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Saturn V, the superlative rocket

The rocket groans and creaks. She blows white clouds into the shimmering air as if she were breathing. She trembles. She rears up like a racehorse that cannot wait for the starting gun. And the three men who are wedged in a capsule at the top of the 110 m long floor notice all of this. Every sound, every shock. But now, a few seconds before they are catapulted on a historic journey with more than 150,000,000 horsepower, there is nothing they can do about it. You can only trust that all of the people who were involved in the mammoth project called Saturn V did their best.

5.6 million individual parts

And there were many. Around 400,000 engineers, scientists and technicians worked between 1961 and 1969 on the rocket and spaceship that was supposed to shoot the three astronauts Neil Armstrong, Buzz Aldrin and Michael Collins towards the moon on the morning of July 16, 1969. The development team, recruited from among the employees of 20,000 companies and universities, had a clear mandate - a maxim that should also reassure the three men at the top of the rocket in the anxious seconds before the start: the engineers, so the requirement, were supposed to approach the limits of what was technologically feasible at the time, but they were never allowed to exceed them. Better safe and conservative than risky and overly complex. The result was a marvel of technology, composed of 5.6 million individual parts: a monstrous vehicle.
It starts with the five main engines, with their thrust of almost 3,500,000 kilograms. When they howl at the end of the countdown, the three men in the command module initially notice little of the immense power. The 3,000-ton rocket takes off slowly. Their tip sways back and forth as the thrusters try to keep their balance. After twelve seconds, the Saturn V finally leaves the launch tower behind. The way to the moon is free.

Your shock wave bursts windows

At this point, noise and vibrations also reach the first of the approximately one million spectators who have made a pilgrimage to Cape Canaveral. The shock wave of Saturn V literally goes through the bone. The pressure squeezes panes of glass out of a building at a distance of 18 kilometers. Even in New York, 1,500 kilometers as the crow flies from the launch site in Florida, where around 10,000 people have gathered in front of large screens in Central Park, earthquake measuring devices are still registering the vibrations. During the first test flight of the rocket, two years earlier, parts of the ceiling paneling in the press center, five kilometers from the launch pad, had even fallen down.

Even more would have been possible. Liquid hydrogen, cooled to -253 ° C, and the already existing liquid oxygen would have given the rocket additional thrust as a fuel mixture. However, in the early 1960s, when the main engines were designed, the technology was considered too risky, too immature. After all, an engine had to be developed that the world had never seen before and that is still today, more than 50 years later, the most powerful single engine ever built. Instead of the tricky hydrogen, the Saturn V engineers therefore opted for a tried-and-tested, not quite as powerful solution: They combined high-purity kerosene with liquid oxygen - a mixture that the Soviets used before Yuri Gagarin, the first space traveler, safely into space had brought.

13 tons of fuel consumption per second

Kerosene had another benefit for US engineers. Since the fuel is denser than hydrogen, its tank could be smaller and thus designed to be lighter. The dimensions were nevertheless gigantic: In order to provide space for almost 600 tons of kerosene, the tank had to be 13 meters high - higher than a single-family house.
The oxygen tank directly above was even bigger. With a length of almost 20 meters, it offered space for 1,250 cubic meters of the liquid gas, as much as fits in a 50-meter pool. Since pure oxygen is extremely reactive and even leaving a fingerprint on the tank walls can trigger an explosion, cleanliness was the top priority: The tanks were first rinsed, treated with acid, rinsed out again, milled thin, air-dried and finally subjected to chemical cleaning .
With a fuel consumption of 13 tons per second, which are pressed into the five engines shortly after take-off and generate a jet of fire almost 300 meters long, the tanks can be as large - their contents only last a short time: after two minutes and 41 Seconds, the Saturn V has just reached a height of 70 kilometers and can still be easily observed with binoculars, is already over.
The early end comes on purpose: A single rocket would be too heavy to ever reach the speed necessary to transport a 50-ton spaceship to the moon. The Saturn V therefore consists of three stages - basically three stacked, increasingly smaller rockets. If the first stage with its five engines and huge tanks is burned out, it is cut off and falls back to earth. The remaining rocket, now with only a third of its original take-off weight, can continue to pick up speed.

Saturn V - to this day one of the safest rockets

For the three men in their tight capsule, the step separation is tantamount to a train accident, as they will later put on the record. When the engines of the first stage, which the crew had previously pressed into the seats with four times their body weight, suddenly fall silent, the astronauts are thrown forward. Only the seat belts prevent the men from slamming on the dashboard of the capsule. Then, when the second stage fires, the acceleration suddenly resumes.
Since less thrust is required for the lighter rocket, the engines of the second stage no longer have to be so complex and sophisticated. This is why the rocket builders, led by the German engineer Wernher von Braun, took the risk of using hydrogen instead of kerosene.
The dangers have apparently been carefully considered. With 13 launches without a catastrophic mistake, ten of them with people on board, the Saturn V is still considered one of the safest spacecraft today. The flights of the largest, heaviest and most powerful of the rockets launched so far did not go without problems: The fuel mixture, which was pressed through more than 3,000 holes into the combustion chambers of the engines at a pressure of 60 bar and ignited there, often burned unstably. Some engines exploded on the test stand. The solution was simple: technicians drilled additional holes in the head of the combustion chamber according to a random pattern. There was additional turbulence and the problem disappeared.
During the first test flight, but especially with Apollo 13, another problem arose: The fuel masses in the second stage began to vibrate; the whole rocket started bouncing like a pogo stick. To be on the safe side, the middle of the five engines switched off. The on-board computer, which only managed 12,190 operations per second, less than a millionth of a today's processor, fortunately let the other engines run longer. The mission was to encounter further problems later in space, but the launch of the Saturn V was saved.