On July 24, 1969, Armstrong and Aldrin successfully descended to the Moon, taking photographs, collecting specimens from rocks and soil samples, installing a laser-ranging reflector and passive seismograph (a moonquake detector), as well as speaking with President Nixon.
But their descent was far from uneventful – during a powered descent an alarm went off that neither Armstrong nor Aldrin understood.
The launch
The Saturn V rocket successfully delivered three modules into Earth orbit: the command module (CM), with its classic space capsule shape and housing astronaut quarters and flight controls; an expendable service module providing propulsion and support systems; and lunar module (LM). After separation from CM, Aldrin and Armstrong took part in lunar landing by ascending from their respective modules through a tunnel connecting both modules onto lunar surface.
On the morning of 20 July, Armstrong and Aldrin took off in their lunar lander (LM), leaving behind both crewmembers. For two and a half hours they deployed science experiments, photographed their surroundings, displayed an American flag, read an inscription plaque on the lunar surface, spoke with President Nixon via radio, collected rock samples for return home as well as soil samples; cameras mounted within and outside their LM provided documentation of their journey back.
At this late stage in the landing sequence, Armstrong saw that his lunar module computer indicated they were headed toward West Crater and its boulder-strewn terrain would make landing challenging. Since an abort could prove dangerous at such an advanced stage in landing procedure, he slowed his descent manually while manually maneuvering to avoid it before landing with minimal fuel remaining remaining onboard.
Armstrong and Aldrin had completed their inspection of their lunar module’s systems, and were ready to start their return flight home. But their lunar module’s lander radar wasn’t functioning correctly; it transmitted too long a signal for ground control receivers to receive. Armstrong estimated this error was three seconds long, and radioed Mission Control: “Houston, Tranquility Base here: We’re landing.”
Armstrong and Aldrin returned to the LM, then descended back down to the Moon surface for another night before ascending aboard Eagle in order to rendezvous with Collins in the CSM and dock with her again. Soon thereafter, their radar lander radar was restored, and Armstrong and Aldrin climbed back onto it before setting foot back onto its surface for their return journey homeward.
The flight
Apollo 11 proved surprisingly unremarkable for a mission billed as “moonshot,” with astronauts emerging from their battered CM capsule after three days to find themselves exhausted but relieved at having accomplished one of President Kennedy’s national goals.
Armstrong and Aldrin spent about two hours exploring the lunar surface outside their LM, taking photos and setting up scientific experiments that would remain on it, such as seismographs for measuring moonquakes and laser-ranging retroreflectors to measure distance from Earth to Moon. They also collected samples of lunar soil and rocks.
Throughout their EVA, Armstrong and the other astronauts maintained constant radio communications with Mission Control in Houston and were regularly asked by geologists watching from Houston about aspects of their exploration. At one point Armstrong disappeared from TV camera view, which alarmed geologists; but soon enough he was located just meters away, having become fascinated with some interesting rock formations.
After returning to the LM, the astronauts made more photographs and conducted some housekeeping duties–such as performing voice tests, telemetry checks and oxygen-purge system testing. At approximately 1:30 p.m. they fired their propulsion system to modify their lunar orbit from circular to an elliptical one that would bring them close to its lowest point–known as the Sea of Tranquility.
After the Eagle returned to lunar orbit, its astronauts performed a series of power-down maneuvers in preparation for landing. On 21 July at 2:56 GMT, Armstrong first exited his LM and nineteen minutes later Aldrin followed suit.
As the astronauts had practiced their landing sequence numerous times before, everything went off smoothly–except for a momentary glitch when an alarm signaled that lunar surface radar readings did not match those from Primary Guidance and Navigation System (PGNS). Aldrin quickly resolved this issue by firing up his descent engine in order to power down toward lunar surface.
The landing
After 21 hours and 38 minutes on the moon, Armstrong and Aldrin returned to their battered command service module (CM), located between LM and Columbia orbiting spacecraft, to undergo a lengthy checklist to make sure their return trip would go as smoothly as planned. Instead of resting for 4 hours as scheduled, Armstrong and Aldrin went out exploring instead, taking photos, collecting rock samples, displaying an American flag, reading an inscription plaque, conducting science experiments and even setting up passive seismographs to measure moonquakes and meteor impacts long after their return home!
The Lunar Module, or LM, appeared like an intricate geometry project with spindly legs but actually consisted of two sections: an ascent stage with gold-and-black paintwork at its lower section; and a white-and-silver upper section which housed pressurized chambers, hatches for exiting, science equipment, pressurized compartments for crew members, pressurized compartment for pressurization purposes, pressurization control chamber and most of their scientific and exploration equipment. Once on the lunar surface they jettisoned its ascent stage; leaving its useless orbit around our planet’s moon’s surface untouched.
Once the Lunar Module began its descent toward the Moon, astronauts fired their engine for about 10 seconds to shift into free fall toward its gravity and establish an elliptical orbit that put them closer to freefalling towards it. They then initiated powered descent initiation maneuvers to reduce rate of descent and provide greater control over landing location.
Mission Control continued tracking the Lunar Module as it neared the Moon. Aldrin reported warning lights in his cockpit triggered when the lander lost contact with its landing radar system, as well as regularly providing altitude and speed updates of their descent. By the time Aldrin made contact with Mission Control at 700 feet down, approximately five percent of their fuel had already been depleted; Aldrin needed permission from them before landing could proceed and Mission Control granted this request; at least for now.
Once back on board the CM, the astronauts donned biological contamination suits in case any harmful moon bacteria had made its way back onto them. A mobile quarantine ship – an Airstream trailer modified to resemble a spaceship – was transported them for 21 days of observation and tests at NASA hospitals located throughout Houston.
The return
Armstrong and Aldrin quickly deployed scientific equipment upon landing, such as television cameras to transmit back their images back to Earth; solar wind composition experiment; seismograph for measuring moonquakes and Laser Ranging Retroreflector; in addition to taking numerous photographs of themselves, their surroundings, LM spacecraft and each other using both still and motion picture cameras.
As they made their return journey back to Earth, Armstrong noticed strange warning alarms coming from within the LM and realized its auto-landing program was trying to place them directly in West Crater crater; taking semi-manual control over its descent engine to steer away from it.
At 2:16 p.m. in Site 2 of the Sea of Tranquillity, with only 30 seconds remaining in their fuel reserve, Armstrong announced: “That’s one small step for man and one giant leap for humanity!” via broadcast television speech around the globe to 600 million viewers watching at home.
At landing, the astronauts clad themselves in protective suits against moon bacteria which might pose health threats on Earth and were observed and treated within their damaged CM capsule for 21 days before they could return home.
The crew of LC-36 were kept busy during their two and a half-hour mission on the lunar surface, working hard to achieve their primary mission objectives of deploying science and exploration equipment, photographing their surroundings, displaying an American flag, reading a plaque signed by President Richard Nixon, collecting rock samples for geologists, communicating with ground control, collecting rock and soil samples for geologists and communicating with ground control using their ladder onboard the Lunar Module (LM).
Armstrong made a famous proclamation when they returned to the Eagle, declaring, “That is one small step for man, but one giant leap for humanity.” While studies have disputed this particular quotation from Armstrong himself, its significance cannot be denied.