It was impossible to check out the entire spacecraft; that could only be done on the ground. In the short time available, Grifﬁn’s team ran a pre-maneuver check list, re-aligned the CSM platform, and discussed proceeding with the mission with the crew.
As Apollo 11 passed over Western Australia, at T+2 hours 26 minutes Houston relayed to Collins, Armstrong, and Aldrin – through Carnarvon – formal permission to go to the moon. “Apollo 11, this is Houston. You are go for TLI.” Mike Collins answered, “Apollo 11. Thank you.”
The success of Apollo 4 gave good reason to believe that the Saturn V could be trusted to propel men into space. But NASA pushed on with its plans for a second unmanned booster flight, primarily to give the Pad 39 launch team another rehearsal before sending men into deep space on the Saturn V. The mission was called Apollo 6…
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.