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View of the stage's ambient helium spheres.

Picture 1 of 3.

The ambient helium spheres on the Saturn V's S-IVB were used to repressurize the S-IVB's propellant tanks after the orbital coast, prior to trans-lunar injection. This particular S-IVB was the dynamic test stage, and so differs from a flight S-IVB in a number of ways, including the number, positioning, and attachment method of the ambient helium spheres.

Also note the hydrogen feed line from near the center of the thrust structure to the 2:00 position, and the dart-shaped hydraulic system's accumulator reservoir at the 12:00 position.