Some of the tests were more relevant to spaceflight. The medicos checked the balance mechanism in his ears, by pouring hot water into one ear, or cold water, and then swapping over. By watching his eyes, seeing if they flickered, the doctors claimed to be able to tell if the temperature differential made him dizzy, and how much.

He was put into a spinning chair, and told to close his eyes and tip his head up and down, from his knees to the head rest. A few minutes of this was enough to make him want to throw up, which, it turned out, was the idea.

Back at JSC, he was put through altitude chamber tests.

The chamber was a big metal box with thick glass portholes, through which protruded TV lights and cameras. It turned out that some of the cameras belonged to the doctors, and some to the press; such was the public interest in the mission he was already a reluctant media star.

He was taken up to a simulated forty-four thousand feet, and the air bled out of the chamber slowly. When the air was down to a quarter sea-level pressure, his lung sac expanded so much it ached; his bowels distended, making him fart explosively. Eventually the air pressure got so low he was forced to pressure-breathe into his oxygen mask: when exhaling, he had consciously to force air out of his lungs.

He had never in his life had to control, consciously, his breathing. It scared him.

They took him back to sea level. And then, without warning, they hit him with a rapid decompression test.

Suddenly he was at twenty-five thousand feet, and in the middle of a simulated bail-out. The air was sucked out of his lungs, and pain stabbed in his ears; when they returned the air, the room filled up with a cloud of condensed vapour.

He wasn’t sure what the surgeons were learning from such things. But he was learning, brutally, a lot more respect for his ex-wife and the other pilots.

The tests got tougher.