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RESULTS OF THE SECOND U.S. MANNED ORBITAL SPACE FLIGHT, MAY 24, 1962

 

5B. PHYSIOLOGICAL RESPONSES OF THE ASTRONAUT

 

By ERNEST P. McCUTCHEON, M.D., Aerospace Medical Operations Office, NASA Manned Spacecraft Center; CHARLES A. BERRY, M.D., Chief, Aerospace Medical Operations Office, NASA Manned Spacecraft Center; G. FRED KELLY, M.D., U.S. Naval Air Station, Cecil field, Jacksonville, Florida; RITA M. RAPP, Life Systems Division, NASA Manned Spacecraft Center; and ROBIE HACKWORTH, Aerospace Medical Operations Office, NASA Manned Spacecraft Center

 

[54] Summary

 

The MA-7 mission provided an appreciable extension to the observation of man's physiological responses to space flight. The stresses of space flight appeared to have been well tolerated. All flight responses are considered to be within acceptable physiological ranges. Specifically, the heart-rate response to nominal exercise demonstrated a reactive cardiovascular system. An aberrant. ECG tracing was recorded during reentry and is believed to have resulted from the increased respirator, effort associated with continued speech during. maximum acceleration. No disturbing body sensations were reported as a result of weightless flight. Astronaut Carpenter felt that all body functions were normal. Solid foods can be successfully consumed in flight, but precautions must be taken to prevent crumbling. The biosensors provided useful ECG data, with minimal artifact. The respiration rate sensor provided good prelaunch but minimal in-flight coverage. Because of erratic amplifier behavior, the rectal temperature thermister gave invalid values for approximately - one-third of the flight. At the present time, the in-flight blood pressure cannot be interpreted.

 

Introduction

 

The three-pass mission of Astronaut M. Scott Carpenter has added a second 4 1/2-hour increment to the time that man's responses to orbital flight have been observed as a part of project Mercury . There were a number of aeromedical objectives continued from the MA-6 flight including additional study of man's physiological and psychological responses to space flight, i.e., exit and reentry accelerations, weightlessness, weightless transition periods, and an artificial environment.

Although the general objective for each flight are similar, there are many specific differences. One of the most important medical variables from flight to flight is the normal physiological differences between pilots. Preflight, in-flight, and postflight comparisons for a particular individual can be made in some detail, but only general comparisons with results from previous flights with other subjects are possible. Projections of the flight responses of a new astronaut must include considerations of this important variable.

Data were obtained from clinical examinations, bioinstrumentation, and subjective inflight observations. The data and analysis from subjective in-flight observations and bioinstrumentation are contained in this part of the Aeromedical Studies paper. Since the pilot's physiological responses cannot be completely separated from his environment, the discussion in paper 1 regarding the environmental control system complements the following analysis.

 

Mission

 

The astronaut's activities during the countdown have been discussed in section A of this paper. The transfer van arrived at the launch pad at 4:11 a.m. e.s.t., where the astronaut waited 19 minutes until it was time to ascend the gantry. Insertion into the spacecraft occurred at 4 :44 a.m. e.s.t. and physiological monitoring began. The astronaut, wearing the Mercury full- pressure suit, was positioned in his contour couch in the semisupine position and secured by shoulder and lap harnesses. His position, in relation to the spacecraft, [55] remained stationary throughout the flight. For both launch and reentry, the spacecraft is oriented such that the contoured couch is in a plane 90° from the direction of acceleration, which results in the astronaut s being exposed to acceleration transversely, or through the back.

The spacecraft cabin and suit environments were maintained at nearly 100-percent oxygen throughout the flight until the air inlet and outflow valves were opened after reentry. Opening these valves permits the introduction of ambient air. Spacecraft cabin and suit pressures were at ambient levels until launch and then declined to the nominal regulated pressure of 5.1 psia. They remained essentially constant until the pressure relief valve opened at an altitude of 27,000 feet.

The astronaut's total time in the spacecraft while on the launch pad was 3 hours and l minute. During this period,, spacecraft preparation and final preflight checks were completed, and the astronaut performed frequent deep-breathing and muscle-tensing exercises.

After a 45-minute hold, the spacecraft was launched at approximately 7:45 a.m. e.s.t. and the flight proceeded as planned. The accelerations of powered flight occurred in two phases. The first phase occurred in the first 129 seconds from lift-off to booster engine cutoff (BECO) and varied progressively from 1 g to 6.5 g. The second phase occurred at the time interval from 130 to 181 seconds which is from BECO to sustainer engine cutoff (SECO). In this phase the accelerations varied smoothly from 1.3g at 130 seconds to 7.8g at 181 seconds. The period of weightlessness began at 5 minutes and 10 seconds after launch and lasted for 4 hours and 39 minutes.

Reentry acceleration began 4 hours and 44 minutes after launch and increased gradually to a value of 7.5 g, which occurred at 4 hours and 48 minutes ground elapsed time. The buildup from 1 g and return to 1 g occurred over a period of 3 minutes and 30 seconds. The spacecraft landed on the water at 12:41 p.m. e.s.t., 4 hours and 56 minutes after launch.

 

Monitoring and Data Sources

 

Physiological data for the MA-7 mission were acquired by utilizing methods and sources similar to those used in previous Mercury manned flights. (See refs.1 to 3.) Data from the Mercury-Atlas three-orbit centrifuge simulation, conducted in September 1961, provide a dynamic experience to compare with the flight data. Recent data for establishing baseline responses were obtained from Astronaut Carpenter's simulated launch for the MA-6 mission and from launch-pad simulated flights in the last weeks before the MA-7 launch. Flight data included the range medical monitor reports, pilot's reports of special tests performed, biosensor data, and voice transmissions. The biosensor data were recorded continuously from 6 minutes before lift-off until bioplug disconnect at 3 minutes prior to landing. The astronaut s voice was recorded from 6 minutes before lift-off until landing. The pilot-observer camera film and the postflight debriefing were additional data sources.

 

Bioinstrumentation

 

The biosensor system consists of two sets of electrocardiographic leads, ECG 1 (axillary) and ECG 2 (sternal); a rectal temperature thermistor; a respiration-rate thermistor; and the blood-pressure measuring system (BMPS). The only change from MA-6 flight was the replacement of the manual BPMS with a semiautomatic system as discussed in paper 1.

All sensors operated normally during the countdown except the BPMS. Some 34 minutes prior to lift-off, 3 cycles of the BPMS demonstrated intermittent contact in the microphone cable, but later cycles near lift-off were normal. Twenty -four blood-pressure cycles were obtained in flight. At the present time these records cannot be interpreted. The BPMS and procedures in its use are being extensively investigated in an effort. to obtain accurate inflight blood pressure values.

Figure 5-4 shows a blood-pressure trace from the blockhouse record at 5:52 a.m. e.s.t.. 68 minutes prior to launch. A summary of blood-pressure data is presented in table 5-X.

During the flight, body movements and profuse perspiration caused a large number of FCG artifacts, but the record was interpretable throughout the mission.

The respiration rate sensor provided useful preflight information but in-flight coverage was minimal.

 


chart of heart and repiration measurements

[56] Figure 5-4.- Bioinstrumentation from blockhouse records (T-68 minutes).

Speed of tape-recorder was 10mm/sec.


Table 5-X.- Summary of Blood-Pressure Data.

Data Source

Number of values

Mean blood pressure, mm Hg

Standard deviation, 2 [Greek letter sigma]

Systolic range, mm Hg

Diastolic range, mm Hg

Mean pulse, mm Hg

Systolic

Diastolic

Preflight physical exams

18

119/73

14

15

98 to 128

58 to 84

46

3-orbit Mercury-Atlas centrifuge examination

30

130/83

22

15

104 to 155

72 to 106

47

Launch-pad tests

45

127/64

31

18

101 to 149

44 to 84

63

MA-7 countdown

13

116/63

18

12

105 to 139

56 to 70

53

Preflight totals

106

125/71

24

14

98 to 155

44 to 106

54

Postflight physical exams

3

115/76

2

9

114 to 116

70 to 80

39

 


[
57] Figure 5-5.- Bioinstrumentation in flight.

 

[58] The instability of the body temperature readout is believed to have been the result of erratic behavior of the amplifier from 59 minutes to 2 1/2 hours after launch, approximately one-third of the flight. This erratic period is shown as a shaded area in figure 5-5. The values at all other times are considered valid.

The pilot-observer camera film, as a result of postlanding immersion in sea water, was of poor technical quality and limited usefulness.

 

Preflight

 

In order to obtain pertinent physiological baseline data on Astronaut Carpenter, certain preflight activities were monitored by the medical personnel. Table 5-XI lists these activities and their duration.

 

Table 5-XI. Launch Pad Test Monitoring

Simulated launch, MA-6, Jan.17, 1962

5:12

Simulated launch, MA-7, Apr. 30, 1962

4:00

Simulated launch, MA-7, May 10, 1962

3:15

Simulated launch, MA-7, May 15, 1962

4:50

Launch countdown, MA-7, May 24, 1962

3:01

Total

20:18

 

Figure 5-6 depicts the heart rate, blood pressure, respiration rate, body temperature, and suit-inlet temperature recorded during the MA-7 countdown. The values for the same physiological functions from the astronaut's MA-6 and MA-7 simulated launches are also shown and the occurrence of significant events is indicated. Heart and respiration rates were determined by counting for 30 seconds every 3 minutes until 10 minutes prior to lift-off, at which time 30-second-duration counts were made each minute. The minute-long counts were continued until orbital insertion.

During the simulated launches of January 17, 1962, and May 10, 1962, the heart rate varied from 48 to 78 beats/minute with a mean of 57 beats/minute. The respiration rate varied from 8 to 32 breaths/minute with a mean of 16 breaths-minute. The blood-pressure values, recorded in millimeters of mercury, showed a systolic range of 101 to 149 and a diastolic range of 44 to 84 with a mean of l35/62. These values were essentially the same. as those observed during the MA-7 countdown and are all within an accepted physiological range.

Examination of the ECG wave form from all preflight data revealed sinus arrhythmia, occasional premature atrial contractions (PAC), and rare premature v ventricular contractions (PVC). These are normal physiological variations.

During approximately 50 minutes in the transfer van on launch day, the astronaut s heart rate varied from 56 to 70 beats/minutes with a mean of 65. Respiration rate varied from 8 to 20 breaths/minute with a mean of 14. The ECG was normal. Other physiological values were not obtained.

 

Flight Responses

 

A summary of the in-flight physiological data is presented in table 5-XII.

The maximum heart rate observed during launch was 96 beats/minute. The increase from 84 to 96 beats/minute occurred within the first 30 seconds of flight and was not, therefore, associated with maximum acceleration. The heart rate during the weightless period remained relatively stable with a mean of 70 beats/minute. The maximum heart rate of 104 beats/minute was found at drogue parachute deployment, which occurred at the time of maximum spacecraft oscillation. The mean rate during reentry was 84 beats/minute. All observed heart rates are well within accepted ranges.

The pilot's in-flight statement that he was comfortable and could not believe the telemetered body temperature readings of 102° F was helpful in the determination of the significance of these readings. The values in question are shown as a shaded area in figure 5-5 but are not included in table 5-XII. This increase in the astronaut's body temperature from 98° to 100.6° F during flight is physiologically acceptable and is believed to have resulted in part from an increased suit inlet temperature. A mild trend of gradually increasing body temperature...

 


[
59] Figure 5-6.- Bioinstrumentation in countdown and launch.

 

[60] Table 5-XII.- Summary of Heart Rate, Respiration Rate, and Body Temperature Data.

Data Sources

Hear rate, beats/minute

Respiration rate, breaths/minute

Body temperature, °F

Number of values

Mean

Range

Number of values

Mean

Range

Number of values

Mean

Range

All preflight data

408

57

42 to 84

354

15

5 to 32

128

99.3

98.3 to 101.5

Countdown

92

62

50 to 84

75

15

6 to 26

57

97.8

96.8 to 98.2

Flight:

Launch

7

87

82 to 96

5

16

10 to 20

4

98

98

Orbital

94

70

60 to 94

a 83

14

10 to 18

60

99.9

98 to 100.6

Reentry

15

84

72 to 104

a 9

19

16 to 24

15

100.4

100.2 to 100.5

a Values were obtained from the variation in the height of the ECG R-wave and are approximate only.

 

 

...has been observed in previous manned flights.

The respiration sensor did not provide useful information during most of the flight.. Approximate respiratory rates per minute were estimated by using variation in the height of the ECG R-wave and were within normal ranges.

Examination of the ECG wave form recorded during the flight showed an entirely normal record except for the following variations: There was a single premature atrial contraction (PAC) 13 seconds after SECO, followed by a beat showing suppression of the sinus pacemaker. A second PAC occurred 1 minute and 10 seconds before retrofire. At 04:48 :19 g.e.t., 21 seconds prior to maximum reentry acceleration, a 43-second period contained a number of cardiac pattern variations. These variations included premature atrial contractions with aberrant QRS complexes, atrial fusion beats, and short runs of four and five nodal beats. A sample of the nodal beats obtained during reentry is shown in figure 5-7. The remainder of the record d was entirely normal. During the period of maximum reentry acceleration, Astronaut Carpenter made a special effort to continue talking. The increased respiratory effort associated with continued speech during increasing acceleration is believed to have produced these changes. These irregularities did not compromise the pilot's performance.

 

Subjective Observations

 

Astronaut Carpenter stated that the flight was not physically stressful. He was subjectively hot and perspiring during the second orbital pass and the first half of the third pass but was never extremely uncomfortable.

During the acceleration-weightlessness transition phase there was no tumbling sensation. The pilot was impressed by the silence after separation and adapted quickly to the new environment. He described the weightless state as " a blessing-nothing more, nothing less." He compared the weightless state to that of being submerged in water. The Mercury full-pressure suit was comfortable in the weightless state. The pilot reported that there were no pressure points and that mobility was good. After the retrorockets ignited, the sensation was one of having stopped, rather than that of traveling in an opposite direction from flight as was reported in the MA-6 flight.

The astronaut was always oriented with respect to the spacecraft, but at times lost orientation with respect to the earth. When the horizon was not in view, it was difficult to distinguish up and down positions, but this was never of immediate concern to the astronaut. The only illusory phenomenon occurred just after orbital attitude was attained arid involved the position of the special equipment storage kit. At this time. the pilot had totaled from the horizontal to the vertical and was in a seated position relative to the earth's surface. The was surprised to find that the equipment kit had also totaled to this position and was very accessible. Tactile approximation with the eyes closed was the same as that on the g ground. There was no tendency to overshoot or under reach control switches on the spacecraft instrument panel.

 

 


chart of heart and repiration measurements

[61] Figure 5-7.- Onboard physiological reentry data.

 

No disturbing sensory inputs were reported during weightless flight. Violent head maneuvers within the limited mobility of the helmet were performed several] times in every direction without symptoms of disorientation or vertigo. Vision was normal throughout the flight, and colors and brightness of objects were clear and easily discernible. Distances severe estimated by the relative size of objects. There was no detectable change in hearing. Somatic sensations were normal and no gastrointestinal symptoms were apparent.

During flight, Astronaut Carpenter consumed solid food,, water, and a xylose tablet without difficulty. The solid food was in the form of bite size, 3/4-inch cubes with a special coating packed loosely ill a plastic bag and stored in the equipment kit. Since the crumbling was reported when he first attempted to eat, it is believed that the food was inadvertently crushed during final spacecraft preparation on the launch pad. The special coating having been broken, the food continued to crumble during flight. The pilot stated that the floating particles within the spacecraft were a potential inhalation hazard. Finally, the elevated cabin temperature caused the candy to melt. He reported the only difficulty was in getting the crumbled food particles to his mouth. Once in the mouth, chewing and swallowing of both solids and liquids were normal. Taste and smell were also normal.

A total of 1,213 cc of water was consumed from the mission water supply. An estimated 60 percent was consumed in flight and the remainder after landing.

Calibrated exercise was performed without difficulty at 03:59:29 g.e.t. Because of the overheated condition of the pilot, earlier scheduled exercises were omitted A hand-held bungee cord with a 16-pound pull through a distance of 6 inches was used. Use of this device for a [62] short period caused an increase of 12 beats per minute in heart rate with return to previous values within 1 minute The heart-rate response to this nominal exercise demonstrated a reactive cardiovascular system.

Attempts to produce autokinesis (illusion of vision due to involuntary eye muscle movements) were made on two occasions. Autokinesis was not produced but the tests were inconclusive.

 


References

 

1. DOUGLAS, WILLIAM K., JACKSON, CARMAULT B., JR., et al.: Results of the MR-4 Preflight and Postflight Medical Examination Conducted on astronaut Virgil J. Grissom. Results of the Second U.S.. Manned Suborbital Space Flight, JuIy 21, 1961. NASA Manned Spacecraft Center, pp. 9-14.

2. JACKSON, CARMAULT B., Jr., DOUGLAS, WILLIAM K., et al.: Results of Preflight and Postflight Medical Examinations 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. 31-36.

3. MINNERS HOWARD A., DOUGLAS, WILLIAM K., et al.: Aeromedical Preparation and Results of Postflight Medical Examinations. Results of the First United States Manned Orbital Space Flight, February 20, 1962. NASA Manned Spacecraft Center, pp. 83 92.


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