Looking back at the Apollo moon landings

The success of Artemis I means we’re looking at the exciting prospect of returning humans to the moon. If all goes to plan, humans may step onto the moon’s surface again as early as 2025, during the planned Artemis III mission.

The Artemis moon missions are building on what we learnt from the Apollo moon missions in the 1960s and 1970s, and the naming of the Artemis programme reflects that. Artemis was the Greek goddess of the moon, making the name particularly apt, but she was also the twin sister of the sun god Apollo.

With the moon once more within reach, it feels like an appropriate time to reflect on the last time humans really connected with it. This article is the first of a series looking at humanity’s first steps on the moon.

In this introductory post, we’ll talk about how many people have been to the moon and how they survived on its surface.

How many people have walked on the moon?

There have been six crewed moon landings in total, all of which were part of NASA’s Apollo programme: Apollo 11, Apollo 12, Apollo 14, Apollo 15, Apollo 16 and Apollo 17.

To date, only 12 people have stepped onto the surface of the moon: two astronauts from each of the listed Apollo moon landings. All of them were white American men, and all of them performed their moonwalks between July 1969 and December 1972: the span of just three and a half years, over half a century ago.

Including the 12 who have walked on it, 24 people in total have travelled to the moon. Again, all of these journeys took place during the Apollo programme. Each of the six moon landings included a third crew member who orbited the moon without landing, and the crewed missions Apollo 8, Apollo 10 and Apollo 13 also visited the moon, although they didn’t land.

Three astronauts – Jim Lovell, John Young and Gene Cernan – have travelled to the moon twice, which is why these nine missions with three-person crews add up to 24 people, rather than 27.

Artemis II, scheduled to launch and travel around the moon next year, is expected to add four more people to the number of moon visitors: Victor Glover, Jeremy Hansen, Christina Koch and Reid Wiseman.

How did Apollo astronauts survive on the moon?

There were a lot of challenges to overcome in order for the astronauts to be able to survive and explore comfortably on the moon. For example, their spacesuits needed to be pressurised, as humans cannot survive in a vacuum.

Here are a few of the other challenges that the Apollo astronauts’ spacesuits needed to address:

• Perhaps most obviously, humans need to breathe oxygen, which is not readily available on the moon. You may have noticed that, in photographs and videos of the moon landings, each astronaut seems to have a large backpack attached to the back of their spacesuit. This backpack is a portable life support system supplying them with oxygen from a tank. If necessary, the tank could be topped up from the lunar lander’s oxygen reserves.
• Humans also breathe out carbon dioxide, which will build up to dangerous levels in the confined environment of a spacesuit if it’s not removed. The portable life support system filtered the air supply inside the suit through a lithium hydroxide cartridge. The lithium hydroxide reacted with carbon dioxide to create lithium carbonate and water, removing the carbon dioxide from the air supply inside the suit.
• Without the protection of Earth’s atmosphere, objects on the moon can experience extreme temperatures, ranging from over 100°C in direct sunlight to below -100°C at night. To protect against these temperatures, the astronauts’ spacesuits needed to be extremely well insulated.
• However, the spacesuit also needed to prevent the astronaut from overheating. Without any means of cooling down, the astronaut’s body heat and the heat generated by the life support system would build up to potentially dangerous levels inside the spacesuit. Beneath their outer spacesuits, Apollo astronauts wore full-body garments made up of flexible fabric-covered tubes; you can see an example here on the National Air and Space Museum’s website. Water was cooled in the portable life support system and pumped through these tubes to keep the astronauts cool.
• In addition to using water for cooling purposes, the spacesuit had a water bag for the astronauts to drink from during excursions. The bag had a valve to ensure that water only came out when it was actively being drunk, preventing liquid from leaking into the spacesuit.

In later posts, we’ll talk about the individual manned Apollo moon landings, from Apollo 11 to Apollo 17. We’ll also take a moment to look back at Apollo 13, which didn’t manage to land on the moon but was still a significant mission in many ways, and we’ll reflect on how Apollo 7 to Apollo 10 laid the foundations for the landings to take place. The Apollo missions were a fascinating achievement, so we’re looking forward to delving deeper into them, and we hope you enjoy coming along for the ride.

The next post in our Apollo series will take a closer look at the Apollo spacecraft and the roles of the crew members aboard. We hope to see you there!

Cover image: NASA

Darwin Innovation Group is a UK-based company that provides services related to autonomous vehicles and communications. If you’re interested in working with us, take a look at our careers page. If you’d like to know how we can help your organisation make use of autonomous vehicles, contact us. You can also follow us on LinkedIn or Twitter.