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.

[3] In early June 1961, Bruce Lundin, deputy director of the Lewis Research Center, led a week-long study of six different rendezvous possibilities.

[4] 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.

[6] 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.

These designs used two or three Rocketdyne F-1 engines in a S-IB-2 or S-IC stage and diameters ranging from 8 to 10 meters (26 to 33 ft) that could lift up to 110,000 pounds (50,000 kg) to Low Earth Orbit (LEO).

In the mid-1960s NASA's Marshall Space Flight Center (MSFC) initiated several studies for a launch vehicle to fill this payload capacity gap and to extend the capabilities of the Saturn family.

The Saturn II was a series of American expendable launch vehicles, studied by North American Aviation (NAA, later Rockwell) in 1966, under the NASA Marshall Space Flight Center (MSFC) and derived from components of the Saturn V rocket used for the Apollo program.

Hughes Aircraft and Boeing dusted off the earlier Saturn C-3 design and submitted their proposal for the Jarvis launch vehicle.

[10] This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.