Lieutenant Colonel Philip Snow, Flight Surgeon, USAF, and Test Director of the Aero-Medical Laboratory, was pacing the study floor in his quarters, asking himself for the dozenth time in the past half-hour: What had happened to Richardson during the test that afternoon?
He was no stranger to problems. He had been living with them for the past few years, and they had been problems the like of which had never before challenged the ingenuity of man. For he was the head of a small community of men, scientists like himself—medical specialists of all kinds, psychologists, electronic technicians, physicists, pressure engineers, mathematicians and so on, each one of them an acknowledged expert in his particular field—who had worked together with one end in view: to send a man into space and bring him back safely to Earth again. To put it more excitingly: to enable man to take his first step toward the conquest of the universe.
The result of their labors to date was the Capsule, a bottle-shaped contraption which occupied the center of the laboratory floor.
It wasn't very big; just big enough to contain a man enclosed in a spacesuit, lying on a couch surrounded by instruments. But there wasn't a square inch of the capsule itself, the spacesuit, and the instruments which hadn't presented innumerable problems, the solving of which had been the result of endless research and theorizing and testing.
And in the same way, and almost to the same extent, there wasn't a square inch of the man, too, which didn't present problems, all of which must be solved before he could be sent into space.
And so, in test after test, one of the chosen astronauts had lain on the couch in the capsule, wired through his spacesuit to the dozens of dials and graph recorders on the consoles at which sat the watching specialists. It seemed there was nothing that could happen inside his body that they could not know about. They could read every flexing of his muscles, every heartbeat, every tiny shifting of temperature, every reaction of his blood and of his complicated nervous system. On the encephalograph, they could even detect reactions in the mass of gray matter which was his brain, any sign of tension there, and above all, any symptom of that strange phenomenon of which so little was yet known, and which was called the "breakoff"—the eerie sensation of complete isolation from Earth, the trancelike apathy and indifference to survival that can attack not only high-flying pilots, but deep-sea divers, "the rapture of the depths," and sometimes it was accompanied by hallucinations in which strange forms and sounds were seen and heard.

In the case of Lieutenant Hamilton Richardson, USN, there had been no mysterious troubles of this kind—in fact, no troubles of any kind at all. Aged thirty-six, he had been one of the first of the astronauts to volunteer. He had passed with flying colors every one of the grueling preliminary tests, mental and physical, and as far as could be judged by science, he had seemed to be the perfect specimen, mentally and physically, for the job. In the many tests made with him inside the capsule, nothing had gone wrong with him. There had been no signs of fatigue or failure of any kind. Had Snow been asked who, in his opinion, would be the first man—or, at any rate, the first American—to go into deep space, he would unhesitatingly have nominated Richardson. That is to say, until that afternoon when the thing had happened.
It had been a long test, one made for the first time. The object of it was to find out how the spacesuit, which was sealed off from the rest of the capsule, would stand up if something happened to the capsule itself. If, for instance, in its headlong flight through space, something struck it, something, maybe, no bigger than a small pebble. The odds were that in collision with even so small a meteor, the shell of the capsule would be punctured, and within a minute or less, the atmospheric pressure inside it, fixed at about five thousand feet above sea level, would be reduced to zero. In other words, the capsule would become a vacuum in which nothing on Earth could live. The astronaut would then have to depend upon his spacesuit which, being pressurized, and being really a capsule within a capsule, with its own supply of oxygen, would be the one hope of survival.
That day, the test had consisted of the "puncturing" of the capsule. At a given signal, the pressure inside it had been reduced to that of fifty miles above the Earth's surface—in other words, to zero—by pumping out the air inside it. Richardson, the ace of the astronauts, had been chosen for this important test.
It had gone well. With the other scientists at their dials, Snow, seated at the big console of literally dozens of dials, the only one to be connected with Richardson by sound and speech, had given the signal. In a minute, the capsule had become a vacuum fifty miles above the surface of the Earth, outside its envelope of atmosphere.
Richardson's voice, reading his instruments, acknowledging Snow's instructions, answering his questions, had come through as normal and as calm as ever. Snow had felt a rising excitement as the test proceeded.
And then, without warning, the thing had happened. Richardson's voice had stopped in the middle of an instrument reading, as if it had suddenly been cut off. A few seconds later, it had resumed. ............