Apollo 11 Moon Landing

United States #C76 (1969)
United States #C76 (1969)

On July 20, 1969, Apollo 11 mission commander Neil Armstrong and pilot Buzz Aldrin landed the lunar module Eagle on the Moon at 20:18 UTC. Armstrong became the first human in history to step onto the lunar surface six hours later on July 21 at 02:56:15 UTC; Aldrin joined him about 20 minutes later. They spent about two and a quarter hours together outside the spacecraft, and collected 47.5 pounds (21.5 kg) of lunar material to bring back to Earth. Michael Collins piloted the command module Columbia alone in lunar orbit while they were on the Moon’s surface. Armstrong and Aldrin spent just under a day on the lunar surface before rendezvousing with Columbia in lunar orbit.

Apollo 11 was launched by a Saturn V rocket from Kennedy Space Center in Merritt Island, Florida, on July 16, and 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) that had two stages — a lower stage for landing on the Moon, and an upper stage to place the astronauts back into lunar orbit. 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 Eagle and landed in the Sea of Tranquility. They stayed a total of about 21.5 hours on the lunar surface. The astronauts used Eagle’s upper stage to lift off from the lunar surface and rejoin Collins in the command module. They jettisoned Eagle before they performed the maneuvers that blasted them out of lunar orbit on a trajectory back to Earth. They returned to Earth and landed in the Pacific Ocean on July 24, 1969.

Broadcast on live TV to a worldwide audience, Armstrong stepped onto the lunar surface and described the event as “one small step for [a] man, one giant leap for mankind.” Apollo 11 effectively ended the Space Race and fulfilled a national goal proposed in 1961 by U.S. President John F. Kennedy: “before this decade is out, of landing a man on the Moon and returning him safely to the Earth.”

To date, the United States is the only country to have successfully conducted manned missions to the Moon. There have been six manned U.S. landings and numerous unmanned landings. A total of twelve men have landed on the Moon. This was accomplished with two U.S. pilot-astronauts flying a lunar module on each of six NASA missions across a 41-month period starting on July 20, 1969, and ending on December 14, 1972, Gene Cernan and Jack Schmitt on Apollo 17. Cernan was the last to step off the lunar surface. All Apollo lunar missions had a third crew member who remained on board the Command Module. The last three missions had a rover for increased mobility.

The Apollo program, also known as Project Apollo, was the third United States human spaceflight program carried out by the National Aeronautics and Space Administration (NASA), First conceived during Dwight D. Eisenhower’s administration as a three-man spacecraft to follow the one-man Project Mercury which put the first Americans in space, Apollo was later dedicated to President John F. Kennedy’s national goal of “landing a man on the Moon and returning him safely to the Earth” by the end of the 1960s, which he proposed in an address to Congress on May 25, 1961.

National Geographic Moon map, 2003 edition

In November 1960, John F. Kennedy was elected president after a campaign that promised American superiority over the Soviet Union in the fields of space exploration and missile defense. Up to the election of 1960, Kennedy had been speaking out against the “missile gap” that he and many other senators felt had formed between the Soviets and themselves due to the inaction of President Eisenhower. Beyond military power, Kennedy used aerospace technology as a symbol of national prestige, pledging to make the US not “first but, first and, first if, but first period.” Despite Kennedy’s rhetoric, he did not immediately come to a decision on the status of the Apollo program once he became president. He knew little about the technical details of the space program, and was put off by the massive financial commitment required by a manned Moon landing. When Kennedy’s newly appointed NASA Administrator James E. Webb requested a 30 percent budget increase for his agency, Kennedy supported an acceleration of NASA’s large booster program but deferred a decision on the broader issue.

On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first person to fly in space, reinforcing American fears about being left behind in a technological competition with the Soviet Union. At a meeting of the US House Committee on Science and Astronautics one day after Gagarin’s flight, many congressmen pledged their support for a crash program aimed at ensuring that America would catch up. Kennedy was circumspect in his response to the news, refusing to make a commitment on America’s response to the Soviets.

On April 20, Kennedy sent a memo to Vice President Lyndon B. Johnson, asking Johnson to look into the status of America’s space program, and into programs that could offer NASA the opportunity to catch up. Johnson responded approximately one week later, concluding that “we are neither making maximum effort nor achieving results necessary if this country is to reach a position of leadership.” His memo concluded that a manned Moon landing was far enough in the future that it was likely the United States would achieve it first.

On May 25, 1961, twenty days after the first US manned spaceflight Freedom 7, Kennedy proposed the manned Moon landing in a Special Message to the Congress on Urgent National Needs:

Now it is time to take longer strides – time for a great new American enterprise – time for this nation to take a clearly leading role in space achievement, which in many ways may hold the key to our future on Earth.

…I believe that this nation should commit itself to achieving the goal, before this decade 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 in the long-range exploration of space; and none will be so difficult or expensive to accomplish.

At the time of Kennedy’s proposal, only one American had flown in space — less than a month earlier — and NASA had not yet sent an astronaut into orbit. Even some NASA employees doubted whether Kennedy’s ambitious goal could be met. By 1963, Kennedy even came close to agreeing to a joint US-USSR Moon mission, to eliminate duplication of effort.

With the clear goal of a manned landing replacing the more nebulous goals of space stations and cislunar flights, NASA had to hit the ground running, and decided to discard the feasibility study designs of Convair, GE, and Martin, and proceed with Faget’s command / service module design. The mission module was determined to be only useful as an extra room, and therefore deemed unnecessary. They used Faget’s design as the specification for another competition for spacecraft procurement bids in October 1961. On November 28, 1961, it was announced that North American Aviation had won the contract, although its bid was not rated as good as Martin’s. Webb, Dryden and Robert Seamans chose it in preference due to North American’s longer association with NACA.

Landing men on the Moon by the end of 1969 required the most sudden burst of technological creativity, and the largest commitment of resources ($24 billion) ever made by any nation in peacetime. At its peak, the Apollo program employed 400,000 people and required the support of over 20,000 industrial firms and universities.

On July 1, 1960, NASA established the Marshall Space Flight Center (MSFC) in Huntsville, Alabama. MSFC designed the heavy lift-class Saturn launch vehicles, which would be required for Apollo.

Faget’s preliminary Apollo design employed a cone-shaped command module, supported by one of several service modules providing propulsion and electrical power, sized appropriately for the space station, cislunar, and lunar landing missions. Once Kennedy’s Moon landing goal became official, detailed design began of a Command/Service Module (CSM) in which the crew would spend the entire direct-ascent mission and lift off from the lunar surface for the return trip, after being soft-landed by a larger landing propulsion module. The final choice of lunar orbit rendezvous changed the CSM’s role to the translunar ferry used to transport the crew, along with a new spacecraft, the Lunar Excursion Module (LEM, later shortened to Lunar Module, LM) which would take two men to the lunar surface and return them to the CSM.

The Command Module (CM) was the conical crew cabin, designed to carry three astronauts from launch to lunar orbit and back to an Earth ocean landing. It was the only component of the Apollo spacecraft to survive without major configuration changes as the program evolved from the early Apollo study designs. Its exterior was covered with an ablative heat shield, and had its own reaction control system (RCS) engines to control its attitude and steer its atmospheric entry path. Parachutes were carried to slow its descent to splashdown. The module was 11.42 feet (3.48 m) tall, 12.83 feet (3.91 m) in diameter, and weighed approximately 12,250 pounds (5,560 kg).

A cylindrical Service Module (SM) supported the Command Module, with a service propulsion engine and an RCS with propellants, and a fuel cell power generation system with liquid hydrogen and liquid oxygen reactants. A high-gain S-band antenna was used for long-distance communications on the lunar flights. On the extended lunar missions, an orbital scientific instrument package was carried. The Service Module was discarded just before re-entry. The module was 24.6 feet (7.5 m) long and 12.83 feet (3.91 m) in diameter. The initial lunar flight version weighed approximately 51,300 pounds (23,300 kg) fully fueled, while a later version designed to carry a lunar orbit scientific instrument package weighed just over 54,000 pounds (24,000 kg).

North American Aviation won the contract to build the CSM, and also the second stage of the Saturn V launch vehicle for NASA. Because the CSM design was started early before the selection of lunar orbit rendezvous, the service propulsion engine was sized to lift the CSM off of the Moon, and thus was oversized to about twice the thrust required for translunar flight. Also, there was no provision for docking with the Lunar Module. A 1964 program definition study concluded that the initial design should be continued as Block I which would be used for early testing, while Block II, the actual lunar spacecraft, would incorporate the docking equipment and take advantage of the lessons learned in Block I development.

The Lunar Module (LM) was designed to descend from lunar orbit to land two astronauts on the Moon and take them back to orbit to rendezvous with the Command Module. Not designed to fly through the Earth’s atmosphere or return to Earth, its fuselage was designed totally without aerodynamic considerations, and was of an extremely lightweight construction. It consisted of separate descent and ascent stages, each with its own engine. The descent stage contained storage for the descent propellant, surface stay consumables, and surface exploration equipment. The ascent stage contained the crew cabin, ascent propellant, and a reaction control system. The initial LM model weighed approximately 33,300 pounds (15,100 kg), and allowed surface stays up to around 34 hours. An Extended Lunar Module weighed over 36,200 pounds (16,400 kg), and allowed surface stays of over 3 days. The contract for design and construction of the Lunar Module was awarded to Grumman Aircraft Engineering Corporation, and the project was overseen by Thomas J. Kelly.

Before the Apollo program began, Wernher von Braun and his team of rocket engineers had started work on plans for very large launch vehicles, the Saturn series, and the even larger Nova series. In the midst of these plans, von Braun was transferred from the Army to NASA, and made Director of the Marshall Space Flight Center. The initial direct ascent plan to send the three-man Apollo Command/Service Module directly to the lunar surface, on top of a large descent rocket stage, would require a Nova-class launcher, with a lunar payload capability of over 180,000 pounds (82,000 kg). The June 11, 1962, decision to use lunar orbit rendezvous enabled the Saturn V to replace the Nova, and the MSFC proceeded to develop the Saturn rocket family for Apollo.

Saturn V launch vehicles and flights were designated with an AS-500 series number, “AS” indicating “Apollo Saturn” and the “5” indicating Saturn V. The three-stage Saturn V was designed to send a fully fueled CSM and LM to the Moon. It was 33 feet (10.1 m) in diameter and stood 363 feet (110.6 m) tall with its 96,800-pound (43,900 kg) lunar payload. Its capability grew to 103,600 pounds (47,000 kg) for the later advanced lunar landings. The S-IC first stage burned RP-1/LOX for a rated thrust of 7,500,000 pounds-force (33,400 kN), which was upgraded to 7,610,000 pounds-force (33,900 kN). The second and third stages burned liquid hydrogen, and the third stage was a modified version of the S-IVB, with thrust increased to 230,000 pounds-force (1,020 kN) and capability to restart the engine for translunar injection after reaching a parking orbit.

Apollo 11 was the second all-veteran multi-person crew (the first being Apollo 10) in human spaceflight history. A previous solo veteran flight had been made on Soyuz 1 in 1967 by Soviet cosmonaut Vladimir Komarov. Michael 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 and promoted to backup commander. Apollo 11 was the second spaceflight for each of the three astronauts: Commander Neil A. Armstrong, Command Module Pilot Michael Collins, and Lunar Module Pilot Edwin “Buzz” E. Aldrin, Jr.

Left to right: Armstrong, Collins, Aldrin
Left to right: Armstrong, Collins, Aldrin

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 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.

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.

Neil Armstrong’s personal preference kit carried a piece of wood from the Wright brothers’ 1903 airplane’s left propeller and a piece of fabric from its wing, along with a diamond-studded astronaut pin originally given to Deke Slayton by the widows of the Apollo 1 crew. This pin had been intended to be flown on Apollo 1 and given to Slayton after the mission but following the disastrous launch pad fire and subsequent funerals, the widows gave the pin to Slayton and Armstrong took it on Apollo 11.

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). In addition to many 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. President Richard M. Nixon viewed the proceedings from the Oval Office of the White House.

The spacecraft entered Earth orbit, at an altitude of 100.4 nautical miles (185.9 km) by 98.9 nautical miles (183.2 km), twelve minutes after its launch. 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 transposition, docking, and extraction maneuver was performed: this involved separating the Apollo Command/Service Module (CSM) from the spent rocket stage, turning around, and docking with the Lunar Module still attached to the stage. After the Lunar Module was extracted, the combined spacecraft headed for the Moon, while the rocket stage flew on a trajectory past the Moon and into orbit around the Sun.

 

On July 19 at 17:21:50 UTC, Apollo 11 passed behind the Moon and fired its service propulsion engine to enter lunar orbit. In the thirty orbits that followed, the crew saw passing views of their landing site in the southern Sea of Tranquility (Mare Tranquillitatis) about 12 miles (19 km) southwest of the crater Sabine D (0.67408N, 23.47297E). The landing site was selected in part because it had been characterized as relatively flat and smooth by the automated Ranger 8 and Surveyor 5 landers along with the Lunar Orbiter mapping spacecraft and unlikely to present major landing or extravehicular activity (EVA) challenges.

On July 20, 1969, the Lunar Module Eagle separated from the Command Module Columbia. Collins, alone aboard Columbia, inspected Eagle as it pirouetted before him to ensure the craft was not damaged. As the descent began, Armstrong and Aldrin found that they were passing landmarks on the surface four seconds early and reported that they were “long”; they would land miles west of their target point.

Five minutes into the descent burn, and 6,000 feet (1,800 m) above the surface of the Moon, the LM navigation and guidance computer distracted the crew with the first of several unexpected “1202” and “1201” program alarms. Inside Mission Control Center in Houston, Texas, computer engineer Jack Garman told guidance officer Steve Bales it was safe to continue the descent, and this was relayed to the crew. The program alarms indicated “executive overflows”, meaning the guidance computer could not complete all of its tasks in real time and had to postpone some of them.

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 980-foot (300-meter) 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 Sunday July 20, 1969, 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 schedule for the mission called for the astronauts to follow the landing with a five-hour sleep period as they had been awake since early morning. However, they elected to forgo the sleep period and begin the preparations for the EVA early, thinking that they would be unable to sleep.

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,” six and a half hours after landing, Armstrong stepped off Eagle’s footpad and declared, “That’s one small step for [a] man, one giant leap for mankind.”

Armstrong intended to say “That’s one small step for a man”, but the word “a” is not audible in the transmission, and thus was not initially reported by most observers of the live broadcast. When later asked about his quote, Armstrong said he believed he said “for a man”, and subsequent printed versions of the quote included the “a” in square brackets. One explanation for the absence may be that his accent caused him to slur the words “for a” together; another is the intermittent nature of the audio and video links to Earth, partly because of storms near Parkes Observatory. More recent digital analysis of the tape claims to reveal the “a” may have been spoken but obscured by static.

About seven minutes after stepping onto the Moon’s surface, Armstrong collected a contingency soil sample using a sample bag on a stick. He then folded the bag and tucked it into a pocket on his right thigh. This was to guarantee there would be some lunar soil brought back in case an emergency required the astronauts to abandon the EVA and return to the LM.

Twelve minutes after the contingency sample was collected, Aldrin joined Armstrong on the surface, and described the view with the simple phrase, “Magnificent desolation.”

Aldrin poses on the Moon, allowing Armstrong to photograph both of them using the visor's reflection
Aldrin poses on the Moon, allowing Armstrong to photograph both of them using the visor’s reflection

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:

Nixon: Hello, Neil and Buzz. I’m talking to you by telephone from the Oval Room at the White House. And this certainly has to be the most historic telephone call ever made. I just can’t tell you how proud we all are of what you’ve done. For every American, this has to be the proudest day of our lives. And for people all over the world, I am sure they too join with Americans in recognizing what an immense feat this is. Because of what you have done, the heavens have become a part of man’s world. And as you talk to us from the Sea of Tranquility, it inspires us to redouble our efforts to bring peace and tranquility to Earth. For one priceless moment in the whole history of man, all the people on this Earth are truly one: one in their pride in what you have done, and one in our prayers that you will return safely to Earth.

Armstrong: Thank you, Mr. President. It’s a great honor and privilege for us to be here, representing not only the United States, but men of peace of all nations, and with interest and curiosity, and men with a vision for the future. It’s an honor for us to be able to participate here today.

The MESA failed to provide a stable work platform and was in shadow, slowing work somewhat. As they worked, the moonwalkers kicked up gray dust which soiled the outer part of their suits, the integrated thermal meteoroid garment.

Apollo 11 Lunar Module Pilot Buzz Aldrin's bootprint. Aldrin photographed this bootprint about an hour into their lunar extra-vehicular activity on July 20, 1969, as part of investigations into the soil mechanics of the lunar surface. This photo would later become synonymous with humankind's venture into space.
Apollo 11 Lunar Module Pilot Buzz Aldrin’s bootprint. Aldrin photographed this bootprint about an hour into their lunar extra-vehicular activity on July 20, 1969, as part of investigations into the soil mechanics of the lunar surface. This photo would later become synonymous with humankind’s venture into space.

They deployed the EASEP, which included a passive seismograph and a Lunar Ranging Retroreflector (LRRR). Then Armstrong walked 196 feet (60 m) from the LM to snap photos at the rim of Little West Crater while Aldrin collected two core tubes. He used the geological hammer to pound in the tubes — the only time the hammer was used on Apollo 11. The astronauts then collected rock samples using scoops and tongs on extension handles. Many of the surface activities took longer than expected, so they had to stop documenting sample collection halfway through the allotted 34 minutes.

Three new minerals were discovered in the rock samples collected by the astronauts: armalcolite, tranquillityite, and pyroxferroite. Armalcolite was named after Armstrong, Aldrin, and Collins.

During this period, Mission Control used a coded phrase to warn Armstrong that his metabolic rates were high and that he should slow down. He was moving rapidly from task to task as time ran out. However, as metabolic rates remained generally lower than expected for both astronauts throughout the walk, Mission Control granted the astronauts a 15-minute extension. In a 2010 interview, Armstrong, who had walked a maximum of 196 feet (60 m) from the LM, explained that NASA limited the first moonwalk’s time and distance because there was no empirical proof of how much cooling water the astronauts’ PLSS backpacks would consume to handle their body heat generation while working on the Moon.

Aldrin entered Eagle first. With some difficulty the astronauts lifted film and two sample boxes containing 47.5 pounds (21.55 kg) of lunar surface material to the LM hatch using a flat cable pulley device called the Lunar Equipment Conveyor. Armstrong reminded Aldrin of a bag of memorial items in his suit pocket sleeve, and Aldrin tossed the bag down; Armstrong then jumped to the ladder’s third rung and climbed into the LM. After transferring to LM life support, the explorers lightened the ascent stage for return to lunar orbit by tossing out their PLSS backpacks, lunar overshoes, one Hasselblad camera, and other equipment. They then pressurized the LM and settled down to sleep.

President Nixon’s speech writer William Safire had prepared “In Event of Moon Disaster” for the President to read on television in the event the Apollo 11 astronauts were stranded on the Moon. The contingency plan originated in a memo from Safire to Nixon’s White House Chief of Staff H. R. Haldeman, in which Safire suggested a protocol the administration might follow in reaction to such a disaster. According to the plan, Mission Control would “close down communications” with the LM, and a clergyman would “commend their souls to the deepest of the deep” in a public ritual likened to burial at sea. The last line of the prepared text contained an allusion to Rupert Brooke’s First World War poem, “The Soldier”. The plan included presidential telephone calls to the astronauts’ wives.

While moving within the cabin, Aldrin accidentally damaged the circuit breaker that would arm the main engine for lift off from the Moon. There was concern this would prevent firing the engine, stranding them on the Moon. Fortunately, a felt-tip pen was sufficient to activate the switch. Had this not worked, the lunar module circuitry could have been reconfigured to allow firing the ascent engine.

After about seven hours of rest, the crew was awakened by Houston to prepare for the return flight. Two and a half hours later, at 17:54 UTC, they lifted off in Eagle’s ascent stage to rejoin Collins aboard Columbia in lunar orbit.

A view of the Apollo 11 lunar module Eagle as it returned from the surface of the moon to dock with the command module Columbia. A smooth mare area is visible on the Moon below and a half-illuminated Earth hangs over the horizon. The lunar module ascent stage was about 4 meters across. Command module pilot Michael Collins took this picture just before docking at 21:34:00 UT (5:34 p.m. EDT) 21 July 1969. (Apollo 11, AS11-44-6642)
A view of the Apollo 11 lunar module Eagle as it returned from the surface of the moon to dock with the command module Columbia. A smooth mare area is visible on the Moon below and a half-illuminated Earth hangs over the horizon. The lunar module ascent stage was about 4 meters across. Command module pilot Michael Collins took this picture just before docking at 21:34:00 UT (5:34 p.m. EDT) 21 July 1969. (Apollo 11, AS11-44-6642)

After more than 21½ total hours on the lunar surface, they had left behind scientific instruments that included a retroreflector array used for the Lunar Laser Ranging Experiment and a Passive Seismic Experiment Package used to measure moonquakes. They also left an Apollo 1 mission patch, and a memorial bag containing a gold replica of an olive branch as a traditional symbol of peace and a silicon message disk. The disk carries the goodwill statements by Presidents Eisenhower, Kennedy, Johnson, and Nixon and messages from leaders of 73 countries around the world. The disc also carries a listing of the leadership of the US Congress, a listing of members of the four committees of the House and Senate responsible for the NASA legislation, and the names of NASA’s past and present top management. In his 1989 book, Men from Earth, Aldrin says that the items included Soviet medals commemorating Cosmonauts Vladimir Komarov and Yuri Gagarin. Also, according to Deke Slayton’s book Moonshot, Armstrong carried with him a special diamond-studded astronaut pin from Slayton.

Film taken from the LM Ascent Stage upon liftoff from the Moon reveals the American flag, planted some 25 feet (8 m) from the descent stage, whipping violently in the exhaust of the ascent stage engine. Aldrin looked up in time to witness the flag topple: “The ascent stage of the LM separated … I was concentrating on the computers, and Neil was studying the attitude indicator, but I looked up long enough to see the flag fall over.” Subsequent Apollo missions usually planted the American flags at least 100 feet (30 m) from the LM to prevent them being blown over by the ascent engine exhaust.

After rendezvous with Columbia, Eagle‘s ascent stage was jettisoned into lunar orbit on July 21, 1969, at 23:41 UTC. Just before the Apollo 12 flight, it was noted that Eagle was still likely to be orbiting the Moon. Later NASA reports mentioned that Eagle‘s orbit had decayed, resulting in it impacting in an “uncertain location” on the lunar surface. The location is uncertain because the Eagle ascent stage was not tracked after it was jettisoned, and the lunar gravity field is sufficiently non-uniform to make the orbit of the spacecraft unpredictable after a short time. NASA estimated that the orbit had decayed within months and would have impacted on the Moon.

On July 23, the last night before splashdown, the three astronauts made a television broadcast in which Collins commented:

… The Saturn V rocket which put us in orbit is an incredibly complicated piece of machinery, every piece of which worked flawlessly … We have always had confidence that this equipment will work properly. All this is possible only through the blood, sweat, and tears of a number of a people … All you see is the three of us, but beneath the surface are thousands and thousands of others, and to all of those, I would like to say, “Thank you very much.”

Aldrin added:

This has been far more than three men on a mission to the Moon; more, still, than the efforts of a government and industry team; more, even, than the efforts of one nation. We feel that this stands as a symbol of the insatiable curiosity of all mankind to explore the unknown … Personally, in reflecting on the events of the past several days, a verse from Psalms comes to mind. “When I consider the heavens, the work of Thy fingers, the Moon and the stars, which Thou hast ordained; What is man that Thou art mindful of him?”

Armstrong concluded:

The responsibility for this flight lies first with history and with the giants of science who have preceded this effort; next with the American people, who have, through their will, indicated their desire; next with four administrations and their Congresses, for implementing that will; and then, with the agency and industry teams that built our spacecraft, the Saturn, the Columbia, the Eagle, and the little EMU, the spacesuit and backpack that was our small spacecraft out on the lunar surface. We would like to give special thanks to all those Americans who built the spacecraft; who did the construction, design, the tests, and put their hearts and all their abilities into those craft. To those people tonight, we give a special thank you, and to all the other people that are listening and watching tonight, God bless you. Good night from Apollo 11.

On the return to Earth, a bearing at the Guam tracking station failed, potentially preventing communication on the last segment of the Earth return. A regular repair was not possible in the available time but the station director, Charles Force, had his ten-year-old son Greg use his small hands to reach into the housing and pack it with grease. Greg later was thanked by Armstrong.

On July 24, the astronauts returned home aboard the Command Module Columbia just before dawn local time (16:51 UTC) at 13°19′N 169°9′W, in the Pacific Ocean 1,440 nautical miles (2,660 km) east of Wake Island, 210 nautical miles (380 km) south of Johnston Atoll, and 13 nautical miles (24 km) from the recovery ship, USS Hornet.

At 16:44 UTC the drogue parachutes had been deployed and seven minutes later the Command Module struck the water forcefully. During splashdown, the Command Module landed upside down but was righted within 10 minutes by flotation bags triggered by the astronauts. “Everything’s okay. Our checklist is complete. Awaiting swimmers”, was Armstrong’s last official transmission from the Columbia. A diver from the Navy helicopter hovering above attached a sea anchor to the Command Module to prevent it from drifting. Additional divers attached flotation collars to stabilize the module and position rafts for astronaut extraction.

Though the chance of bringing back pathogens from the lunar surface was considered remote, it was considered a possibility and NASA took great precautions at the recovery site. Divers provided the astronauts with Biological Isolation Garments (BIGs) which were worn until they reached isolation facilities on board the Hornet. Additionally, astronauts were rubbed down with a sodium hypochlorite solution and the Command Module wiped with Betadine to remove any lunar dust that might be present. The raft containing decontamination materials was then intentionally sunk.

A second Sea King helicopter hoisted the astronauts aboard one by one, where a NASA flight surgeon gave each a brief physical check during the 0.5 nautical miles (930 m) trip back to the Hornet.

After touchdown on the Hornet, the astronauts exited the helicopter, leaving the flight surgeon and three crewmen. The helicopter was then lowered into hangar bay #2 where the astronauts walked the 30 feet (9.1 m) to the Mobile Quarantine Facility (MQF) where they would begin their 21 days of quarantine. This practice would continue for two more Apollo missions, Apollo 12 and Apollo 14, before the Moon was proven to be barren of life and the quarantine process dropped.

President Richard Nixon was aboard Hornet to personally welcome the astronauts back to Earth. He told the astronauts, “As a result of what you’ve done, the world has never been closer together before.” After Nixon departed, the Hornet was brought alongside the five-ton Command Module where it was placed aboard by the ship’s crane, placed on a dolly and moved next to the MQF. The Hornet sailed for Pearl Harbor where the Command Module and MQF were airlifted to the Manned Spacecraft Center.

In accordance with the recently passed Extra-Terrestrial Exposure Law, the astronauts were placed in quarantine for fear that the Moon might contain undiscovered pathogens and that the astronauts might have been exposed to them during their Moon walks. However, after almost three weeks in confinement (first in their trailer and later in the Lunar Receiving Laboratory at the Manned Spacecraft Center), the astronauts were given a clean bill of health. On August 10, 1969, the astronauts exited quarantine.

On August 13, they rode in parades in their honor in New York, Chicago, and Los Angeles. On the same evening in Los Angeles there was an official State Dinner to celebrate the flight, attended by members of Congress, 44 governors, the Chief Justice of the United States, and ambassadors from 83 nations at the Century Plaza Hotel. President Richard Nixon and Vice President Spiro T. Agnew honored each astronaut with a presentation of the Presidential Medal of Freedom. This celebration was the beginning of a 45-day “Giant Leap” tour that brought the astronauts to 25 foreign countries and included visits with prominent leaders such as Queen Elizabeth II of the United Kingdom. Many nations honored the first manned Moon landing with special features in magazines or by issuing Apollo 11 commemorative postage stamps or coins.

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On September 9, 1969, The United States Post Office Department released a single 10-cent Air Mail stamp designed by Paul Calle to mark the Apollo 11 moon landing and Neil Armstrong’s accomplishment as the first man on the moon. Lithographed and engraved, the stamp was printed by the Bureau of Engraving and Printing in a quantity of 152,364,800. This was the first jumbo-size American commemorative. The engraved master die to this stamp accompanied the astronauts all the way to the Moon’s surface. An envelope bearing a proof of the stamp was also canceled in the space module. The first day cover was the most popular ever.

On September 16, 1969, the three astronauts spoke before a joint session of Congress on Capitol Hill. They presented two US flags, one to the House of Representatives and the other to the Senate, that had been carried to the surface of the Moon with them.

The Command Module Columbia is displayed at the National Air and Space Museum, Washington, D.C. It is in the central Milestones of Flight exhibition hall in front of the Jefferson Drive entrance, sharing the main hall with other pioneering flight vehicles such as the Wright Flyer, the Spirit of St. Louis, the Bell X-1, the North American X-15, Mercury spacecraft Friendship 7, and Gemini 4. Armstrong’s and Aldrin’s space suits are displayed in the museum’s Apollo to the Moon exhibit. The quarantine trailer, the flotation collar, and the righting spheres are displayed at the Smithsonian’s Steven F. Udvar-Hazy Center annex near Washington Dulles International Airport in Virginia.

In 2009, the Lunar Reconnaissance Orbiter (LRO) imaged the various Apollo landing sites on the surface of the Moon, for the first time with sufficient resolution to see the descent stages of the lunar modules, scientific instruments, and foot trails made by the astronauts.

In March 2012, a team of specialists financed by Amazon founder Jeff Bezos located the F-1 engines that launched Apollo 11 into space. The engines were found below the Atlantic Ocean’s surface through the use of advanced sonar scanning. His team brought parts of two of the five engines to the surface. In July 2013, a conservator discovered a serial number under the rust on one of the engines raised from the Atlantic, which NASA confirmed was from the Apollo 11 launch.

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