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View of the ambient helium spheres on the stage's thrust structure.

Picture 1 of 3.

The ambient helium spheres were used for stage repressurization after the S-IVB inserted the Apollo spacecraft into Earth orbit and before the translunar injection burn.

This stage was not manufactured as a flight article, but rather as the dynamic test stage. It was fitted with dummy mass simulators rather than actual helium spheres. I am uncertain what these helium spheres are or why they are mounted in a substantially different method than on the flight article.