The structural efficiency of the S-II stage, in terms of the weight and pressures taken by its extra-thin walls, was comparable only to the capacity of one of nature’s most refined examples of structural efficiency, the egg.
The primary objectives of the Surveyor program, were to support the Apollo landings by: (1) developing and validating the technology for landing softly on the Moon; (2) providing data on the compatibility of the Apollo design with conditions encountered on the lunar surface; and (3) adding to the scientific knowledge of the Moon.
A total of five Lunar Orbiter missions were launched by the US in 1966 through 1967. The purpose of the lunar orbiter series was to photograph the moon’s surface for selection and verification of safe landing sites for the Surveyor and Apollo missions.
After 1957, the Soviets became accustomed to achieving “world firsts” in space accomplishments. Nevertheless, 10 years later they were not confident that they could pull off the world’s first fully automatic rendezvous and docking of two un-piloted Soyuz spacecraft. At the time the chance for success was estimated at only 50/50.