Page 163 - MY STORY

Stack Assembly
Even if we considered clustering the main Saturn V
engines, there was no easy way to assemble this

monstrosity on earth and launch it. Just too big. The
obvious answer from NASA and our engineers was to
launch separate elements into low earth orbit and

assemble all components in space. We and the Soviets
had already worked to assemble stuff in space, and
although challenging, this was considered as readily

doable. This approach was used on the future
International Space Station and it worked admirably. We

could also fuel the necessary propulsion stages in space in
order to lower launch weight and complexity.

Propulsion System from Earth to Mars and Back

NASA had already started the Nuclear Engine for Rocket
Vehicle Application (NERVA) in the 1960’s. By the early

70’s they had demonstrated that NERVA worked and
worked well. The whole idea of NERVA was to at least
double the propulsion efficiency of existing liquid

hydrogen/oxygen systems used for Apollo, be able to run
for hours (instead of minutes), and be able to throttle the
engines from zero to full thrust multiple times.