The Saturn C-3 was the third rocket in the Saturn C series studied from 1959 to 1962. The design was for a three-stage launch vehicle that could launch to low Earth orbit and send to the Moon via trans-lunar injection.
U.S. President Kennedy's proposal on May 25, 1961, of an explicit crewed lunar landing goal spurred NASA to solidify its launch vehicle requirements for a lunar landing. A week earlier, William Fleming (Office of Space Flight Programs, NASA Headquarters) chaired an ad hoc committee to conduct a six-week study of the requirements for a lunar landing. Judging the direct ascent approach to be the most feasible, they concentrated their attention accordingly, and proposed circumlunar flights in late 1965 using the Saturn C-3 launch vehicle.
In early June 1961, Bruce Lundin, deputy director of the Lewis Research Center, led a week-long study of six different rendezvous possibilities. The alternatives included Earth-orbital rendezvous (EOR), lunar-orbital rendezvous (LOR), Earth and lunar rendezvous, and rendezvous on the lunar surface, employing Saturn C-1s, C-3s, and Nova designs. Lundin's committee concluded that rendezvous enjoyed distinct advantages over direct ascent and recommended an Earth-orbital rendezvous using two or three Saturn C-3s.
NASA announced on September 7, 1961, that the government-owned Michoud Ordnance Plant near New Orleans, Louisiana, would be the site for fabrication and assembly of the Saturn C-3 first stage as well as larger vehicles in the Saturn program. Finalists were two government-owned plants in St. Louis and New Orleans. The height of the factory roof at Michoud meant that a launch vehicle with eight F-1 engines (Nova class, Saturn C-8) could not be built; four or five engines (first stage) would have to be the maximum (Saturn C-5)
This decision ended consideration of a Nova class launch vehicle for a direct ascent to the Moon or as a heavy-lift companion with the Saturn C-3 for Earth orbit rendezvous.
Lunar mission design
Direct Ascent
During various Nova's proposal, a Modular Nova concept made up of clustering the first stage of C-3 were proposed.
Earth orbit rendezvous
The Marshall Space Flight Center in Huntsville, Alabama developed an Earth orbit rendezvous proposal (EOR) for the Apollo program in 1960–1961. The proposal used a series of small rockets half the size of a Saturn V to launch different components of a spacecraft headed to the Moon. These components would be assembled in orbit around the Earth, then sent to the Moon via trans-lunar injection. In order to test and validate the feasibility of the EOR approach for the Apollo program, Project Gemini was founded with this objective: "To effect rendezvous and docking with another vehicle (Agena target vehicle), and to maneuver the combined spacecraft using the propulsion system of the target vehicle".
The Saturn C-3 was the primary launch vehicle for Earth orbit rendezvous. The booster consisted of a first stage containing two Saturn V F-1 engines, a second stage containing four powerful J-2 engines, and the S-IV stage from a Saturn I booster. Only the S-IV stage of the Saturn C-3 was developed and flown, but all of the specified engines were used on the Saturn V rocket which took men to the Moon.
Lunar orbit rendezvous
The concept of Lunar orbit rendezvous (LOR) was studied at Langley Research Center as early as 1960. John Houbolt's memorandum advocating LOR for lunar missions in November 1961 to Robert Seamans outlined the usage of the Saturn C-3 launch vehicle, and avoiding complex large boosters and lunar landers.
After six months of further discussion at NASA, in the summer of 1962, Langley Research Center's Lunar orbit rendezvous (LOR) proposal was officially selected as the mission configuration for the Apollo program on November 7, 1962. By the end of 1962, the Saturn C-3 design was deemed not necessary for Apollo program requirements as larger boosters (Saturn C-4, Saturn C-5) were then proposed, hence further work on the Saturn C-3 was cancelled.
Variants and derivatives
Since 1961, a number of variants of the Saturn C-3 have been studied, proposed, and funded. The most extensive studies focused on the Saturn C-3B variants before the end of 1962, when lunar orbit rendezvous was selected and Saturn C-5 development approved. The common theme of these variants is the first stage with at least of sea-level thrust (SL). These designs used two or three Rocketdyne F-1 engines in a S-IB-2 or S-IC stage and diameters ranging from that could lift up to to Low Earth Orbit (LEO).