The beginning of the S-II came in December 1959 when a committee recommended the design and construction of a high-thrust, liquid hydrogen fueled engine.

In 1961 the Marshall Space Flight Center began the process to find the contractor to build the stage.

Out of the 30 aerospace companies invited to a conference where the initial requirements were laid out, only seven submitted proposals a month later.

Plans were also developed to build 10 follow-on stages, S-II-16 through -25, but funding to assemble them never materialized.

It consisted of two aluminum sheets separated by a honeycomb structure made of phenolic resin.

[5] It was formed by welding 12 gores (large triangular sections) and two circular pieces for the top and bottom.

This change saved both weight and time and avoided the issues with air pockets entirely.

The S-II was constructed vertically to aid welding and keep the large circular sections in the correct shape.