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111: Height of Saturn V rocket in metresAt 36 storeys high, the Saturn V ranks as one of the greatest technical and engineering achievements of the 20th Century. Its development was led by Wernher von Braun who, even while building V2 rockets for Hitler, dreamed of building a rocket to carry men to the Moon. “Not only was he technically competent,” says Jay Honeycutt, a rocket engineer and later senior manager at Nasa, “but he had great leadership skills and a great ability to communicate with government officials who funded the projects.”
2: Maximum speed of the crawler transporters, in miles per hour
The Saturn Vs were put together in the Vehicle Assembly Building (VAB), a structure so large it even has its own weather system. Engineers then had the challenge of getting the rockets to the launch pad, some five or so kilometres away. After an initial suggestion to float the spacecraft on barges, it was decided to build giant tracked vehicles called crawler-transporters.
With eight giant tracks – driven by 16 electric motors, powered by two generators – the crawler-transporters are more like ships than vehicles. And, like ships, the drivers are part of a team of operators and engineers that keep the vehicles moving slowly to the launch pad. Very slowly.
“The crawler has the power to go two miles an hour,” says driver Sam Dove. “However, you really don’t want to get it up to two, especially with a load on it – the most we ever go is one.”During Apollo, it could take up to 16 hours to deliver the spacecraft the few kilometres from the VAB to the launchpad. The time from pad to orbit was just eight minutes.
5: Saturn V upper stages on the Moon
Just nine minutes after launch, the Saturn V had already shed its first and second stages, sending them tumbling away towards the Atlantic Ocean. The third stage (rather confusingly known as the S4B), with its single engine, gave the spacecraft enough speed to reach orbit before shutting down.
Then, after one and a half revolutions of the Earth, the crew relit the S4B’s engine. In a manoeuvre known as Trans Lunar Injection, the rocket thrust the spacecraft out of orbit on a trajectory towards the Moon.
After the astronauts shut the engine down for a second time, and with the lunar lander extracted from the casing at the top, the rocket was abandoned. But – because it was travelling at the same speed and in the same direction as the spacecraft – unless the crew changed trajectory, the spent rocket would follow them to the Moon.
For the first few Apollo missions, Nasa’s solution was to send the S4B into orbit around the Sun. And, today, the S4B stages for Apollos 8, 9, 10 and 11 are still orbiting the Sun. Apollo 12’s upper stage, however, has been recaptured by the Earth’s gravity.
For the remaining missions, Nasa came up with a more imaginative plan.
The Apollo Lunar Surface Experiment Package (Alsep), left by the moonwalkers of Apollo 12 onwards, included a seismometer which relayed data to Earth. By smashing the S4B stages into the Moon, geologists could trace the resulting tremors through the lunar rock to help determine its geological composition.
As the missions progressed, and the more stages they crashed, the more data they got back. The Alseps continued to return data until 1977, when Nasa shut the programme down.