Looking Back: 55 years since the launch of Apollo 11
- Eve Carruthers
- Jul 16, 2024
- 8 min read
Written by Eve Carruthers and Luke Madgett
After US President J.F. Kennedy proclaimed on May 25th, 1961, “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,". A national goal was being rushed to be achieved in the ongoing space race against the USSR. The aim of successfully landing a man and returning him from the moon becoming of utmost importance for everyone involved in space.
The dream began to be realised on July 16th 1969 at 13:32 UTC, when Von Braun's masterpiece, the Saturn V roared off Pad 39A at Kennedy Space Center's Launch Complex. At 8.9 seconds before launch, the first stage ignition sequence started. The center engine ignited first, followed by opposing outboard pairs at 300-millisecond intervals to reduce the structural loads on the rocket. When thrust had been confirmed by the onboard computers, the rocket was "soft-released" in two stages: first, the hold-down arms released the rocket, and second, as the rocket began to accelerate upwards, it was slowed by tapered metal pins pulled through holes for half a second. (If all three stages were to explode simultaneously on the launch pad, an unlikely event, the Saturn V had a total explosive yield of 543 tons of TNT or 0.543 kilotons (2,271,912,000,000 J or 155,143 lbs of weight loss), which is 0.222 kt for the first stage, 0.263 kt for the second stage and 0.068 kt for the third stage. However, contrary to urban legend, the noise produced was not able to melt concrete.)
But, it propelled the three-man crew (Commander Neil Armstrong, Command Module Pilot Michael Collins, and Lunar Module Pilot Edwin “Buzz” Aldrin) sucessfully into the initial Earth-Orbit (of which they made 1.5 revolutions), before 2 hours and 44 minutes later reigniting the S-IVB stage for a 5-minute, 48-second burn to allow Apollo 11 to reach translunar orbit. Once placed in this orbit, the CSM (Command and Service Module), named Colombia, separated from the stage. This meant also separating from the Spacecraft Lunar-Module Adapter (including the LM, Eagle) and then docking with the LM after jettisoning and the transposition of the SLA panels on the S-IVB stage, which was injected into a heliocentric orbit 4 hours and 44 minutes into the mission.
But before we go any further into the mission, we will make a short detour to investigate the famous rocket that launched the most famous mission in all of space history; the Saturn-V.
Saturn-V: A concise guide to the world-famous rocket
The Saturn-V was the American super heavy-lift launch vehicle, an ode to the engineering capabilities of NASA at the time. From 1967 to 1973, it was extensively used by the Apollo programme (9 of 13 launches were for the Apollo programme) and to launch Skylab, the first American space station. It remains, to this day, the only vehicle to have carried humans beyond low-Earth orbit and holds the record for the largest payload capacity to low-Earth orbit (141,136kg), only rivalled by Starship, which is planned to be able to take 200,000kg of payloads into orbit. The cost for the research and development alone for the rocket was about $40.9 billion in today’s value. Designed by the German rocket engineer Wernher von Braun under the post-war ‘Project Paperclip’ agreement, the rocket had three stages: S-IC, S-II and S-IVB. In all 3 stages, LOX was used as an oxidiser for the other fuels used (RP-1, a form of kerosene, in the first stage, LH2 in the second and third stages).
The first stage carried 770,000 litres of RP-1 and 1.2 million litres of LOX (needed for combustion). At liftoff, the 5 F-1 engines on this stage produced 7.5 million pounds of thrust, then shut down at an altitude of 67 km. The first stage burned for about 2 minutes and 41 seconds, lifting the rocket to an altitude of 42 miles (68 km), and it is at this point, explosive bolts fire, and the first stage is jettisoned into the Atlantic Ocean, and a speed of 6,164 miles per hour (2,756 m/s) and burning 4,700,000 pounds (2,100,000 kg) of propellant.
Once the 5 J-2 engines, capable of 4,900 kN of thrust (tested in a vacuum), on the second stage are ignited, the interstage skirt is discarded alongside the emergency escape rocket (only usable below 19 miles altitude) Then, at 9 minutes and 9 seconds, the second stage is also jettisoned.
At this point, the third stage’s singular J-2 engine is fired up and burns for about 2.75 minutes, allowing the spacecraft to reach an orbital velocity of 17,500 mph and a maximum thrust of 225,000 pounds. Having the single engine allowed it to be gimballed (steerable) allowing the spacecraft to be manoeuvred into the right trajectory to the moon. After this burn, the vehicle had reached a sufficient speed to stay in Earth orbit and about 2.5 hours later there was a final burn at about 24,500mph (typical lunar mission escape velocity) to send the Apollo spacecraft to the moon
Planning a landing
Now, thinking about the landing of the LM 4 days later, there was a lot of planning into doing the seemingly impossible task of landing and returning men from the lunar surface. There were 3 methods to choose from to land a man down on the moon:
Earth Orbit Rendezvous (EOR): involves the use of a space rendezvous to assemble and potentially fuel a translunar vehicle in low Earth orbit
Lunar Orbit Rendezvous (LOR): in which a main craft and smaller lunar lander travel to lunar orbit. The lander independently goes to the lunar surface whilst the CSM stays in lunar orbit. After completion of the mission the lander returns and re-docks with the main spacecraft to then be discarded after crew and payload transfer.
Direct Ascent: Requires a prohibitively large launch vehicle (for the time) to allow for being able to land on the moon and fly back without a landing vehicle.
NASA agreed in favour of Lunar Orbit Rendezvous (LOR) for the Apollo program, mainly because LOR does not require a spacecraft big enough to both make the return trip from Earth orbit to splash down in the ocean, and a soft landing on the lunar surface.
Landing on the lunar regolith, and return home
Once the two crew members who were scheduled to travel to the Lunar surface had transferred into the Lunar Module (for Apollo 11 this was Neil Armstrong and Buzz Aldrin, as I’m sure you are familiar), it detached from the Command Module in lunar orbit (with Michael Collins - who actually designed the mission emblem as he wanted a symbol for "peaceful lunar landing by the United States" - in), leaving the remaining crewman to orbit the Moon alone in the command module.
The Lunar Module then began its descent towards the lunar surface, firing its small landing engine as it approached the grey terrain to avert a collision. On Apollo 11, the computer targeted landing site was deemed unsuitable by the astronauts due to the presence of large rocks (the oiginal landing spts had been chosed based on photos take on Earth. But the areas that appeared promising on photographs taken on Earth were often found to be totally unacceptable. The original requirement that the site be free of craters had to be relaxed), thus Neil Armstrong took over flight controls and skillfully navigated the module to a safer, less rocky landing site. The final site selection was based on 7 criteria:
The site needed to be smooth, with relatively few craters;
with approach paths free of large hills, tall cliffs or deep craters that might confuse the landing radar and cause it to issue incorrect readings
reachable with a minimum amount of propellant;
allowing for delays in the launch countdown;
providing the Apollo spacecraft with a free-return trajectory, one that would allow it to coast around the Moon and safely return to Earth without requiring any engine firings should a problem arise on the way to the Moon;
with good visibility during the landing approach, meaning the Sun would be between 7 and 20 degrees behind the LM
a general slope of less than two degrees in the landing area.
They landed with minimal fuel reserves, but they were safely down on the lunar surface! Neil Armstrong remarked: “The Eagle has landed.” (with Eagle being the name of the Lunar Module). They landed at 20:17:40 UTC on July 20, 1969. Armstrong proceeded to prepare to disembark the spacecraft, and climbing down the ladder became the first person to set foot on a body apart from Earth. He said the famous line of: “That’s one small step for [a] man, one giant leap for mankind.”. Humanity had succeeded in the first goal laid out in Kennedy’s speech, landing a man on the moon.
Neil and Buzz then set out on conducting several surface activities for the 2 hours and 15 minutes they were outside the module on the surface of the Moon (out of the 21 hours and 36 minutes the module was landed for). They planted the US flag, collected rock samples, and generally experienced the feeling of walking on the moon for the first time, no-one had ever done anything like this before. However, before long their time was up. They had stayed their time on the Moon, and although later missions would stay longer they would not get the opportunity to. They boarded the module, and prepared for takeoff from the surface of the Moon. The small engine on the crew compartment of the module fired, and they sped away into lunar orbit, to rendezvous with the Command Module and Michael Collins, before beginning their journey home. The calculations and timings had to be precise, there was no re-attempting this. It went perfectly, however, and soon the crew of Apollo 11 was reunited in the Command Module once again. The Lunar Module was no longer of any use, and it was jettisoned in lunar orbit, before it eventually impacted the Moon. The Command Module fired up its engine, and the crew were placed on a trajectory to take them home again.
Once they came close to the Blue Planet again, the Service Module was jettisoned, burning up in the atmosphere. Now only the capsule remained, it raced through its direct descent path into the atmosphere, never re-entering LEO. Coming in hot, the ablative heatshield did its job incredibly well, protecting the precious crew all the way through reentry. Upon reaching a low enough altitude, the three main parachutes deployed and the crew made a soft splashdown in the Pacific Ocean at 16:50:35 UTC on July 24, 1969. Kennedy’s goal had been achieved, even if he wasn’t alive to see it. The United States of America had landed men on the moon, and returned them safely to Earth. The unthinkable merely a decade prior had become history. Humanity was no longer bound by the confines of this planet, we were capable of reaching out to the stars.
The crew were picked up by the USS Hornet, with President Nixon greeting them as they were put into a Mobile Quarantine Unit. No-one had ever set foot off the Earth before, so NASA was being careful. He congratulated them on their successful mission. The United States of America had won the Space Race against the USSR. The crew were regarded as national heroes, parades were held in their honour and they toured the country. A feeling of patriotic optimism towards space was sown in the hearts of the American people.
