Max Faget thought the first stage of the moon rocket should use four solid-fueled engines, 6.6 meters in diameter. He reasoned these could certainly accomplish whatever mission was required of either the Saturn or Nova, and it would be more cost effective. Faget said it made good sense to use cheap solid fuels for expendable rockets and more expensive liquid fuels for reusable engines. Faget called the individual solid rocket ‘the Tiger.’
The success of Gus Grissom and John Young’s Gemini 3 flight paved the way for long duration space missions. The longest U.S. manned space flight to date was Gordon Cooper’s 34 hour Mercury flight. The Soviets, however, had four long duration flights to their credit, ranging from 70 to 119 hours. It was time for the US to attempt a long duration flight.