On a bright Florida morning, a cylinder of thin ice the size of a grain silo is hanging 50 feet above the ground. The frost had started forming in the middle of the floodlit night, when the technicians at Cape Kennedy had started to fill the great tank at the top of the first stage of the Saturn V rocket with liquid oxygen—more than a million liters of it (260,000 gallons), at a temperature of minus 183°C (nearly 300 degrees Fahrenheit below zero). The wall of the tank and the skin of the rocket were one and the same, so water vapor from the humid Atlantic air had immediately started to freeze to the painfully cold metal.

As the oxygen was pumped in, some of it boiled off; vents at the top of the tank let the vapor out so that pressure within would not get too high. At 09:30, the vents were closed. Helium was pumped into the small space at the top of the tank. The pressure started to rise.

Below the oxygen tank was a slightly smaller tank filled with highly refined kerosene. Below that, arranged like the dots on the five face of a die, were the F-1 engines on which the success of the whole moon-project rested: exquisitely engineered, cunningly contrived, ludicrously powerful.

Adapted from The Moon: A History for the Future, by Oliver Morton. Buy on Amazon. The Economist

Two minutes after the vents were sealed, a valve at the bottom of the upper tank opened, and oxygen began to flow down into the F-1s. It took two different routes. Some of it went into gas generators which were linked to turbines which drove pumps. In the generators, it was mixed with kerosene and sparked alight. There was too much kerosene for the not-yet-full flow of oxygen to consume it all; the hot exhaust that the generators passed to the turbines was dirty black with part-burnt fuel. That didn’t stop it from spinning them up and bringing the engines’ pumps to life.

The rest of the oxygen went into the combustion chambers proper. There it met the kerosene-rich exhaust coming out of the turbines, and the mixture was set alight all over again. Black smoke began to billow from the bottom of the F-1s’ nozzles. The rocket began to shake. The pumps increased the flow of fuel and oxygen down into the fires below.

A carefully choreographed dance of temperature and energy was now under way. The turbo pumps used energy from the fuel burned in the generators to get ever more fuel into the combustion chambers, but they sent it there by way of a spiraling detour through tubes wrapped around the engines’ nozzles. This cooled the nozzles, which otherwise could not have borne the heat they were subjected to. It also warmed the fuel, which thus burned even better when, at last, it reached the combustion chamber. The fuel was also the lubricant for many of the engines’ moving parts—and the soot produced early on gave the lower section of the nozzle more protection from the heat of the growing flame within.

The pumps spun harder; the dance sped up. Five seconds after ignition, the fuel valves were fully open, and within a second or so the engines were close to full thrust. The central engine came to full power first, then the four outer ones. The fuel mix was now richer in oxygen, the burn cleaner and less sooty, more powerful. For a second or two after the last engine came up, the rocket was held down by mighty clamps. Then it was released.

All the rockets weight—almost 3,000 tonnes (about 3,300 tons) in all—now rested on the engines. They shouldered their burden and began to lift. The five arms from the tower that steadied and fed the rocket swung back. The shell of ice that had clung to the supercool metal fell in shattered sheets into the inferno below.