How do astronauts get to the moon?

Answer 1

In manned missions thus far, a powerful rocket is put into a parking orbit around the earth. With Apollo, this was the S-IVB stage with the lunar lander, and command and service module (CSM) atop it. Then, all systems are checked to make sure that all systems are "go" after through ride up to orbit. Additionally, calculations are re-processed to find that little "keyhole" in space where the rocket needs to go without missing the moon, or failing to achieve the desired lunar orbit. These data are fed into the flight computers, which tell the rocket the best angle, thrust, burn time, and other flight criteria to achieve orbit around the moon at the right altitude and angles. Additional short bursts from the CSM may be needed, but we have to make sure that the CSM does not use so much fuel that it cannot return from lunar orbit once it is time to return. Then, the countdown proceeds to the trans-lunar injection (TLI) burn. The man in the left hand seat keeps his hand on the abort switch before the engines ignite, just in case something goes awry and the automatic systems do not shut it down. After this burn is found to be satisfactory, the Apollo capsule pulls away from the S-IVB stage and completes a 180 degree turn. Then, it (very) slowly approaches the Lunar Module (LM) and finally docks with it. Once docked, all systems are checked again before the CSM pulls the LM out of its location in the upper stage, and distances itself from it for safety reasons. Later in the mission, two astronauts crawl into the LM and the hatch is sealed and tested for leaks. None being found (they are in lunar orbit now), the LM will pull away and extend the lander legs ("The Eagle has wings"). The remaining part is the hairiest, as one astronaut is left behind in the CSM, and two head for a landing. During Apollo, the LM had a computer, but most of the computing was done on the ground. Not so much during landing, though. They were nearly on their own with a small computer.