The success of Apollo 4 gave good reason to believe that the Saturn V could be trusted to propel men into space. But NASA pushed on with its plans for a second unmanned booster flight, primarily to give the Pad 39 launch team another rehearsal before sending men into deep space on the Saturn V.  The mission was called Apollo 6…

“The fire-in-the-hole abort was the most critical test of the mission and one we had to accomplish successfully prior to a manned mission.” Gene Kranz – Flight Director Apollo 5

“…our building’s shaking here. Our building’s shaking! Oh it’s terrific, the building’s shaking! This big blast window is shaking! We’re holding it with our hands! Look at that rocket go into the clouds at 3000 feet!…you can see it…you can see it…oh the roar is terrific!…”  Walter Cronkite – Apollo 4 launch.

“The S-II stage was a nightmare the minute it was conceived, and it only got worse from there. During the course of its creation, it would grind up people and careers the way the transcontinental railway devoured laborers.  Though the methods and materials used to build the S-II were reasonably well known, nobody had ever tried to apply them on such a titanic scale.  Originally, it was to be somewhere around 8 stores tall with a diameter of 22 feet, but the width ballooned from there to 27 feet before the contract was  even signed, then to 30, and finally to 33 feet.  And all the while as the size of thing increased, NASA was trimming the allowable weight.”  Harrison Storms of NAA.

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.

“It seemed that the nearby and mysterious planet was resorting to tricks to hide the secrets kept beneath its cover of clouds. As the probe drew nearer, Venus’ gravitational field increased its speed. The Doppler effect altered the wavelength of the signals received on Earth. The radio operators needed to be particularly vigilant so that the information sent from the station consistently landed in the narrow “throat” of the ground-based receivers.”  Boris Chertok

“It’s a terrible scene. Komarov burned up. All the instruments burned. We must quickly find out what prevented the main parachute from unlatching.” Chief Designer Mishin after he arrived at the Soyuz 1 crash site.