Project Mercury had demonstrated forcibly that. man could survive and function ably as a pilot-engineer-experimenter in the space environment without, undesirable reactions or detriment to normal body functions for periods of as long as 34 hours.  Other medical knowledge gained included the fact that there had been no evidence of abnormal sensory, psychiatric, or psychological response to an orbital space flight of up to 1½days.  Sleep in flight was proved to be possible and subjectively normal.  The radiation dose received by the astronauts was considered medically insignificant.

Following missions of 9 and 34 hours’ duration, there was an orthostatic rise in heart rate and fall in blood pressure, which persisted for between 7 and 19 hours after landing.  The changes following the 34-hour flight were of greater magnitude than those following the 34-hour flight, but all changes disappeared in a similar time interval in both cases.  The implications of this hemo-dynamic response obviously would require serious study prior to answer, longer space missions.  No other clearly significant changes were found in the comprehensive preflight and postflight physiological examination.

Certain basic problems in space medicine remained unresolved, although investigators were now in a much better position to utilize improved biomedical instrumentation and to establish experimental designs having greater potential for solving these problems.  What, would be the effects of prolonged weightlessness and combined stresses upon the astronaut?  What would be the effects of space radiation?  Would toxic hazards within the spacecraft danger the safety of the astronaut?  Some basic biological questions had to be answered.  How would man survive for extended periods of time in a closed ecological system?  Could his food and wastes be recycled and regenerated?  Problems of biotechnology, too, were still unsolved.

All these fundamental problem areas had been defined in the late 1940’s by Strughold and his group at the School of Aviation Medicine, Texas, on the basis of the German aeromedical experience at Peenemunde, and logically on man’s historical ability to observe.  In this sense, space medicine may indeed have been said to antedate aviation medicine.

Be that as it may, the problem had been defined long since.  Project Mercury had provided the first step in answering them.  Simulation and testing on centrifuges could provide a partial answer, but only through actual experience in orbiting space laboratories could the larger answers be provided.  As Project Mercury drew to a close, the scientific community looked forward with confidence to meeting that challenge.