From 1964—“The Saturn V S-II Second Stage”

The second stage of the Saturn V rocket, designated S-II, was one of the most advanced and risky rocket development projects of its era. It was the first large rocket stage to be powered by liquid hydrogen and oxygen, using a cluster of five J-2 engines producing one million pounds-force (4400 kN) with a specific impulse of 421 seconds. The stage was phenomenally light: when fully fueled, it was 92.4% propellant by weight. To reduce mass, it employed integral fuel tanks where the weight-bearing walls of the stage doubled as tank structure, and a common bulkhead separating the liquid hydrogen and oxygen tanks which, due to the great temperature difference between their contents, required a light but very effective insulation between them.

The S-II stage posed many engineering challenges and its development was troubled, protracted, and expensive. The first Saturn V pathfinder vehicle was initially stacked with a spool-shaped mass simulator because its S-II stage was not yet available. This film, produced by S-II prime contractor North American Aviation (who also built the Apollo Command and Service Modules), appears to be an internal morale-boosting effort for the company and its subcontractors, made at a time where the difficulties with the project were beginning to become apparent.

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I believe the Downey plant site now has a Walmart and a Kaiser Permanente hospital.