Saturn C-4
The Saturn C-4 was the fourth rocket in the Saturn C series studied from 1959 to 1962. The C-4 design was proposed in 1960 for a three-stage launch vehicle that could launch 99,000 kg to Low Earth orbit and send 32,000 kg to the Moon via Trans-lunar injection. It met the initial requirements for a lunar orbit rendezvous and lunar landing mission.
It would have consisted of three stages; an S-IB-4 first stage, a S-II-4 second stage and a S-IVB third stage. The first and second stages were essentially four-engine variants of the stages that would be used on the Saturn V, while the IVB stage was actually used on both the Saturn V and the Saturn IB.
It would have been capable of sending the 30,000 kg Apollo Command/Service Module into lunar orbit, but it would not have been able to carry the 15,000 kg Apollo Lunar Module as well. Although NASA eventually used the lunar orbit rendezvous method to go to the Moon, it decided to use the larger Saturn V which would provide a reserve payload capacity.
