The amount of time available for operations on the Moon were limited by supplies that could be carried on the LEM; Apollo 11’s Buzz Aldrin and Neil Armstrong spent about 22 hours on the lunar surface. Once business on the Moon was wrapped up, the upper stage of the LEM would blast off, separating from descent stage, and rendezvous with the CSM (the possibility of something going wrong at this point, which might require the CSM to make unexpected maneuvers in order to make rendezvous, was one of the reasons a pilot needed to stay in orbit). Once the two spacecraft had docked, the two astronauts inside the LEM joined the pilot in the CSM, and the LEM was jettisoned, to eventually crash on the lunar surface. With all three astronauts on board, the CSM’s main engine would fire, sending the spacecraft homeward. The Apollo missions all ended with the separation of the cone-shaped Command Module from the Service Module, and the CM would re-enter the Earth’s atmosphere, with its heat shield absorbing the enormous heat of re-entry generated by atmospheric friction. Finally, the spacecraft, slowed by parachutes, would “splash down” in the ocean, with the crew and spacecraft recovered by helicopter and brought to a waiting aircraft carrier.