The flight profile included maximum accelerations of about 10 to 12 g and periods of about 3 minutes at 0±0.02 g. The peak altitude obtained in the last ballistic flight was about 280 000 feet. The experimental capsule was pressurized at 1 atmosphere with 100 percent oxygen at the start of the experiment and fell to just below a half atmosphere of oxygen due to breathing during flight. The capsule temperature was kept between 10° and 20° C in both flights. The measurements taken from the rhesus monkeys were the electrocardiogram, respiration, body temperature, eye movements, and bar pressing, but only partial results were obtained in the first flight. Oxygen tension, total pressure, capsule temperature, and relative humidity were recorded. Both animals were recovered alive and did not show pathologic alterations in their physiologic and psychological reactions. MERCURY ANIMAL TEST FLIGHTS In the Mercury animal test program a Redstone missile carried the chimpanzee Ham on a ballistic flight to a height of 155 miles to provide animal verification of the success with which the Mercury system could be applied to manned flight. The male chimpanzee was trained to perform a two-phased reaction task during the 16 minutes of flight. The chimpanzee Enos was put into orbit for 3 hours and 20 minutes. Results of the two flights gave the following information: (1) Pulse and respiration rates during both the ballistic (MR-2) and the orbital (MA-5) flights remained within normal limits throughout the weightless state. Effectiveness of heart action, as evaluated from the electrocardiograms and pressure records, was also unaffected by the flights. (2) Blood pressures, both arterial and venous, were not significantly changed from preflight values during 3 hours of the weightless state. (3) The performance of a series of tasks involving continuous and discrete avoidance, fixed ratio responses for food reward, delayed response for a fluid reward, and solution of a simple oddity problem was unaffected by the weightless state. (4) Animals trained in the laboratory to perform during simulated acceleration, noise, and vibration of launch and reentry were able to maintain performance throughout an actual flight. From the results of the MR-2 and MA-5 flights, the following conclusions were drawn: