Today marks 45 years since Neil Armstrong and Buzz Aldrin left the lunar surface. Apollo 11’s lunar module Eagle lifted off from the Sea of Tranquility at 5:54pm GMT on 21 July 1969. This first lunar landing mission certainly stands out among the ten manned Apollo flights, so much so that it’s easy to ignore the missions that came before and after Apollo 11. But it was the missions that preceded it that made the first lunar landing possible. And true to its triumph as an engineering flight, Apollo 11 really was the sum of its parts.
In January of 1967, a fire ripped through the Apollo 1 spacecraft during a prelaunch test, claiming the lives of all three astronauts on board. The fire not only raised concerns about the spacecraft, it threw a major wrench in NASA’s plan to land men on the Moon within the decade. By September, major changes were already being incorporated into the spacecraft, and management was looking ahead at a mission plan that would get the agency back on track.
NASA’s Manned Spacecraft Centre proposed to the Office of Manned Space Flight a sequence of missions building on one another leading up to a lunar mission. Each flight would accomplish one of more goals associated with the lunar landing, and when all the goals were met the next mission in line would be cleared for a lunar landing.
The missions were labeled alphabetically, A through J. The A and B missions were unmanned flights to demonstrate that the spacecraft were up to the challenge of a lunar mission. The A mission was a test of the command and service module, a goal achieved on Apollo 4 and Apollo 6, and the B mission was a test of the lunar module, achieved on Apollo 5.
Missions C through E were manned missions in Earth orbit, flights that would allow the astronauts to familiarize themselves with their spacecraft close to home. They would have a faster route home if anything went wrong. The C mission was a “shakedown cruise” of the command-service module in Earth orbit; the D mission added the lunar module, and the E mission took both spacecraft into a higher orbit to simulate returning directly from the Moon. These didn’t go exactly as planned. A delay in the lunar module’s development forced some changes. Apollo 7 flew the C mission, then Apollo 8 flew what’s become known as the C-prime mission: the crew took the command-service module alone to the Moon. Apollo 9 flew a D mission with the two spacecraft, the command-service and lunar modules, in Earth orbit.
The F mission was the last mission before the lunar landing attempt. This dress rehearsal was flown by Apollo 10. The crew went through a complete lunar landing mission but stopped just short of the Moon. The G mission would be the first lunar landing.
The progression was such that if any mission failed or any major objectives weren’t met, NASA could add more missions into the sequence. If something went wrong with dress rehearsal flight, NASA had the option of flying another F mission before going for the G mission. So it was really by luck, and very good planning, that NASA was ready for a landing mission when Apollo 11 launched. Every mission that preceded it worked out all the details of the lunar landing flight. All that was left for Neil Armstrong and Buzz Aldrin to do was land on the Moon.
Subsequent missions added more science goals to the Apollo Moon landings. The H missions were precision landings missions with two-day stays on the surface. The I missions were longer duration missions still that incorporated more sophisticated science instruments into the surface payload. The J missions were even longer missions that included three moonwalks and extensive surface operations thanks to the Lunar Roving Vehicle. Apollos 12 and 14 flew H missions, the I missions were cancelled, and the final three flights, Apollos 15, 16, and 17, flew J missions.
Without Apollos 7, 8, 9, and 10 completing their primary goals, Apollo 11 wouldn’t have been the successful first lunar landing missions it was. And by the same token Apollo 11 opened the door for NASA to proceed with the advanced surface missions that followed.