMillion, interview, Houston, Nov. 1, 1963; "Agenda and Conclusion, Pressure Suit Evaluation Conference," STG, July 15, 1959. Cf. "Status Report No. 3 for Period Ending July 21, 1959," STG.
16 William S. Augerson and McMillion, "Conclusions and Recommendations Concerning the Mercury Pressure Suit," Aug. 29, 1959; letter, STG to Langley Research Center, Attention Procurement Officer, "Project Mercury Pressure Suit Procurement," with enclosure, "Specification - Suit, Full Pressure, Project Mercury," Oct. 2, 1959. Cf. "Status Report No. 3."
17 W. J. Berus, "Space Suits - Past, Present and Future," paper, spring meeting, Akron Rubber Group, April 4, 1963, 15. See also "Status Report No. 3." Ventilation oxygen entered the suit through a hose connection at the waist, was channeled through suit distribution ducts to body extremities, and flowed freely over the body back to the helmet.
18 Memo, McMillion to Chief, Flight Systems Div., "Pressure Suit Status Report," Dec. 24, 1959.
19 D. D. Ewing, "Sizing Problem on Project Mercury Pressure Suit," notes on proposed revision of Contract No. AS 60-8011 C, Jan. 25, 1960; memo, McMillion, "Trip Report," March 1, 1960; memo, McMillion to Chief, Flight Systems Div., "Trip Report," June 3, 1960, with enclosure re decisions made in meeting at Goodrich plant, Akron, March 14, 1960. Cf. letter, Ewing to Carl F. Effler, "Report of Mercury Suit Meeting on June 1 and 2, 1960,-" June 7, 1960. "The complexity and difficulty of donning the full pressure suit was noted with covert satisfaction by the writer, 'an old-partial pressure suit man,' " said James P. Henry of STG in memo to Chief, Flight Systems Div., "Trip Report," May 6, 1960. Memo, McMillion to Faget, "Astronaut Comment on Pressure Suit," with enclosures, (1) agreements and (2) comments by astronauts, June 27, 1960.
20 Certainly the most delicate of all such interfaces for the first few leaps into space was that between the biosensors and human skins. The issue of the rectal thermometer designed into the suit was accepted for the moment as a necessary intrusion. See memo, Wheelwright to Chief, Flight Systems Div., "Trip Report," March 1, 1960; letter, Warren J. North to Harold I. Johnson, "Comments on Johnsville Centrifuge Program," Nov. 23, 1960.
21 Suit pressure was maintained by a demand regulator that metered the oxygen into the system. If cabin pressure failed, the demand regulator sensed the pressure loss, sealed the suit, and maintained it at 4.6 pounds. Should both systems fail - suit and cabin - there was an emergency oxygen valve that fed directly into the inlet hose at the waist junction. Before May 1961, the pressure suit had received 514 hours of manned testing.
Oxygen was metered into the cabin by a regulator to maintain a minimum limit of 5.1 pounds. In designed operation, the cabin system remained at ambient pressure on the pad and up to 27,000 feet. At that altitude it sealed off at 5.5 pounds. If there were a fire or a buildup of toxic gases, the astronaut could decompress the cabin manually, exhaust the toxic odors, and repressurize it. This system received 135 manned test hours at the Navy's Aviation Medical Acceleration Laboratory before May 3, 1961.
22 Thompson, "Physiological and Psychological Considerations for Manned Space Flight," 4, 24, 47-49, 164. See also White, "Progress in Space Medicine," paper, Second World and Fourth European Congress for Aviation and Space Medicine," Rome, Oct. 2 731, 1959.
23 D. G. Starkey, "Isolation," in "Physiological and Psychological Considerations for Manned Space Flight," 140-145. See also Philip Solomon, et al., "Sensory Deprivation, a Review," American Journal of Psychology, CXIV (Oct. 1957), 4.
24 See, for example, Johnston, "Mercury Life Support System"; Faget and Robert O. Piland, "Mercury Capsule and Its Flight Systems" and Bond and Alan B. Kehlet, "Review, Scope and Recent Results of Project Mercury Research and Development Program," papers, 28th annual meeting, Institute of the Aeronautical Sciences, New York City, Jan. 25, 1960.
25 Charles W. Mathews, "Review of the Operational Plans for Mercury Orbital Mission," paper, 28th annual meeting, Institute of the Aeronautical Sciences, New York City, Jan. 25, 1960.
26 Edward R. Jones, "Prediction of Man's Vision in and from the Mercury Capsule," paper, 31st annual meeting, Aerospace Medical Assn. Miami Beach, May 9, 1960.
27 Jones, "Man's Performance in an Orbital Space Vehicle," paper, Iowa Academy of Science, University of Iowa, Iowa City, April 22, 1960, 7, 10.