Apollo 11 was the spaceflight that landed the first humans on the Moon, Americans Neil Armstrong and Buzz Aldrin, on July 20, 1969, at 20:18 UTC. Armstrong became the first to step onto the lunar surface six hours later on July 21 at 02:56 UTC. Armstrong spent about two and a half hours outside the spacecraft, Aldrin slightly less, and together they collected 47.5 pounds (21.5 kg) of lunar material for return to Earth. The third member of the mission, Michael Collins, piloted the command spacecraft alone in lunar orbit until Armstrong and Aldrin returned to it just under a day later for the trip back to Earth.

Launched by a Saturn V rocket from Kennedy Space Center in Merritt Island, Florida, on July 16, Apollo 11 was the fifth manned mission of NASA's Apollo program. The Apollo spacecraft had three parts: a Command Module (CM) with a cabin for the three astronauts, and the only part that landed back on Earth; a Service Module (SM), which supported the Command Module with propulsion, electrical power, oxygen, and water; and a Lunar Module (LM) for landing on the Moon. After being sent toward the Moon by the Saturn V's upper stage, the astronauts separated the spacecraft from it and traveled for three days until they entered into lunar orbit. Armstrong and Aldrin then moved into the Lunar Module and landed in the Sea of Tranquility. They stayed a total of about 21 ¹⁄₂ hours on the lunar surface. After lifting off in the upper part of the Lunar Module and rejoining Collins in the Command Module, they returned to Earth and landed in the Pacific Ocean on July 24.

Manned Moon landings (1969–1972)

The U.S. Moon exploration program originated during the Eisenhower administration. In a series of mid-1950s articles in Collier's magazine, Wernher von Braun had popularized the idea of a manned expedition to the Moon to establish a lunar base. A manned Moon landing posed several daunting technical challenges to the U.S. and USSR. Besides guidance and weight management, atmospheric re-entry without ablative overheating was a major hurdle. After the Soviet Union's launch of Sputnik, von Braun promoted a plan for the United States Army to establish a military lunar outpost by 1965.

After the early Soviet successes, especially Yuri Gagarin's flight, U.S. President John F. Kennedy looked for a U.S. project that would capture the public imagination. He asked Vice President Lyndon Johnson to make recommendations on a scientific endeavor that would prove U.S. world leadership. The proposals included non-space options such as massive irrigation projects to benefit the Third World. The Soviets, at the time, had more powerful rockets than the United States, which gave them an advantage in some kinds of space mission.

Advances in U.S. nuclear weapons technology had led to smaller, lighter warheads, and consequently, rockets with smaller payload capacities. By comparison, Soviet nuclear weapons were much heavier, and the powerful R-7 rocket was developed to carry them. More modest potential missions such as flying around the Moon without landing or establishing a space lab in orbit (both were proposed by Kennedy to von Braun) were determined to offer too much advantage to the Soviets, since the U.S. would have to develop a heavy rocket to match the Soviets. A Moon landing, however, would capture world imagination while functioning as propaganda.

 

Mindful that the Apollo Program would economically benefit most of the key states in the next election—particularly his home state of Texas because NASA's base was in Houston—Johnson championed the Apollo program. This superficially indicated action to alleviate the fictional "missile gap" between the U.S. and USSR, a campaign promise of Kennedy's in the 1960 election. The Apollo project allowed continued development of dual-use technology.

Johnson also advised that for anything less than a lunar landing the USSR had a good chance of beating the U.S. For these reasons, Kennedy seized on Apollo as the ideal focus for U.S. efforts in space. He ensured continuing funding, shielding space spending from the 1963 tax cut and diverting money from other NASA projects. This dismayed NASA's leader, James E. Webb, who urged support for other scientific work.

The Saturn V booster was the key to U.S. Moon landings. The Saturn had a perfect record of zero failures in thirteen launches.

Whatever he said in private, Kennedy needed a different message to gain public support to uphold what he was saying and his views. Later in 1963, Kennedy asked Vice President Johnson to investigate the possible technological and scientific benefits of a Moon mission. Johnson concluded that the benefits were limited, but, with the help of scientists at NASA, he put together a powerful case, citing possible medical breakthroughs and interesting pictures of Earth from space.

For the program to succeed, its proponents would have to defeat criticism from politicians on the left, who wanted more money spent on social programs, and on those on the right, who favored a more military project. By emphasizing the scientific payoff and playing on fears of Soviet space dominance, Kennedy and Johnson managed to swing public opinion: by 1965, 58 percent of U.S. favored Apollo, up from 33 percent two years earlier. After Johnson became President in 1963, his continuing defense of the program allowed it to succeed in 1969, as Kennedy had originally hoped.

Crew

Each crewman of Apollo 11 had made a spaceflight before this mission, making it only the second all-veteran crew (the other being Apollo 10) in human spaceflight history.

Collins was originally slated to be the Command Module Pilot (CMP) on Apollo 8 but was removed when he required surgery on his back and was replaced by Jim Lovell, his backup for that flight. After Collins was medically cleared, he took what would have been Lovell's spot on Apollo 11; as a veteran of Apollo 8, Lovell was transferred to Apollo 11's backup crew, but promoted to backup commander.

Backup crew

In early 1969, Anders accepted a job with the National Space Council effective August 1969 and announced that he would retire as an astronaut on that date. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was delayed past its intended July launch (at which point Anders would be unavailable if needed) and would later join Lovell's crew and ultimately be assigned as the original Apollo 13 CMP.

Call signs

After the crew of Apollo 10 named their spacecraft Charlie Brown and Snoopy, assistant manager for public affairs Julian Scheer wrote to Manned Spacecraft Center director George M. Low to suggest the Apollo 11 crew be less flippant in naming their craft. During early mission planning, the names Snowcone and Haystack were used and put in the news release,but the crew later decided to change them.

The Command Module was named Columbia after the Columbiad, the giant cannon shell "spacecraft" fired by a giant cannon (also from Florida) in Jules Verne's 1865 novel From the Earth to the Moon. The Lunar Module was named Eagle for the national bird of the United States, the bald eagle, which is featured prominently on the mission insignia.

Insignia

 

The Apollo 11 mission insignia was designed by Collins, who wanted a symbol for "peaceful lunar landing by the United States". He chose an eagle as the symbol, put an olive branch in its beak, and drew a lunar background with the Earth in the distance. NASA officials said the talons of the eagle looked too "warlike" and after some discussion, the olive branch was moved to the claws. The crew decided the Roman numeral XI would not be understood in some nations and went with "Apollo 11"; they decided not to put their names on the patch, so it would "be representative of everyone who had worked toward a lunar landing".All colors are natural, with blue and gold borders around the patch.

When the Eisenhower dollar coin was released in 1971, the patch design provided the eagle for its reverse side.The design was also used for the smaller Susan B. Anthony dollar unveiled in 1979, ten years after the Apollo 11 mission.

Launch and flight to lunar orbit

Saturn V carrying Apollo 11 rises past the launch tower camera

Earth seen from Apollo 11 just after leaving Earth orbit (translunar injection)

In addition to throngs of people crowding highways and beaches near the launch site, millions watched the event on television, with NASA Chief of Public Information Jack King providing commentary. PresidentRichard M. Nixon viewed the proceedings from the Oval Office of the White House.

A Saturn V launched Apollo 11 from Launch Pad 39A, part of the Launch Complex 39 site at the Kennedy Space Center on July 16, 1969 at 13:32:00 UTC (9:32:00 a.m. EDT local time). It entered Earth orbit, at an altitude of 100.4 nautical miles (185.9 km) by 98.9 nautical miles (183.2 km), twelve minutes later.After one and a half orbits, the S-IVB third-stage engine pushed the spacecraft onto its trajectory toward the Moon with the trans-lunar injection (TLI) burn at 16:22:13 UTC. About 30 minutes later the command/service module pair separated from this last remaining Saturn V stage and docked with the Lunar Module still nestled in the Lunar Module Adaptor. After the Lunar Module was extracted, the combined spacecraft headed for the Moon, while the third stage booster flew on a trajectory past the Moon and into orbit around the Sun.

Landing

When Armstrong again looked outside, he saw that the computer's landing target was in a boulder-strewn area just north and east of a 300-meter (980 ft) diameter crater (later determined to be West crater, named for its location in the western part of the originally planned landing ellipse). Armstrong took semi-automatic control and, with Aldrin calling out altitude and velocity data, landed at 20:17:40 UTC on July 20 with about 25 seconds of fuel left.

Apollo 11 landed with less fuel than other missions, and the astronauts encountered a premature low fuel warning. This was later found to be the result of greater propellant 'slosh' than expected, uncovering a fuel sensor. On subsequent missions, extra anti-slosh baffles were added to the tanks to prevent this.

Throughout the descent Aldrin had called out navigation data to Armstrong, who was busy piloting the LM. A few moments before the landing, a light informed Aldrin that at least one of the 67-inch (170 cm) probes hanging from Eagle's footpads had touched the surface, and he said "Contact light!" Three seconds later, Eagle landed and Armstrong said "Shutdown." Aldrin immediately said "Okay, engine stop. ACA – out of detent." Armstrong acknowledged "Out of detent. Auto" and Aldrin continued "Mode control – both auto. Descent engine command override off. Engine arm – off. 413 is in."

Charles Duke, CAPCOM during the landing phase, acknowledged their landing by saying "We copy you down, Eagle."

Armstrong acknowledged Aldrin's completion of the post landing checklist with "Engine arm is off," before responding to Duke with the words, "Houston, Tranquility Base here. The Eagle has landed." Armstrong's unrehearsed change of call sign from "Eagle" to "Tranquility Base" emphasized to listeners that landing was complete and successful. Duke mispronounced his reply as he expressed the relief at Mission Control: "Roger, Twan— Tranquility, we copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot."

Two and a half hours after landing, before preparations began for the EVA, Aldrin radioed to Earth:

"This is the LM pilot. I'd like to take this opportunity to ask every person listening in, whoever and wherever they may be, to pause for a moment and contemplate the events of the past few hours and to give thanks in his or her own way."

He then took communion privately. At this time NASA was still fighting a lawsuit brought by atheist Madalyn Murray O'Hair (who had objected to the Apollo 8 crew reading from the Book of Genesis) demanding that their astronauts refrain from broadcasting religious activities while in space. As such, Aldrin chose to refrain from directly mentioning taking communion on the Moon. Aldrin was an elder at the Webster Presbyterian Church, and his communion kit was prepared by the pastor of the church, the Rev. Dean Woodruff. Aldrin described communion on the Moon and the involvement of his church and pastor in the October 1970 edition of Guideposts magazine and in his book Return to Earth. Webster Presbyterian possesses the chalice used on the Moon and commemorates the event each year on the Sunday closest to July 20.

The astronauts planned placement of the Early Apollo Scientific Experiment Package (EASEP) and the U.S. flag by studying their landing site through Eagle's twin triangular windows, which gave them a 60° field of view. Preparation required longer than the two hours scheduled. Armstrong initially had some difficulties squeezing through the hatch with his Portable Life Support System (PLSS). According to veteran Moon-walker John Young, a redesign of the LM to incorporate a smaller hatch had not been followed by a redesign of the PLSS backpack, so some of the highest heart rates recorded from Apollo astronauts occurred during LM egress and ingress.

At 02:39 UTC on Monday July 21, 1969, Armstrong opened the hatch, and at 02:51 UTC began his descent to the lunar surface. The Remote Control Unit controls on his chest kept him from seeing his feet. Climbing down the nine-rung ladder, Armstrong pulled a D-ring to deploy the Modular Equipment Stowage Assembly (MESA) folded against Eagle's side and activate the TV camera, and at 02:56:15 UTC he set his left foot on the surface. The first landing used slow-scan television incompatible with commercial TV, so it was displayed on a special monitor and a conventional TV camera viewed this monitor, significantly reducing the quality of the picture.The signal was received at Goldstone in the United States but with better fidelity by Honeysuckle Creek Tracking Station in Australia. Minutes later the feed was switched to the more sensitive Parkes radio telescope in Australia. Despite some technical and weather difficulties, ghostly black and white images of the first lunar EVA were received and broadcast to at least 600 million people on Earth.Although copies of this video in broadcast format were saved and are widely available, recordings of the original slow scan source transmission from the lunar surface were accidentally destroyed during routine magnetic tape re-use at NASA.

While still on the ladder, Armstrong uncovered a plaque mounted on the LM Descent Stage bearing two drawings of Earth (of the Western and Eastern Hemispheres), an inscription, and signatures of the astronauts and President Nixon. The inscription read:

Here men from the planet Earth first set foot upon the Moon, July 1969 A.D. We came in peace for all mankind.

After describing the surface dust as "very fine-grained" and "almost like a powder,"Armstrong stepped off Eagle's footpad and uttered his famous line, "That's one small step for [a] man, one giant leap for mankind" six and a half hours after landing.Aldrin joined him, describing the view as "Magnificent desolation."

In addition to fulfilling President Kennedy's mandate to land a man on the Moon before the end of the 1960s, Apollo 11 was an engineering test of the Apollo system; therefore, Armstrong snapped photos of the LM so engineers would be able to judge its post-landing condition. He removed the TV camera from the MESA and made a panoramic sweep, then mounted it on a tripod 68 feet (21 m) from the LM. The TV camera cable remained partly coiled and presented a tripping hazard throughout the EVA.

Armstrong said that moving in the lunar gravity, one-sixth of Earth's, was "even perhaps easier than the simulations ... It's absolutely no trouble to walk around."Aldrin joined him on the surface and tested methods for moving around, including two-footed kangaroo hops. The PLSS backpack created a tendency to tip backwards, but neither astronaut had serious problems maintaining balance. Loping became the preferred method of movement. The astronauts reported that they needed to plan their movements six or seven steps ahead. The fine soil was quite slippery. Aldrin remarked that moving from sunlight into Eagle's shadow produced no temperature change inside the suit, though the helmet was warmer in sunlight, so he felt cooler in shadow.

The astronauts planted a specially designed U.S. flag on the lunar surface, in clear view of the TV camera. Some time later, President Richard Nixon spoke to them through a telephone-radio transmission which Nixon called "the most historic phone call ever made from the White House." Nixon originally had a long speech prepared to read during the phone call, but Frank Borman, who was at the White House as a NASA liaison during Apollo 11, convinced Nixon to keep his words brief, to respect the lunar landing as Kennedy's legacy.Armstrong thanked the President, and gave a brief reflection on the significance of the moment.