By C. Patrick Laughlin, M.D., Life Systems Division, NASA Manned Spacecraft Center; and William S. Augerson, M.D., Life Systems Division, NASA Manned Spacecraft Center.


The space flight of Mercury-Redstone 4 accomplished several life-science objectives. Specifically, a second United States astronaut experienced the complex stresses associated with manned space flight; physiological data reflecting the responses of a second United States astronaut to space flight were obtained; and additional experience was gained in the support of manned space flight which will influence procedures in subsequent operations.

The Space Flight Environment

After two attempts at launching in the 4 days preceding the flight, Astronaut Grissom entered the spacecraft at 3:58 a.m. e.s.t. on July 21, 1961. His preparation had proceeded smoothly, beginning at 1:10 a.m. e.s.t. as discussed in paper 5. He was wearing the Mercury full-pressure suit and was positioned in his contour couch in the semisupine position, with head and back raised approximately 10° and legs and thigs flexed at approximately 90° angles. This position was maintained until egress from the spacecraft after landing. One-hundred-percent oxygen was supplied when pressure suit connections to the spacecraft environmental control system were completed. The total time in the spacecraft during the countdown was 3 hours 22 minutes. During the extended countdown, Astronaut Grissom performed numerous spacecraft checks and "relaxed" with periodic deep breathing, muscle tensing, and movement of his limbs. At the lift-off signal, the Redstone launch vehicle ignited and accelerated smoothly, attaining a peak of 6.3 g at T +2 minutes 22 seconds. Then the spacecraft separated from the launch vehicle and gravity forces were abruptly terminated. A period of 5 seconds ensued while spacecraft turnaround and rate damping occured. During 5 minutes of weightless flight which followed, Astronaut Grissom was quite active in performing vehicle control maneuvres and with monitoring of spacecraft systems. He was, in his own words, "fascinated" with the view from the spacecraft window. The firing of the retrorockets at T +5 minutes 10 seconds resulted in a brief 1g deceleration. At T +7 minutes 28 seconds the 0.05 g relay signaled the onset of reentry, and deceleration forces climbed quickly to 11 g. Drogue and main parachute actuation occured at T +9 minutes 41 seconds and T +10 minutes 13 seconds, respectively, and a 4 g spike was seen with opening of the main parachute. Landing occurred at T +15 minutes 37 seconds, 7:35 a.m. e.s.t.

Suit and cabin pressure levels declined rapidly from launch ambient levels, as programmed, and stabilized at approximately 5 psia with the suit pressure slightly above cabin pressure. These pressures were maintained until snorkle valve opening at T +9 minutes 30 seconds during parachute descent.

Suit inlet temperature ranged from 55° F to 62° F during countdown and flight and reached a level of 73° F approximately 9 minutes on the water after landing.

Monitoring and Data Sources

Medical monitoring techniques and bisensor application were identical with those utilized in the MR-3 mission (ref. 1). The total monitoring time was approximately 3 hours and 35 minutes, commencing with entrance of the spacecraft and ending in loss of signal after landing. Physiological data were monitored from the medical consoles in Mercury Control Central and the Redstone blockhouse, and signals were received during the later flight stages at Bermuda and on downrange ships. Again the astronaut's inflight voice transmissions and postflight debriefing were particularly significant as data sources. (Samples of inflight telemetry data recorded at various monitoring stations are shown in figs. 4-1 to 4-4.) In addition, the canceled mission of July 19 with 4 hours of countdown provided interesting comparative physiological data. Astronaut Grissom's physiologic responses to 17 Mercury-Redstone g-profile centrifuge runs were also available as dynamic control data. Unfortunately, the astronaut observer camera film was lost with the sunken spacecraft.

Blockhouse Telemetry Record

Figure 4-1.   Blockhouse telemetry record obtained during countdown (5:43 a.m. e.s.t).

Mercury Control Center Record

Figure 4-2.   Mercury Control Center record during launch phase (00:30 to 00:45). First part of record at 25 mm/sec, second part at 10 mm/sec.

Bermuda Mercury Station Record

Figure 4-3.   Bermuda Mercury Station record (10 mm/sec) taken just before 0.05 g as period of weightlessness was nearing end.

Telemetry-Aircraft Record

Figure 4-4.   Telemetry-aircraft record obtained 9 minutes after reentry.

Results of Observations of Physiological Function

Figures 4-5 and 4-6 depict the pulse rate during the countdown, tabulated by a ten-second duration pulse count for each minute and count time. Pulse rates occurring at similar events in the canceled mission countdown are also indicated. The countdown pulse rate ranged from 65 to 116 per minute until shortly before lift-off. As plotted in figure 4-7, pulse rate began accelerating from T -1 minutes through launch, attaining a rate of 162 beats per minute at spacecraft separation and turnaround maneuver. Some slight rate decline trend was apparent during the first 2 minutes of weightlessness, returning to a high of 171 beats per minute with retrorocket firing. The pulse rate was above 150 beats per minute during all but a few seconds of weightlessness. Pulse rate declined slightly following reentry deceleration and then fluctuated considerably during parachute descent and was 137 beats per minute on landing. All inflight pulse rates were determined every 15 seconds, counting for ten-second durations.

Pulse and Respiration Rates

Figure 4-5.   Pulse and respiration rates during countdown (4:00 to 5:30 a.m. e.s.t).

Pulse and Respiration Rates

Figure 4-6.   Pulse and respiration rates during countdown (5:40 to 7:20 a.m. e.s.t).

Electrocardiographic trace quality from both sternal and axillary leads was quite satisfactory during countdown and flight. Sinus tachycardia and occasional sinus arrhythmia were present. No abnormalities of rhythm or wave form were observed.

Respiratory rate during countdown varied from 12 to 24 breaths per minute as shown in figures 4-5 and 4-6. Unfortunately, respiratory trace quality, which had been quite acceptable during countdown, deteriorated during most of the flight, precluding rate tabulation. Some readable trace returned late in the flight, and a high of 32 breaths per minute was noted.

Body temperature (rectal) varied from 99.5° immediately after astronaut entry into the spacecraft to 98.6° just before launch. There was a gradual increase to 99.2° in the latter phases of flight. These changes are considered to be insignificant, and, subjectively, temperature comfort was reported to be quite satisfactory during the countdown and flight.

Astronaut Grissom made coherent and appropriate voice transmissions throughout the flight. At the postflight debriefing, he reported a number of subjective impressions gained while in flight. He noted that the vibration experienced at maximum dynamic pressure was "very minor" and did not interfere with his vision. A brief tumbling sensation was noted at launch-vehicle cutoff. This sensation was only momentary and was not accompanied by nausea or disturbed vision. A distinct feeling of sitting upright and moving backward was described and the sensation reversed to forward travel with retrorocket firing. This orientation may have been related to his position relative to Cape Canaveral; that is, observing the Cape receding behind through the spacecraft window. No disturbances in well-being were reported during the flight and the absence of gravity produced no specifically recognized symptoms. The astronaut was not aware of his heart beating throughout the mission. Hearing was adequate throughout the flight according to pilot reports and voice responses. Near and distant visual acuity and color vision appeared to be normally retained. The jettisoned escape tower was followed for several seconds through the spacecraft window and a planet (Venus) was observed just before burnout. Vivid contrasting color was reported during observation of the sky and earth. The programed turnaround and other maneuvers of the spacecraft produced changing levels of illumination within the cabin, necessitating considerable visual adaptation.

Improved environmental control system instrumentation permitted a determination of astronaut oxygen consumption during the countdown. This was calculated to be about 500 cc/min. A very high usage rate was noted during flight as a result of system leakage, and metabolic utilization could not be determined.

Astronaut Grissom's Mercury-Redstone centrifuge pulse rates were tabulated and are presented graphically in figure 4-7 for comparison with the flight pulse data. The highest rate noted for his centrifuge experience was 135 beats per minute. Also shown in figure 4-7 are Astronaut Grissom's respiratory rate responses during four Mercury-Redstone centrifuge sessions.

Pulse and Respiration Rates

Figure 4-7.   Pulse and respiration rates during flight.


An evaluation of the physiological responses of the astronaut of the MR-4 space flight permits the following conclusions:

(1) There is no evidence that the space flight stresses encountered in the MR-4 mission produced detrimental physiological effects.

(2) The pulse-rate responses reflected Astronaut Grissom's individual reaction to the multiple stresses imposed and were consistent with intact performance function.

(3) No specific physiologic findings could be attributed to weightlessness or to acceleration-weightlessness transition stresses.


1. Henry, James P., and Wheelwright, Charles D.: Bioinstrumentation in MR-3 Flight. Proc. Conf. on Results of the First U.S. Manned Suborbital Space Flight, NASA, Nat. Inst. Health, and Nat. Acad. Sci., June 6, 1961, pp. 37-43.

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