111: Height of Saturn V rocket in metres
On 16 July 1969, in the early hours of the morning, JoAnn Morgan drove into the parking lot at Pad 39a, Cape Canaveral, to oversee the fuelling of the giant Saturn V rocket. Against the darkness of the ocean behind, the spacecraft was bathed in the light of xenon arc lamps and enveloped in clouds of oxygen venting from the fuel tanks.
“It was an absolutely majestic sight,” says Morgan. “I stood out in the parking lot and watched it for a while because it was just so beautiful.”
At 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.
You might also like:
“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.”
Fuelled by liquid oxygen and kerosene, the rocket was made up of multiple stages. The lowest part of the rocket – or first stage – was fitted with five giant F-1 engines. Two further stages – and a total of six further engines – carried it into orbit. Above the engines were the compartment for the lunar lander, and then the service and command module for the three-man crew. The Saturn V was topped with an escape rocket, designed to blast the command module to safety if anything went wrong during launch.
“Gee whizz you think, did that thing really fly,” says Honeycutt. “Some hundred metres tall and then that little bitty thing up on the pointy end is all that came back – a pretty remarkable engineering achievement.”
The Moon rocket might have been even larger. Nasa’s original plan suggested developing a rocket called Nova. Fitted with eight F-1 engines, it would carry a larger, single spacecraft capable of landing on the Moon and then returning to Earth.
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.
During Apollo, it could take up to 16 hours to deliver the spacecraft the few kilometres from the VAB to the launchpad
“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.”
Although a driver sits in the cab, the heart of the crawler transporter is a control room. “It's really the brains and the nerve centre for the operators here,” says Dove. “The test conductor sets on the second console from the end and controls everything on the crawler.”
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.
(You can read more about the vehicles and their future here.)
35,000,000: Saturn V thrust at lift-off in Newtons
The Saturn V is the most powerful rocket ever successfully flown.
“I felt like we were on the point of a needle, a very large needle,” says Frank Borman, the commander of Apollo 8, the first manned flight to the Moon. “I had a feeling of being along for the ride rather than being in control of anything, the noise and vibrations gave you a feeling of enormous power.”
Apollo 8 ranks as one of the most audacious and risky missions in space history. Alongside Borman in the Apollo command module were Jim Lovell and Bill Anders, who gave the endeavour just a 30% chance of success.
Most seriously, the rocket started to pogo – creating forces on board that would most likely have killed any crew
The mission was considered such a risk because the previous, unmanned, test of the Saturn V – sometimes known as Apollo 6 – had not gone well. “The test flight that we flew right before [Apollo 8] was pretty much a disaster,” says Apollo flight director Gerry Griffin. “Almost everything went wrong.”
Most seriously, the rocket started to pogo – creating forces on board that would most likely have killed any crew. “We also lost some fuel lines,” adds Griffin, “and the upper stage engine didn’t restart.”
Over the next eight months, von Braun’s rocketry team set about solving all the problems, before convincing Nasa management the Saturn V was now safe to fly.
“It was gutsy on the part of the programme,” says Griffin. “It was also gutsy on the part of those three guys that got in there and rode the first ever Saturn V.”
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.
As the missions progressed, and the more stages they crashed, the more data they got back
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.
100: Percentage of cloud cover for the Apollo 12 launch
On 14 November 1969, four months after landing on the Moon, Nasa planned to do it again. On board Apollo 12: Pete Conrad, Dick Gordon and Alan Bean.
There had been a few rain showers that day, as a cold front moved across central Florida but meteorologists gave the go-ahead for launch and the countdown proceeded smoothly.
At 36 seconds after launch, as the Saturn V passed through the clouds, the electrical systems in the command module failed.
The switch flicked, the command module came back online
“What the hell was that?” exclaimed Conrad.
This was Gerry Griffin’s first shift as lead flight director, overseeing mission control.
“They had a master caution and warning panel with lights that said what was wrong and Conrad started reading that,” says Griffin. “The whole panel essentially lit up.”
As the rocket continued towards orbit, Griffin sought a solution. “This young man from a little college in southeastern Oklahoma named John Aaron, who was about 25 I'd guess, made a call, he said ‘tell him to try SCE to Aux.’”
Griffin had never heard of the switch but asked the Capcom, Gerry Carr, to relay the message to the spacecraft. “Conrad had never heard of the switch either so he said ‘SCE to Aux what the hell is that?’, but Al Bean knew where the switch was, right in front of him.”
The switch flicked, the command module came back online. And once the guidance computers were reset, the crew head for the Moon.
When engineers later analysed the launch, they discovered the rocket had generated its own lightning, the exhaust creating a circuit between charged particles in the clouds and the ground. Fortunately, the lightning didn’t affect the rocket’s separate computer which, throughout the drama, kept the spacecraft on track.
“It was really funny to listen to the crew after that,” says Griffin. “They get giggly, it was like a near accident in an auto… it was funny almost all the way to orbit.”
Join more than one million Future fans by liking us on Facebook, or follow us on Twitter or Instagram.
If you liked this story, sign up for the weekly bbc.com features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Culture, Capital, and Travel, delivered to your inbox every Friday.