Saturn S-2 Geneology Saturn S-II Genealogy Credit - © Mark Wade

Using the S-II had several advantages. It could be mounted atop a 'milk stool' and use the existing Saturn V launch gantry arms and plumbing for fueling and preparations (this approach was actually used later for Saturn IB launches for Skylab and ASTP). Discontinuing use of the Saturn IB would eliminate one rocket stage production line together with associated configuration and quality control headaches.

A dazzling array of combinations of S-II stages, S-IVB stages, and a variety of solid rocket motor strapons were considered. In most cases the S-II would have to be fitted with 'sea-level' versions of its J-2 engines, which were designed only for operation in near-vacuum conditions. This resulted in a decrease in engine performance. Since the S-II stage did not have enough thrust to get off the ground by itself, various combinations of solid rocket motor augmentation and propellant off-loads had to be used. The resulting configurations would have provided a payload range of between 13,000 kg and 66,000 kg to low earth orbit, thereby filling the payload gap and replacing the S-IB.

	Saturn INT-17	North American study, 1966. Saturn variant with a modified S-II first stage with seven high-performance HG-3 engines; S-IVB second stage. Poor performance and...more.
	Saturn INT-18	North American study, 1966. Saturn variant with Titan UA1205 or 1207 motors as boosters, Saturn II stage as core, and Saturn IVB upper stage. Various combinations...more.
	Saturn INT-19	North American study, 1966. Saturn variant with 4 to 12 Minuteman motors as boosters, Saturn II stage as core, and Saturn IVB upper stage. Saturn II stage would...more.