The Apollo program was a series of American spaceflights prepared from 1961 and carried out between 1966 and 1972. The goal of the program was to land a human on the Moon and then bring him safely back to Earth. The task was accomplished in 1969 during the Apollo 11 mission. The program continued until 1972 in order to conduct more detailed scientific exploration of the Moon: the Americans landed on the Moon six times. The total cost of the program amounted to 25.4 billion dollars. The amount of material collected and brought back to Earth was 381.7 kg (more than two thousand samples). Landing a human on the Moon required only six test flights. The name of the program came from Apollo, the son of Zeus and Leto.
A name had already been chosen for this not yet fully defined project. Abe Silverstein, head of the Office of Space Flight Programs, who had come up with the name Mercury a year earlier, proposed the name Apollo. As with most American space programs, the name was taken from ancient mythology. In Greek mythology, Apollo, the patron of music, medicine, and knowledge, was often identified with Helios, whose horse-drawn chariot carried the Sun across the sky.
The program was developed in 1961 at NASA’s request. It assumed that the first human landing on the Moon should take place between 1968 and 1970. Before its implementation, extensive studies of the Moon’s surface and its surroundings were carried out using lunar probes: Ranger, Surveyor, and the Moon-orbiting satellites Lunar Orbiter.
The Apollo program was the third American human spaceflight program, after Mercury and Gemini. Apollo was commissioned by President Eisenhower’s administration to expand the crewed spaceflights begun under the Mercury program. It was then transformed by President Kennedy into a program for flights to and landings on the Moon. The main Apollo spacecraft consisted of a cone‑shaped command module attached to a cylindrical service module. During the flight, the astronauts stayed in the command module.
The service module was equipped with an engine that was used to place the spacecraft into lunar orbit and later enabled it to leave that orbit and head back toward Earth. It was also used for occasional course corrections. The service module contained fuel for the main engine, as well as fuel, oxygen, and life-support systems. The astronauts entered the command module through a side hatch, which was airtight and fitted with one of the five windows located in the command module.
Through an access tunnel the astronauts moved to the lunar module. In the conical section of the command module there were three parachutes used to slow the capsule during splashdown. Contact with Earth was maintained via a parabolic antenna consisting of four dishes. The spacecraft’s computers had less computing power than today’s mobile phones. The control instruments were similarly simple. Yet, using primitive computers, 24 cameras, 566 switches, and a small telescope for tracking stars, the astronauts were able to fly to the Moon, land there, and return to Earth.
The command module was the only element that returned to Earth after a successful or partially successful mission. A total of 4,000 technicians were involved in the design and construction of the spacecraft. It took 52 months from the first plans to the construction of the first spacecraft.
The journey to the Moon required a new kind of rocket designed solely for that purpose. The three‑stage Saturn V rocket made it possible for United States astronauts to travel to the Moon. NASA built 15 rockets. Two of them never launched and are now museum exhibits. After President Kennedy’s declaration, sending an American to the Moon became a national priority, and the country began to support the Apollo program. Initially, there were plans to use the Nova rocket for this purpose. A rocket equipped with eight F‑1 engines was chosen, which could send the spacecraft on a direct flight to the Moon ending with a landing on its surface. However, the Nova project was ultimately abandoned. It was replaced by the concept known as Lunar Orbit Rendezvous (LOR) – the meeting of two spacecraft in lunar orbit. LOR made it possible to use a smaller launch vehicle. The decision was made, and work on this solution began in earnest.
By this point, nothing even roughly resembling the Apollo spacecraft had reached space. The situation changed on 28 May 1964 with the Saturn‑Apollo 6 (SA‑6) flight. This was not a crewed mission, and the spacecraft itself was just another mock‑up (BP‑13). Apollo was finally in space – or at least something more or less similar to Apollo.
Up to this time, the Little Joe II and Saturn I flights tested abort systems, mock‑ups of the command module, and the Saturn‑Apollo combination, culminating in the recognition that Saturn‑Apollo was ready for operational use three years earlier than planned. These tests also revealed problems, such as defects in the protective cover of the command module, which were gradually resolved.
Further tests with Saturn I and Little Joe II verified the launch escape system (LES) in various emergency conditions, including flight breakup and maximum dynamic pressure (Max Q), and placed Pegasus satellites into orbit using Apollo service‑module mock‑ups as carriers. The SA‑9, SA‑8, and SA‑10 flights were the last to use Saturn I rockets.
On 20 January 1966, the A‑004 test with Little Joe II completed the series of LES/abort tests, while preparations were underway for the Saturn IB rocket and work on Saturn V was still not finished. On 26 February 1966, the first Saturn IB launched the first real Apollo spacecraft on a suborbital trajectory. To distinguish it from earlier trials, the SA‑201 mission was redesignated AS‑201 (Apollo‑Saturn 201).
According to the schedule, several flights were planned after AS‑202, at least up to AS‑209. The next spacecraft to reach the launch pad was AS‑204, intended to be the first crewed flight. However, the launch was repeatedly delayed due to various issues, mainly with the Environmental Control System (ECS). The situation worsened after a fuel tank explosion destroyed the service module of another spacecraft. Before the cause of the failure was found, NASA’s work had fallen heavily behind schedule, and funding problems deepened the difficulties. On 27 January 1967, during routine training inside the AS‑204 capsule, a fire broke out and three astronauts lost their lives. NASA designated this mission Apollo 1.
After an intensive investigation, it was decided that the program would continue once a new version of the spacecraft, Apollo Block II, was delivered. Following the Apollo 1 tragedy, the entire schedule and flight designation system were changed. The names of subsequent missions were simplified, and all flights using spacecraft mock‑ups, as well as the AS‑203 test, which did not use either a mock‑up or a real Apollo, were omitted from the numbering. Only the tests with a real spacecraft (AS‑201 and AS‑202) and Apollo 1 were taken into account, and the next mission was named Apollo 4. This was to be the first launch of Saturn V.
In April 1968, Apollo 6 was launched. Most of the mission’s objectives were achieved, and NASA proceeded to prepare for crewed missions.
Between 27 May and 14 November 1968, NASA conducted intensive tests at the Manned Spacecraft Center (MSC) in Houston. Command modules and LTAs were placed in huge vacuum chambers. The Apollo spacecraft was subjected to extreme temperature differences similar to those it would encounter in space. Without leaving Earth, the astronauts faced the dangers that might occur in outer space. The exercises involved Joe Engle (who did not fly on Apollo missions but later commanded Space Shuttle missions), Vance Brand (who took part in the Apollo–Soyuz mission), and Joe Kerwin (participant in the Skylab program), as well as US Air Force pilots Turnage Lindsay, Lloyd Reeder, and Alfred Davidson. Work on the lander was carried out by James Irwin (Apollo 15), Grumman test pilots Gerald Gibbson and Glennon Kingsley, and US Air Force pilot Joseph Gagliano. The success of these tests made it possible to accelerate the program.
After the entire system was checked in the Apollo 9 mission, the “dress rehearsal” was assigned to Apollo 10. Thanks to this mission, a huge amount of new information was gathered. This flight concluded the Apollo test program. Not all faults were eliminated (which caused the failure of the Apollo 13 mission). The operational phase of the program then began, which proved successful: during six missions, twelve American astronauts stood on the surface of the Moon and returned safely to Earth.
The launch of Apollo 11 took place on 16 July 1969 from the Spaceflight Center at Cape Canaveral (at that time officially Cape Kennedy). The beginning of the Apollo 11 flight was spent in Earth orbit, after which it set out on a journey of 384,400 km. Because the lunar module was located beneath the crew module, a maneuver was carried out in which the lunar module was temporarily detached, the rest of the spacecraft was rotated 180°, and the lander was re‑docked, now positioned at the front. After three days, Apollo 11 entered lunar orbit. Armstrong and Aldrin moved into the lunar module, which was detached and began its historic landing. The astronauts landed on the Moon on 20 July 1969. Shortly afterward, Neil Armstrong sent a joyful message back to Earth – “The Eagle has landed.”
When, on 21 July 1969 at 02:56 UTC, Armstrong stepped down the ladder and set foot on the dust‑covered surface of the Moon, he spoke words that went down in history: “That’s one small step for man, one giant leap for mankind.” Malicious commentators point out that an emotional Armstrong forgot one word, which made the whole phrase lose its intended meaning: instead of “It’s one small step for a man, but one giant leap for mankind,” he said “It’s one small step for man,” so that the sentence in fact meant “it’s a small step for mankind, but a great leap for mankind.” NASA explained that the sentence had been complete and that the missing word could not be heard because of interference on the communications link. In 2006, Peter Ford, a computer specialist from Australia, demonstrated that Armstrong had in fact uttered the unlucky “a.”
Then Aldrin stepped out, and the two astronauts conducted scientific experiments, planted the American flag, and collected 21.7 kilograms of rocks, sand, and dust. The samples brought back by Apollo 11 were collected in four phases. After stepping onto the surface of the Moon, Armstrong gathered a few rock fragments into a plastic bag. These “contingency samples” provided a small amount of lunar material in case the mission had to be aborted suddenly and the crew forced to return to Earth early. A little later, he used a scoop to collect a larger quantity of lunar material into a metal container. Next, he collected “documented samples,” consisting of objects carefully selected for their geological value. Armstrong recorded notes and photographed the location and position of these minerals. Then samples were taken from beneath the lunar surface using special tools. After splashdown of Apollo 11, the samples were transported by two helicopters to Johnston Island, then by two airplanes to Houston, and finally by car to the Lunar Receiving Laboratory (LRL). Initial examinations were carried out by a special Preliminary Examination Team (PET) at the Manned Spacecraft Center in Houston, Texas. The samples were made available to 106 scientists in the United States and 36 researchers from eight other countries. They also placed a plaque reading: “Here men from the planet Earth first set foot upon the Moon. July 1969. We came in peace for all mankind.” After 21 hours and 36 minutes spent on the Moon, the astronauts returned to the command module, where Michael Collins was waiting for them. The journey back went smoothly. On 24 July 1969, Apollo 11 splashed down in the Pacific Ocean, 1,460 km southwest of the Hawaiian Islands and 21 kilometers from the waiting aircraft carrier USS Hornet.
Because of worsening weather, the landing site had been shifted by 400 km. At 195 hours and 7 minutes into the mission, the rescue team made visual contact with the capsule. The recovery operations differed from those of previous flights, because it was considered necessary to subject the lunar astronauts to biological quarantine. Therefore, divers dropped from a helicopter first handed the crew special biological isolation suits, and only after they had put them on were they hoisted into the helicopter cabin. At the same time, the cabin was disinfected. After transfer to the aircraft carrier Hornet, the lunar astronauts immediately entered a special quarantine unit (Mobile Quarantine Facility – MQF), in which they were transported to the Hawaiian Islands. At Ford Island, the container was loaded onto a C‑141 aircraft. The plane delivered the crew to Ellington Air Force Base in Texas, from where the container was transported to the space center in Houston, Texas, where they moved into a permanent quarantine facility. The quarantine lasted until 11 August and, as expected, produced a completely negative result. The Apollo 11 command module is now on display at the National Air and Space Museum in Washington, D.C.
After the Apollo 11 mission, another five crewed spacecraft landed on the Moon. The last mission took place in December 1972 (Apollo 17). Since then, no one has landed on the Moon.
