Landing on the moon. Apollo 11 was the first mission to land astronauts on the moon. It blasted off on July 16, 1969, carrying three astronauts--Neil A. Armstrong, Edwin E. Aldrin, Jr., and Michael Collins.
The first two stages of a Saturn 5 rocket carried the spacecraft to an altitude of 115 miles (185 kilometers) and a speed of 15,400 miles (24,800 kilometers) per hour, just short of orbital velocity. The third stage fired briefly to accelerate the vehicle to the required speed. On the way to the moon, the crew pulled the CSM away from the Saturn rocket. They turned the CSM around and docked it to the LM, which was still attached to the Saturn. The linked vehicles then pulled free of the Saturn.
For three days, Apollo 11 coasted toward the moon. Once in lunar orbit, Armstrong and Aldrin separated the LM from the CSM. They fired the LM's descent stage and began the landing maneuver. They used the LM's rockets to slow its descent. Collins remained in the CSM. For the final touchdown, Armstrong looked out the window and selected a level landing site. Probes extended down from the LM's landing legs and signaled when the LM was about 5 feet (1.5 meters) above the surface. The engine shut off, and the LM touched down at a lowland called the Sea of Tranquility on July 20, 1969.
First Armstrong and then Aldrin crawled backward through the hatch. They descended a ladder mounted on one of the LM's legs to a wide pad at the base of the leg. A television camera mounted on the side of the LM sent blurred images of the astronauts back to the earth. Armstrong stepped off the pad onto the moon and said, "That's one small step for a man, one giant leap for mankind."
Excerpts from the "Space exploration" article, The World Book Encyclopedia © 1999