The Apollo 11 Journey to the Moon

Stepping on another planet was truly extraordinary; but how they got there was even more extraordinary.

As Eagle entered lunar orbit, Armstrong fired the engine to initiate a powered descent toward its surface; however, after receiving a computer alarm message he began manually controlling his descent path in order to avoid landing in a rock-filled crater.

The launch

BBC Tomorrow’s World travelled to NASA’s headquarters during the buildup to Apollo 11’s launch to witness first-hand how their astronauts were prepared for such an immense journey. These included rigorous simulations – such as lunar transits that lasted three days each!

At 9.32am on July 16, with millions watching around the globe, a massive Saturn V rocket lifted off from Cape Kennedy carrying Armstrong, Aldrin and Collins and began its historic voyage towards fulfilling President John F Kennedy’s goal of having humans walk on the Moon. It would become history.

The first stage burned for six minutes, propelling the spacecraft to an altitude of 175 kilometers and accelerating it toward orbital velocity. The second stage then burned for two and a half minutes to propel it further into lunar orbit.

On their way to the Moon, Armstrong used a navigation system to determine their landing site; but when this began guiding them towards an boulder-covered crater instead, he took manual control to prevent an imminent crash landing with only 30 seconds worth of fuel left.

At 10.39pm five hours early, Armstrong emerged from his lunar module hatch and set foot on its surface. He conducted various scientific and exploration experiments before setting foot upon it to deploy science and exploration experiments, take photographs of his surroundings, display an American flag and read an inscription plaque, photograph his surroundings as well as collect rock samples to bring back to Earth for testing purposes. A television camera mounted to his lunar module transmitted his progress live to hundreds of millions of viewers around the globe.

After some rest and recuperation time, Armstrong and Aldrin prepared for their inaugural lunar EVA (extravehicular activity). Unlike previous Apollo missions where astronauts spent multiple weeks quarantining themselves to ensure no harmful bugs had hitched a ride home from space, these astronauts simply needed to be doused with disinfectant before locking themselves inside Eagle for their EVA.

They slept fitfully until a sudden alarm started sounding due to an error in computer’s reading of spacecraft sensors – however too late to abort landing and mission controllers were unable to make decisions over re-start or not. Finally guidance officer Steve Bales called capsule communicator Charlie Duke and gave the all-clear: “We’re go on that alarm”. At that point the astronauts crawled from Columbia through an underground tunnel until Eagle was lifted onto surface via cables and released.

The orbit

By firing Eagle’s propulsion system, the two astronauts changed from their near circular orbit into an elliptical course with only 15,000 meters (50,000 feet) approaching the Moon at its closest approach point. At this low point, they fired their engine again for powered descent initiation maneuver.

This sequence reduced the altitude of the lunar module to around 15 km (8 miles) above its surface. Next, the lunar lander fired its engine again – this time to slow down in preparation for landing. As it approached the Moon from different altitudes, this procedure repeated itself five times with each attempt at landing taking about 90 minutes each time. At one stage during approach, however, navigation computer’s alarm sounded, warning it had run out of memory; however NASA simulations indicated a successful landing would still occur regardless of this warning, so Mission Control allowed them to proceed without issue.

On 20 July, Armstrong and Aldrin entered their lunar module (nicknamed Eagle), disembarked it from Earth-bound Command Module, deployed Early Apollo Scientific Experiments Package experiments, then went out onto surface collecting samples of rock and dust samples; this EVA lasted one hour 33 minutes and featured both astronauts.

Armstrong and Aldrin took numerous pictures from their lunar module of the lunar surface while using instruments familiar to sailors for centuries: telescope and sextant.

The sextant was an indispensable tool, as it enabled astronauts to determine exactly how far they had traveled since leaving Earth’s surface and was critical in managing fuel restrictions.

In order to save fuel and reduce consumable costs, Apollo 11 needed to depart its parking orbit and accelerate into an elliptical lunar orbital transfer orbit. This process, known as translunar injection (TLI), allowed it to save both time and fuel consumption. You can see its trajectory by following this link to a diagram: the red line represents the ecliptic plane while dotted green lines indicate initial, apollo, and transfer orbits respectively for its lunar module.

The descent

Time had finally come for the lander to begin its descent toward the moon’s surface, after its separation from Columbia and separation of Commander Neil Armstrong and Lunar Module Pilot Buzz Aldrin from their respective command modules Columbia. Once on its two-hour trip down towards its landing site, 26-year-old Guidance Officer Steve Bales witnessed something unusual for himself – an alarm code 1201 flashed across his monitor, warning him that its computer system had been programmed to terminate its descent if its actual rate deviated too much from planned one.

Jack Garman, the mission’s backup avionics specialist, had already informed them about this problem and gave instructions to follow its guidelines; these included firing engine at 10% maximum power in order to slow the LM down – something Bales needed in order to abort.

At this late stage in their mission, an abort would be highly risky. Furthermore, mission control had mandated that they could only abort if their actual descent rate exceeded 35 feet per second compared to what was planned; otherwise they must jettison and send back into orbit the LM.

Armstrong, an accomplished test pilot known for remaining calm under pressure, quickly recognized that their computer was sending them towards an overgrown boulder-strewn crater and took manual control of the LM. By acting in this way, Armstrong enabled them to reach a flat area with only 30 seconds remaining of fuel remaining in their tanks.

Momentous events forever changed humanity’s view of its place in the universe. Ten more American men — later joined by two dozen from other nations — would walk on the lunar surface, exploring its stark, alien terrain while returning with priceless samples of rocks and soil from this distant corner of space, helping reveal more information about our solar system.

But Armstrong and Aldrin had only just begun what would become one of the greatest feats ever accomplished by humanity.

The landing

At 9:32 a.m. EDT on July 16th, Neil Armstrong (1930-2012), Buzz Aldrin (1938-) and Michael Collins (1930-) emerged from Columbia through an interconnecting tunnel and took their places inside Eagle, their temporary lunar module for three days of exploration on the moon. As people worldwide watched in amazement as these astronauts embarked upon their historic mission.

The Lunar Module’s descent engine was activated just over two and a half minutes into its mission, providing enough force to slow it from lunar orbit, break away from Columbia, enter Lunar atmosphere and land safely on its surface. This phase ran almost precisely according to preflight plans with only minor deviations caused by an SPS (Stage-to-Orbit Stage) correction burn aimed at correcting its trajectory plan for landing on Luna.

As soon as they were on the surface, they conducted an exhaustive checklist to ensure their craft would function correctly for their return home. Due to the importance of immediately working through their checklists, they opted not to utilize the four-hour rest period scheduled roughly two hours post landing; many interpret this decision as being due to being too excited.

Armstrong and Aldrin spent nearly 2.5 hours walking across the lunar surface during which they deployed scientific experiments, photographed their surroundings, retrieved rock and soil samples for further analysis, communicated constantly with Mission Control back home, posed for pictures and displayed both an American flag as well as an inscription plaque placed there by NASA.

Aldrin communicates with Mission Control via radio about the status and condition of his lunar module’s sensors as well as the lunar surface conditions. He reads out their Landing Point Designator angle and altitude reading, explaining to Mission Control that they were being guided towards West Crater by computer guidance. Later he reported that Eagle was rolling over, rotating its legs directly towards its legs facing down onto Moon surface until Mission Control could get readings from their landing radar, which would then “lock on” with Lunar surface before starting descent downhill.