The medical data collection program for the last flight was developed on the foundation of knowledge gained from each of the preceding manned space missions. The suitability and the limitations of the Mercury spacecraft environments to meet the requirements of human physiology were better understood with each successive flight.
Thus, the final flight was approached with a better understanding of the likelihood of a given physiologic response occurring after exposure to the known stresses of space flight than had been previously possible. The opportunity for making valid medical observations during the MA-9 mission was further enhanced by the duration of the mission, as well as by the length of participation of Astronaut Cooper in the Mercury program, which provided an invaluable collection of baseline data prior to his actual flight.
For the MA-9 mission, the pilot-safety monitoring and data-gathering biosensor system consisted of two sets of electrocardiographic (ECG) leads, the impedance pneumograph, an oral temperature thermistor, and the blood pressure measuring system (BPMS). When oral temperature was desired, the pilot placed the small thermistor under his tongue for about 5 minutes. The remainder of the biosensor hardware was the same as that used for the MA-8 mission.
Astronaut Cooper withstood the stresses of the flight with no evidence of degradation of his functional integrity as a pilot. During his flight, he slept as part of the planned mission activities and subjectively reported that sleep was normal. Postflight examination of Astronaut Cooper revealed that he had developed dehydration. He also exhibited an orthostatic hypotension accompanied by an accelerated pulse. Approximately 9 to 19 hours after landing, the pulse and blood pressure responses returned to normal while the pilot was sleeping. A reversal of the ratio between neutrophils and lymphocytes was noted in the blood at an examination 4 days after the mission; the condition persisted for 2 weeks and then abruptly subsided. With respect to all other studies, the medical status of the pilot was found essentially unchanged between the preflight and postflight examinations.
Following the last Mercury mission, a listing of significant findings was derived from the medical operations of the Mercury program: (1) there was no evidence of significant degradation of pilot function attributable to space flight. A mission of 34 hours in the microgravity condition was well tolerated and all measured physiologic functions remained within anticipated ranges throughout the flight; (2) sleep inflight was possible and subjectively normal; (3) the radiation dose received by the astronauts was considered medically insignificant; (4) there was no evidence of abnormal sensory, psychiatric, or psychological response to an orbital space flight of up to 1.5 days; and (5) Following missions of 9 and 34 hours duration, an orthostatic rise in heart rate and fall in blood pressure was recorded, the implications of which were given very serious consideration as longer missions were undertaken.