history - 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

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Over 52 years ago, in the early hours of May 5th, 1961 the US prepared to launch its first man into space. Three weeks earlier, the Soviet Union had sent Yuri Gagarin on an orbital mission. This was a suborbital mission planed to last only 15 minutes. For the moment that did not matter, the entire nation held its breath while Alan Shepard became America’s first man in space.