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55 Years Ago: Apollo 11 Moon landing - Part 2

MEN LAND ON THE MOON!! Words such as these were emblazoned in dozens of languages on the front page of newspapers around the world, echoing the first part of President John F. Kennedy's bold challenge to the nation, made more than eight years earlier: to land a man on the Moon. That part was successfully accomplished on July 20, 1969. A Moon expedition and the safe return to Earth of all three astronauts were now the main objectives. Commander Neil A. Armstrong, Lunar Module Pilot (LMP) Edwin E. "Buzz" Aldrin, and Command Module Pilot (CMP) Michael Collins were about to see if they could complete the historic mission.

By John Uri, NASA Johnson Space Center

At precisely 3:17:40 PM Houston time on July 20, 1969, Aldrin called out "Contact light," indicating that at least one of the three 67-inch probes hanging from the bottom of three of the LM's footpads had made contact with the Moon. Eagle drifted to the left when three seconds later, Armstrong called out, "Shutdown," followed by Aldrin's, "Okay. Engine stop," indicating the DPS engine was shut off.

They were on the Moon.

In Houston, Duke noted via telemetry that the engine had shut down, and called to Armstrong and Aldrin, "We copy you down, Eagle."

Armstrong responded with the historic words, "Houston, Tranquility Base here. The Eagle has landed."

It should be noted that for everyone on Earth, the first Moon landing was purely an audio experience. Controllers in MCC had the added benefit of telemetry from the spacecraft, but there was no live television of the landing. A 16-mm silent film camera mounted in the right-hand (Aldrin's) window recorded the event, but was not available for viewing until it was returned to Earth and developed. An annotated video of the landing was prepared from this film (courtesy of Apollo Flight Journal), and synchronized with space-to-ground communications, several loops in Mission Control, and video clips from MCC.

After a few minutes, Aldrin provided the first verbal description of their surroundings, including the types and sizes of rocks and the general color of the surface. Duke radioed to them, "Be advised there are lots of smiling faces in this room and all over the world," prompting Armstrong's response, "Well, there are two of them up here."

Armstrong reported that neither he nor Aldrin had any trouble adjusting to the one-sixth gravity on the lunar surface. He continued with a more detailed description of their view out the forward windows.

As they continued their post-landing activities, Armstrong called MCC to advise that he and Aldrin would like to forego the planned rest period before their Extra-Vehicular Activity (EVA), or spacewalk, and MCC concurred with their proposal. Aldrin made the following request to anyone who might be listening, "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 proceeded to take communion with a chalice and consecrated wine he brought along for the occasion.

VIDEO: NASA Administrator Bill Nelson on the 55th Anniversary of Apollo 11. [Credit: NASA]

He and Armstrong then began preparations for their historic spacewalk, including donning their Portable Life Support Systems (PLSS), the backpacks that provided oxygen, removed carbon dioxide, and enabled communications. The Green Team of flight controllers led by Clifford E. Charlesworth, with Bruce McCandless serving as Capcom, took their positions in Mission Control to help Armstrong and Aldrin prepare for and execute their EVA. They reconfigured Eagle's cabin for depressurization, donned their helmets, visors, and gloves, and then opened the valve that vented the cabin.

Aldrin opened Eagle's forward hatch, which swung inward toward him, giving Armstrong access to the outside front porch. Aldrin added, "About ready to go down and get some Moon rock?" He helped Armstrong navigate through the narrow confines of Eagle's hatch and onto the front porch. Once on the ladder, Armstrong pulled a lanyard that released the Modularized Equipment Stowage Assembly (MESA) on the side of Eagle's Descent Stage, on which was mounted a black and white TV camera, allowing hundreds of millions of viewers on Earth to see him descend the ladder down to the landing leg's footpad.

As a precaution, he practiced the three-foot jump back up to the ladder's first rung, made easier in the one-sixth lunar gravity. Once back down on the footpad, Armstrong described that the footpads had only sunk one or two inches into the lunar dust, which he noted was fine-grained, almost powdery.

Armstrong announced, "I'm going to step off the LM now." And at 9:56 PM Houston time he did just that, firmly planting his left foot onto the lunar surface, proclaiming, "That's one small step for a man, one giant leap for mankind."

VIDEO: Moon landing. [Credits: National Archives]

VIDEO: Footage from the Apollo 11 moonwalk that was partially restored in 2009. [Credits: NASA]

After taking his first tentative steps on the lunar surface, Armstrong began his first tasks of the spacewalk, including receiving the Hasselblad still camera from Aldrin via a lanyard and pulley system, using it to take the first photographs of Eagle to document how it fared during the landing as well as of their surroundings, and collecting the contingency sample of lunar material in case they had to make an emergency departure. A few minutes later, Aldrin began his descent to the surface, commenting on the way out of the cabin, "Now I want to ... partially close the hatch. Making sure not to lock it on my way out." This prompted a laugh from Armstrong who commented, "A particularly good thought."

Once Aldrin was on the surface, he and Armstrong unveiled the commemorative plaque that was mounted on the landing leg and read the words that were inscribed on it, "Here men from the planet Earth first set foot upon the Moon, July 1969 A.D. We came in peace for all mankind." The plaque bore the signatures of the Apollo 11 astronauts as well as of President Richard M. Nixon.

Armstrong then removed the TV camera from the MESA, carried it about 60 feet from the LM, and mounted it on a tripod so the world audience could watch their subsequent activities. Closer to the LM, Aldrin was setting up the Solar Wind Collector (SWC) experiment, a sheet of aluminum that was exposed to the Sun for 77 minutes to collect ions in the solar wind. Near the end of the EVA, Aldrin rolled up the foil and stowed it for return to Earth for analysis by scientists.

Their next task was to remove the Lunar Flag Assembly attached to Eagle's ladder and set up the American flag about 20 feet from the LM. Because in the vacuum on the Moon there is no way for the flag to stay unfurled, a telescoping horizontal metal rod was inserted along the top of the 3-by-5-foot nylon flag. During the deployment, this metal rod did not extend all the way and left the edge of the flag somewhat wrinkled, giving it the appearance of waving in a non-existent lunar breeze.

Aldrin began to experiment with different types of locomotion in the one-sixth gravity when Capcom McCandless requested that both astronauts position themselves in front of the TV camera. For the next two minutes, Armstrong and Aldrin talked to President Nixon in the White House's Oval Office, who offered the nation's congratulations on their historic accomplishment.

The phone call concluded and Armstrong and Aldrin resumed their tasks, which included Aldrin performing soil cohesion tests by kicking the lunar surface with his boot and observing the resulting sprays of dust, which in the vacuum and one-sixth gravity on the Moon behaved differently from how they would on Earth. Armstrong returned to the MESA to retrieve the equipment for the bulk sample collection of lunar material. Aldrin picked up the Hasselblad to take photographs for the Bootprint Penetration Experiment, and took panoramic photos of the landing site, incidentally taking one of the few photographs of Armstrong on the surface as he packs the bulk sample at the MESA.

After more photography, Aldrin handed the camera back to Armstrong and walked to the back of the LM where the Scientific Equipment (SEQ) bay containing the Early Apollo Surface Experiment Package (EASEP) was located. The EASEP consisted of two experiments, the Passive Seismic Experiment Package (PSEP) to measure Moon quakes and the Laser Ranging Retro-Reflector (LRRR) that contained an array of mirrors to reflect a laser beam sent from Earth for precise measurements of the Earth-Moon distance. Aldrin removed the two experiments from the SEQ bay and carried them about 40 feet from the LM where he deployed the PSEP and Armstrong the LRRR.

At this point, they were running about 30 minutes behind the timeline, but their consumables were within limits so McCandless called to tell them that Mission Control had given them a 15-minute extension on the EVA. He also mentioned that scientists had activated the seismometer and it was picking up the vibrations from their footsteps.

Aldrin returned to the MESA to begin getting two core samples as part of the documented samples. Armstrong jogged 180 feet to Little West Crater that they had overflown during the descent and took a series of panoramic shots before jogging back to the LM to assist Aldrin with the core samples. Finishing the core samples, Aldrin rolled up the solar wind experiment. Armstrong collected about 20 rock samples weighing about 13 pounds.

And with that, it was time to finish the EVA. Armstrong and Aldrin gathered the film magazines and closed up the rock boxes. Armstrong scooped up about 13 pounds of lunar dirt as packing material for the rocks in the boxes as Aldrin climbed up the ladder and back into the LM. From there he helped Armstrong transfer the rock boxes up to the cabin using the lanyard system. A film cassette attached to the first rock box fell off and into the lunar dirt, but Armstrong retrieved and reattached it. The dirt attached to the cassette would later cause an accidental exposure to one of the employees once in the Lunar Receiving Laboratory in Houston. They hauled the second rock box up to the cabin without incident.

Just before Armstrong headed up the ladder, he reminded Aldrin about a small package of commemorative items that they wanted to leave on the surface. Aldrin tossed it down through the hatch from inside the cabin. The items included a silicon disc etched with goodwill greetings from 73 world leaders, an Apollo 1 patch commemorating astronauts Virgil I. Grissom, Edward H. White, and Roger B. Chaffee lost in the 1967 fire, two Soviet medals honoring cosmonauts Vladimir M. Komarov killed in the Soyuz 1 accident and Yuri A. Gagarin, the first man in space killed in an airplane crash in 1968, and a small gold olive branch, identical to ones the astronauts carried to the Moon and back for their wives.

Armstrong then jumped up to the third rung of the ladder and climbed the rest of the way into the cabin. Within a minute they had the hatch closed and began repressurizing the LM. They removed their PLSS backpacks, took photographs out the windows to use up their remaining film, and ate a well-earned meal. Aldrin realized that probably while he was removing his PLSS, he broke the circuit breaker that armed the ascent stage engine, critical for their departure the next day. Fortunately, they were able to use a felt-tip pen to depress the breaker button.

Director of Flight Crew Operations Donald K. "Deke" Slayton called to the crew, "That's a real great day, guys. I really enjoyed it."

Armstrong replied, "Thank you. You couldn't have enjoyed it as much as we did," and Aldrin said, "It was great."

They then depressurized the LM cabin and threw their PLSS backpacks out the hatch along with a jettison bag containing their lunar boots and other items no longer necessary. This freed up space in the cramped cabin and reduced the weight of the LM at liftoff.

Since the TV camera on the surface was still transmitting, MCC was able to observe the jettisons, and the PSEP recorded the items hitting the surface, prompting Armstrong to comment, "You can't get away with anything anymore, can you?" They then repressurized the cabin for the final time.

Their last duty before they turned in for a well-deserved, albeit restless, night's sleep, having been awake for 21 hours, was to turn off the TV camera. Aldrin curled up on the floor of the LM while Armstrong devised a hammock and slept on the ascent stage engine cover. All was quiet on the Moon, but while the astronauts slept the American flag they planted shifted position as it settled in the loose lunar soil.

The journey home
"Tranquility Base, Tranquility Base, Houston," called Capcom Ronald E. Evans on July 21, 1969, to awaken Apollo 11 astronauts Neil A. Armstrong and Edwin E. "Buzz" Aldrin after their night's sleep on the Moon. Armstrong responded with a crisp, "Good morning Houston. Tranquility Base," and Aldrin went on to describe how he had slept on the floor of the Lunar Module (LM) Eagle while Armstrong slept on the ascent engine cover with a make-shift sling to hold his legs up. Both slept with their suits, helmets, and gloves on since the temperature in the cabin was a chilly 61 degrees F. Neither man had slept too soundly, partly from the excitement of the previous day's activities, and partly from the unusual sleeping arrangements. Moreover, the Earth was shining through a navigation telescope right into Armstrong's eyes.

Evans had earlier awakened Michael Collins orbiting aboard the more spacious Command Module (CM) Columbia, who had a more restful night. All three men prepared for Eagle's liftoff from the lunar surface and rendezvous and docking with Columbia. Before departure, Armstrong and Aldrin used the 16-mm film camera to once more document their landing site through the LM's windows, showing that overnight the American flag had shifted position, apparently settling in the loose lunar soil.

As an historical side note, as Armstrong and Aldrin were preparing for their departure from the Moon, the Soviet Luna 15 robotic spacecraft, launched three days before Apollo 11, fired its retrorocket after completing 52 lunar orbits. Signals with the craft were lost four minutes later and it is believed to have crashed in the Mare Crisium approximately 500 miles from Tranquility Base, traveling at an estimated 300 miles per hour.

After ensuring that all switches and circuit breakers were properly configured, including the one that arms the ascent stage engine that was accidentally broken by Aldrin's Portable Life Support System backpack and that had to be activated using a felt-tip pen, Evans called up, "You're cleared for takeoff." Aldrin responded, "Understand. We're number one on the runway."

After a 21-hour stay, the LM's Ascent Propulsion System (APS) engine fired precisely on time, lifting Eagle's ascent stage off the surface of the Moon, using the descent stage as a launch pad. Aldrin reported, "We're off. Look at that stuff [insulation from the decent stage] go all over the place. Look at that shadow. Beautiful." Armstrong, for the second time during the mission, radioed, "The Eagle has wings." Aldrin had installed the 16-mm film camera in his window but didn't activate it until six seconds after liftoff. They reported that the ascent stage was giving them a very smooth and quiet ride. The seven-minute APS burn placed them in a 54-by-11-mile orbit. Armstrong proclaimed, "The Eagle is back in orbit, having left Tranquility Base."

An hour later, with both Eagle and Columbia behind the Moon, the LM's Reaction Control System (RCS) thrusters fired for two minutes to circularize the LM's orbit to be 58 by 53 miles. Another hour later, a one-minute RCS burn changed Eagle's orbit so it was a constant 17 miles below Columbia's. At this point, the two spacecraft were 100 miles apart with Eagle in the lower orbit catching up to Columbia. A final burn 30 minutes later put Eagle on an intercept course with Columbia. Armstrong then made a short braking burn followed by several smaller midcourse maneuvers to complete the rendezvous.

The astronauts in the two vehicles could now see each others' spacecraft, and Collins filmed Eagle's final approach. As the two spacecraft neared each other, they came around from the Moon's far side and Collins was treated to a view of Eagle back-dropped by the Earth rising over the lunar horizon. Less than four hours after lifting off from the lunar surface, and with Armstrong holding Eagle in position, Collins guided Columbia in for the docking. The two craft were reunited after spending nearly 28 hours apart.

With the hatches open between the two spacecraft, Armstrong and Aldrin began to clean up as much of the lunar dust as they could, part of the back-contamination prevention procedures, and transferred the lunar rock boxes, film cassettes, the solar wind experiment, and other items from Eagle into Columbia. Within two hours they completed all the transfers, closed the hatches for the final time and jettisoned Eagle, which remained in lunar orbit until crashing on the Moon's surface several months later.

Apollo 11 orbited the Moon for another five hours, then while behind the Moon fired the Service Propulsion System (SPS) engine for the two-and-one-half-minute Trans Earth Injection (TEI) burn at the end of Columbia's 30th lunar orbit to send the astronauts homeward. At the time of the burn, Columbia was 20 miles in front of and 1 mile below Eagle. As they rounded from behind the Moon, Armstrong called down to Capcom Charles M. Duke in Mission Control, "Time to open up the LRL doors, Charlie." He was referring to the Lunar Receiving Laboratory at the Manned Spacecraft Center, now the Johnson Space Center in Houston, where the astronauts were quarantined after their mission and the Moon rocks were first examined. Duke responded, "We got you coming home. It's well stocked." After TEI, the astronauts took their last photographs of the lunar far side and of an Earthrise.

The astronauts took a series of photographs of the receding Moon and placed their spacecraft into the Passive Thermal Control (PTC) or barbecue mode, rotating along the spacecraft's longitudinal axis three times each hour to evenly distribute temperature extremes.

Director of Flight Crew Operations Donald K. "Deke" Slayton radioed up to the crew, "This is the original CapCom. Congratulations on an outstanding job. You guys have really put on a great show up there. I think it's about time you powered down and got a little rest, however. You've had a mighty long day here. Hope you're all going to get a good sleep on the way back. I look forward to seeing you when you get back here. Don't fraternize with any of those bugs en route, except for the Hornet."

Slayton was making a humorous reference to any possible Moon germs the astronauts may be carrying back with them which necessitated the post-flight quarantine to prevent back contamination, which began as soon as they arrived aboard the prime recovery ship the USS Hornet (CVS-12) after splashdown in the Pacific Ocean. As the Apollo 11 astronauts prepared for their first sleep period of the Earthbound journey, Mission Control finally lost contact with Eagle, still in lunar orbit, as its batteries could no longer power its navigation system to point its antenna toward Earth.

Shortly after the astronauts awoke from a 10-hour rest period, they passed out of the Moon's sphere of influence and into the Earth's, and began accelerating toward their home planet. At a distance of 194,500 miles from Earth, they conducted an 11-second midcourse maneuver using the Service Module's RCS thrusters to refine their trajectory for entry into Earth's atmosphere.

The astronauts treated Earth-bound viewers with a 15-minute television broadcast, beginning with a view of the receding Moon. They turned the camera into the cabin, and Armstrong displayed the two boxes that contained the precious samples of lunar rocks and soil. They demonstrated food preparation in their spacecraft and advancements that had been made in the types of food available to them. In brief physics lessons, Aldrin demonstrated how gyroscopes work and Collins displayed the behavior of fluids in zero-gravity. They ended the broadcast by showing viewers the Earth. The rest of their day was spent leisurely before they settled in for another 10-hour rest period, about 163,000 miles from home.

When they awoke for their final full day in space, they had closed the distance to Earth to 131,000 miles as they continued to accelerate. Capcom Owen K. Garriott informed them that Mission Control decided that since their trajectory was so precise, a planned midcourse maneuver that day was not necessary. They soon passed the halfway point between Earth and Moon, 118,424 miles from each.

During a 12-minute TV broadcast, the astronauts provided their reflections on the mission. Collins stressed the complexity of the flight and the hard work done by the thousands of workers to make Apollo 11 possible. Aldrin opined that the flight represented not just the work that went into it but also humanity's innate curiosity to explore. Armstrong concluded by recognizing everyone who was responsible for making Apollo 11 possible and expressed special thanks to the workers who built their spacecraft. As a closing scene, the astronauts zoomed in on the Earth, now 105,000 miles away. Armstrong's wife Jan and their two children, Collins' wife Pat and their children, and Aldrin's son Andy visited the Mission Control Viewing Room during the broadcast.

Shortly before they retired for their last night in space, Capcom Duke informed the astronauts that due to a weather system approaching their nominal end-of-mission splashdown point, a new area 250 miles to the northeast would be targeted. No midcourse maneuvers were necessary, the CM used its lift capability to extend the entry trajectory. Hornet was already speeding toward the new location. President of the United States Richard M. Nixon departed on his journey to meet the Apollo 11 astronauts aboard Hornet.

Last week Apollo 11 launch and Moon landing - Part 1.

Learn more about NASA history at nasa.gov/history/.

A big thanks to NASA and author John Uri for penning such interesting and detailed accounts for all of us to enjoy.

Published July 2024

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