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Two orbits later, medics on the ground, following Cooper's heart rate by telemetered data, saw it surge momentarily from 60 to 100—and figured he was having some sort of exciting dreams. Cooper at first denied it, but on landing confirmed that he had dreamed, even though he could not remember the plot. He awoke after 7½ hours of sleep, before a ground-triggered signal in his headset would have roused him. After an earlier snooze in flight, he awoke to find his weightless arms extended, as had some of the Soviet cosmonauts. From then on, Cooper tucked his hands under his restraining shoulder straps before sleeping to keep from moving any control switches accidentally.
The Guinea Pig. Cooper's mental and physical reactions were, of course, focal to the flight—and to the future of man in space. During his voyage, he conducted—or served as the guinea pig for—a variety of experiments. While previous astronauts used rectal thermometers. Cooper had a thermometer attached inside his helmet, opened his visor several times to pop it in his mouth. He pressed a button on his control panel to inflate a cuff on his arm and record his blood pressure just before and after pulling on a rubber exerciser. He tried some dehydrated food, including roast beef, which he squeezed out of small plastic bags after adding water through a nozzle. He experienced some difficulty, however, in both eating and drinking.
Doctors were particularly interested in urine checks, since Russian physicians had reported significant accumulations of calcium in the urine of their space travelers. This led to the theory that prolonged space flight might adversely affect human bones. Urine samples were collected in a "motorman's pal" attached to the lining of Cooper's space suit. His special preflight low-residue diet retarded defecation.
Sensors attached to Cooper's chest monitored his respiration rate; others permitted electrocardiograph readings. These measurements were telemetered to earth.
Physicians at Cape Canaveral reported that all of the astronaut's physiological functions were normal throughout his flight. Under the acceleration of liftoff, his pulse rose high to 150.
Elusive Light. Other experiments were specifically designed to furnish information for the future two-man Gemini or bital project and the later Apollo mission to the moon. To check visual sighting in space—vital to any in-flight rendezvous between spacecraft—Cooper ejected a 10-lb., 5¾-in. sphere carrying two bright flashing lights. Then, heading toward darkness near Africa on his third orbit, he failed to spot the sphere until he was near Hawaii on his fourth. "All of a sudden I saw it rising up from below me," he reported. "I could see it shining before I could see it flash, so apparently it had some light reflected off of it." When the sphere seemed about 18 miles away. Cooper said, it had the brightness of "a second-magnitude star." In another visual measurement test. Cooper tried to release a tethered balloon; the effort was unsuccessful because an explosive charge failed to fire and deploy the gear.