J-2 - Space Rocket History Podcast

The key to high-energy stages was to use liquid hydrogen as the fuel. Liquid hydrogen fuel appealed to rocket designers because of its high specific impulse, which is a basic measure of rocket performance. Specific Impulse is the impulse delivered per unit of propellant consumed. You might think of it as the efficiency of the rocket. Compared to an RP-1 (kerosene) fueled engine of similar size, liquid hydrogen fuel could increase the specific impulse or efficiency of an engine by 40 percent. The combination of hydrogen and oxygen for propellants made the moon shot feasible.

S-IV Rocket Stage

S-IV & S-IVB Stage Position

S-IV Stage in Saturn IB and V

S-IVB Differences Between Saturn IB and V

Podcast: Play in new window | Download

Subscribe: Email | TuneIn | RSS

Max Faget’s position was that considering the difficulty of the job, if each mission was successful half the time, it would be well worth the effort. But Gilruth thought that was too low. He want a 90% mission success ratio and a 99% ratio for Astronaut safety. Walt Williams who was currently running the Mercury program believed that astronaut safety needed to be limited to only 1 failure in a million which was 99.9999%.