Saturn C-4

• Boeing (S-IB)
• North American (S-II)
• Douglas (S-IV)}} |country-origin = United States |cpl-year = 1985 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 218,000 lb to low Earth orbit and send 70,000 lb 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 67,000 lb Apollo Command/Service Module into lunar orbit, but it would not have been able to carry the 32,000 lb 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.

A December 1961 version called Saturn C-4B would have consisted of a IC C-4B first stage, a S-II C-5A second stage and a S-IVB C-5A third stage. It would have been capable of sending a 31,000 kg (68,000 lb) payload to a translunar trajectory.