Launch vehicle The Saturn V (AS-504) used on Apollo9 was the fourth to be flown, the second to carry astronauts to space, and the first to bear a lunar module. Although similar in configuration to the SaturnV used on Apollo 8, several changes were made. The inner core of the F-1 engine chamber in the first (S-IC) stage was removed, thus saving weight and allowing for a slight increase in specific impulse. Weight was also saved by replacing the skins of the liquid oxygen tanks with lighter ones, and by providing lighter versions of other components. Efficiency was increased in the S-II second stage with uprated J-2 engines, and through a closed-loop propellant utilization system rather than Apollo 8's open-loop system. Of the weight reduction in the second stage, about half came from a 16 percent reduction in the thickness of the tank side walls.
launch vehicle the saturn v (as-504) used on apollo9 was the fourth to be flown the second to carry astronauts to space and the first to bear a lunar module although similar in configuration to the saturnv used on apollo 8 several changes were made the inner core of the f-1 engine chamber in the first (s-ic) stage was removed thus saving weight and allowing for a slight increase in specific impulse weight was also saved by replacing the skins of the liquid oxygen tanks with lighter ones and by providing lighter versions of other components efficiency was increased in the s-ii second stage with uprated j-2 engines and through a closed-loop propellant utilization system rather than apollo 8's open-loop system of the weight reduction in the second stage about half came from a 16 percent reduction in the thickness of the tank side walls