Later she went out to the Michoud plant in New Orleans, where the big External Tanks were being constructed. She spent longer here; she was being encouraged to make the tanks a specialty during the mission.

The warehouses were immense caverns, big enough to hold the tanks in great cylindrical chunks. She watched the manufacture of a bulkhead, a huge dome which would cap the big liquid hydrogen tank. The dome came in pie-shaped aluminum slices called gores, which needed manufacturing precision far beyond the capability of any hydraulic press. So a forming die, with a flat sheet of aluminum on top, was sunk to the bottom of a sixty-thousand-gallon water tank, and a pattern of explosives was laid over the top. The gore was blasted into shape by surging shock waves.

York was awed by the scale of the enterprise. As she pursued her studies she became fascinated by the tanks, even though they were perhaps the most mundane item in the whole mission.

Each tank contained two massive, domed canisters, of propellant and oxidizer, connected by a cylindrical ring. The tanks were coated with four inches of polyurethane foam and reflective shielding, to reduce boiloff of the cryogenic propellants. Inside the tanks there were zero-G screens and cagelike baffles designed to stop the liquids sloshing during engine fire; the liquids were so heavy — more than two million pounds per tank — that the whole booster cluster could be thrown out of control by a severe enough slosh. And there were antivortex baffles, like huge propeller blades, to prevent the buildup of whirlpools — like those above the plug hole of a draining bath — that could suck bubbles of vapor into the feed pipes…

Because of the need for extreme reliability, and the extraordinary range of conditions a spacecraft faced, every component of Ares contained a hell of a lot more engineering than she’d expected from outside the program. Even these simple babies, the tanks. And because of the limited opportunities to test, traceability was essential: the ability to trace the life history of the humblest component right back to the ore from which it was smelted, to aid analysis in case of a failure.

It was the kind of attention to detail which passed by people — including Capitol Hill decision makers — who balked at the price of components NASA ordered. You want to spend how much, just on a goddamn gas can?

When she was at sites like Michoud — in the thick of the program — the discouragement of Romero’s resignation, and the skepticism, even downright hostility, of some sections of the press to the mission, all fell away from her. How could I turn down a Saturn? It would flawlessly hurl her to Mars, to perform experiments of huge importance. A billion dollars were being invested in her, a billion eyes would be on her to do a good job.