Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon, and the fifth crewed mission of NASA's Apollo program. The mission was crewed by Commander Neil Armstrong, Command Module Pilot Michael Collins, and Lunar Module Pilot Edwin "Buzz" Aldrin, all of whom were on their second and final spaceflight.
Launched atop a Saturn V rocket from Kennedy Space Center in Florida on July 16 at 13:32 UTC, the Apollo spacecraft consisted of three parts: the command module (CM), which housed the three astronauts and was the only part to return to Earth; the service module (SM), which provided propulsion, electrical power, oxygen, and water to the command module; and the Lunar Module (LM), which had two stages—a descent stage with a large engine and fuel tanks for landing on the Moon, and a lighter ascent stage containing a cabin for two astronauts and a small engine to return them to lunar orbit. After a three-day transit, Armstrong and Aldrin descended to the surface aboard the LM Eagle, landing in the Sea of Tranquility (Mare Tranquillitatis) on July 20 at 20:17 UTC while Collins remained in lunar orbit aboard the CM Columbia. Armstrong became the first human to walk on the Moon approximately six hours after landing, followed by Aldrin nineteen minutes later. Together they spent around two and a half hours walking on the surface, planting an American flag, speaking by telephone with President Richard Nixon, deploying scientific instruments, and collecting 21.5 kg (47.5 lb) of lunar material. After more than 21 hours on the surface, they rejoined Collins in lunar orbit, and the crew returned safely to Earth on July 24, splashing down in the Pacific Ocean.
Apollo 11 was the culmination of the Space Race, a geopolitical competition between the United States and the Soviet Union rooted in Cold War rivalry. It fulfilled a national goal set by President John F. Kennedy in May 1961, who had challenged the United States to land a man on the Moon and return him safely before the end of the decade. The program overcame a severe setback with the fatal Apollo 1 launchpad fire in January 1967 and drew on technologies developed through the preceding Mercury and Gemini programs. The Soviet Union, despite early leads in spaceflight, was unable to match the Saturn V rocket, and its uncrewed lunar probe Luna 15 crashed on the Moon on July 21, while Neil Armstrong and Buzz Aldrin were still on the lunar surface.
Armstrong's moonwalk was broadcast live to an estimated 600 million viewers, roughly one-fifth of the world's population, making it among the most-watched television events in history. Stepping onto the lunar surface, Armstrong declared: "That's one small step for [a] man, one giant leap for mankind." Lunar samples returned by the mission led to the identification of three previously unrecognized minerals, and scientific instruments deployed on the surface continued returning data for years afterwards. The crew were honoured with ticker-tape parades, a world goodwill tour, and the Presidential Medal of Freedom. The command module Columbia is preserved at the National Air and Space Museum in Washington, D.C., while the descent stage of Eagle remains on the lunar surface.
In the late 1950s and early 1960s, the United States was engaged in the Cold War, a geopolitical rivalry with the Soviet Union. On October 4, 1957, the Soviet Union launched Sputnik 1, the first artificial satellite, surprising the world and fueling fears about Soviet technological and military capabilities. Its success demonstrated that the USSR could potentially deliver nuclear weapons over intercontinental distances, challenging American claims of military, economic, and technological superiority.
This incident sparked the Sputnik crisis and ignited the Space Race, as both superpowers sought to demonstrate superiority in spaceflight. President Dwight D. Eisenhower responded to the challenge posed by Sputnik by creating the National Aeronautics and Space Administration (NASA), and initiating Project Mercury, which aimed to place a man into Earth orbit. The Soviets took the lead on April 12, 1961, when cosmonaut Yuri Gagarin became the first person in space and the first to orbit the Earth. Nearly a month later, on May 5, 1961, Alan Shepard became the first American in space; his 15-minute flight was suborbital, not a full orbit.
Because the Soviet Union had launch vehicles with higher lift capacity, President John F. Kennedy, Eisenhower's successor, chose a challenge that exceeded the capabilities of the existing generation of rockets, so that both countries would be starting from an equal position. A crewed mission to the Moon would serve this purpose.
On May 25, 1961, Kennedy addressed the United States Congress on "Urgent National Needs" and declared:
I believe that this nation should commit itself to achieving the goal, before this decade [1960s] is out, of landing a man on the Moon and returning him safely to the Earth. No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish. We propose to accelerate the development of the appropriate lunar space craft. We propose to develop alternate liquid and solid fuel boosters, much larger than any now being developed, until certain which is superior. We propose additional funds for other engine development and for unmanned explorations—explorations which are particularly important for one purpose which this nation will never overlook: the survival of the man who first makes this daring flight. But in a very real sense, it will not be one man going to the Moon—if we make this judgment affirmatively, it will be an entire nation. For all of us must work to put him there.
On September 12, 1962, Kennedy delivered another speech before a crowd of about 40,000 people in the Rice University football stadium in Houston, Texas. A widely quoted refrain from the middle portion of the speech reads as follows:
There is no strife, no prejudice, no national conflict in outer space as yet. Its hazards are hostile to us all. Its conquest deserves the best of all mankind, and its opportunity for peaceful cooperation may never come again. But why, some say, the Moon? Why choose this as our goal? And they may well ask, why climb the highest mountain? Why, 35 years ago, fly the Atlantic? Why does Rice play Texas?
We choose to go to the Moon! We choose to go to the Moon ... We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard; because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one we intend to win, and the others, too.
In spite of that, the proposed program faced widespread opposition and was dubbed a "moondoggle" by Norbert Wiener, a mathematician at the Massachusetts Institute of Technology. The effort to land a man on the Moon already had a name: Project Apollo. When Kennedy met with Nikita Khrushchev, the Premier of the Soviet Union in June 1961, he proposed making the Moon landing a joint project, but Khrushchev declined the offer. Kennedy again proposed a joint expedition to the Moon in a speech to the United Nations General Assembly on September 20, 1963. The idea of a joint Moon mission was ultimately abandoned after Kennedy's death.
An early and crucial decision was choosing lunar orbit rendezvous over both direct ascent and Earth orbit rendezvous. A space rendezvous is an orbital maneuver in which two spacecraft navigate through space and meet up. In July 1962, NASA head James Webb announced that lunar orbit rendezvous would be used and that the Apollo spacecraft would have three major parts: a command module (CM) with a cabin for the three astronauts, and the only part that returned to Earth; a service module (SM), which supported the command module with propulsion, electrical power, oxygen, and water; and a lunar module (LM) that had two stages—a descent stage for landing on the Moon, and an ascent stage to place the astronauts back into lunar orbit. This design meant the spacecraft could be launched by a single Saturn V rocket that was then under development.