Thus the decision came down not to performance, which was clearly settled, but development risk. The Saturn had always been designed to be as low-risk as possible, the only really new components being a minor upgrade to the engine for the lower stage and the Centaur as the upper stage. Developing entirely new hydrogen-burning stages for the entire "stack" would increase the risk that a failure of any one of the components could disrupt the entire program. But as the Committee members noted: "If these propellants are to be accepted for the difficult top-stage applications, there seems to be no valid engineering reasons for not accepting the use of high-energy propellants for the less difficult application to intermediate stages." von Braun was won over; development of the current design would continue as a back-up, but the future of the Saturn was based on hydrogen and was tailored solely to NASA's requirements.