The Saturn V rocket was a remarkable achievement of human engineering. The man-rated rocket carried most of the Apollo missions into space, and won the Space Race for America.
It was also based on Nazi technology.
Wernher von Braun was an aerospace engineer and member of the Nazi Party during World War II. As the chief engineer of the Third Reich, he created a long-range ballistic missile called the V-2 rocket.
June 20 is a key date in his story, popping up twice. The first time was June 20, 1944, when the V-2 rocket became the first man-made object to cross the Kármán line, which lies 100 kilometres above Earth's sea level. On that day, it reached a jaw-dropping altitude of 189 kilometres.
From September 1944, over 3,000 V-2 rockets were launched, killing 2,754 civilians and around 4,500 military personnel. But this doesn't even scratch the human cost of actually producing the rockets -- they were constructed by concentration camp prisoners at the underground Mittelwork factory, and at least 13,000 (and as many as twice that number) of these slave workers were killed by beatings, starvation and execution.
This plan was changed when the war was winding down, and the US realised it could use Germany's scientists and engineers. Operation Paperclip, as it came to be known, was a secret program of recruitment, spiriting the top scientists out of Germany and into the US. This would boost American expertise, and keep that expertise from the Soviet Union and the UK.
This brings us to the second June 20, this time in 1945. It's the day the transfer of von Braun and his team was approved by the US Army. He and Arthur Rudolph, operations director at the Mittelwerk factory where so many died, went on to develop the Saturn V rocket, based on the work they had done on the V-2 ballistic missile.
In 1960, von Braun became the first director of NASA's Marshall Space Flight Center. An official NASA webpage declares him to be, "without a doubt, the greatest rocket scientist in history."
But it's worth remembering that these achievements came at a great cost of human lives, most of whom simply disappeared, remembered only as statistics.