Apollo 11 and the quest to land humans on the Moon
--50th Anniversary of the First Moon Landing 
D. Indumathi, The Institute of Mathematical Sciences, Chennai

The journey to space
On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first person to fly in space. His capsule, called Vostok 1, completed one full orbit around the Earth on 12 April 1961. This was a great achievement for the Soviet Union after the failure of the Luna 1 unmanned moon mission in 1959. later, both Luna 2 and the American ranger 4 managed a crash-landing (or hard landing) on the moon. After this several Soviet and American moon missions attempted a soft landing on the moon by using rockets to brake the speed of the probe as it descends. 
In 1966 the USSR achieved the first soft landings and took the first pictures from the lunar surface during the Luna 9 and Luna 13 missions.  The photo shows the landing sites of both the Luna 8 crash landing and the Luna 9 soft landing. It was only in 1970 that the Soviets managed to successfully land a probe andd bring it back to the Earth. The Luna 16 probe had no humans on it, but used robotic devices to bring a soil sample back. Many more unmanned missions followed, both successful and unsuccessful. The rivalry between the Soviets and the Americans spilled over, and both considered conquering of space as the final frontier.

Human moon missions
It was with the beginning of the Apollo missions by the Americans that moon missions included human cargo. The first was that of Apollo 11, whose successful journey allowed two humans to set foot on the moon on 20 July, 1969, almost exactly 50 years ago. The Apollo programme allowed twelve humans (all men) to land on the moon. The first men to land on the moon were Neil Armstrong and Buzz Aldrin. After being launched into orbit by a Saturn V rocket four days earlier, the astronauts separated the spacecraft from the rocket and travelled for three days to enter the lunar orbit around the moon. Armstrong and Aldrin then moved into the Apollo Lunar Module called Eagle.

Apollo 11
Apollo 11 had three parts: a command module called Columbia with a cabin for the three astronauts, a service module which supported the command module with propulsion, electricity, oxygen, and water, and a lunar module called the Eagle which would actually land on the moon.
The picture shows Columbia in lunar orbit, photographed from the Eagle.  The second picture shows the Eagle in lunar orbit photographed from the Columbia. Perhaps selfies were not common then, but certainly photography was as popular then as it is now!
The lunar module had two parts, one for descent for landing the two astronauts on the moon and one for ascent which would take them back into the lunar orbit.
Armstrong became the first person to step onto the lunar surface six hours 39 minutes after landing on the moon, on July 21 at 02:56 UTC. Aldrin joined him 19 minutes later. The long time was because of the many check lists that they had to go through, including food packets and tools.  Remember that there is no atmosphere on the moon and gravity is very small, about 1/10th of that on Earth.
Eagle's hatch was opened at 02:39:33. Armstrong initially had some difficulties squeezing through the hatch with his portable life support system. He then descended a nine-rung ladder, activating his camera to show his descent.
At all times, all the vitals of the astronauts were being recorded. It turned out, expectedly, that some of the highest heart rates recorded from Apollo astronauts occurred during exiting and entering the module. You can imagine the feelings of the men, the first to set foot on the moon, and not knowing whether they would ever return home again.
They spent about two and a quarter hours together outside the spacecraft, and they collected 21.5 kg of lunar material to bring back to Earth. In order to bring back so much material, they had to leave behind a lot of waste matter which is still lying on the moon.
Armstrong's first step onto the lunar surface was broadcast on live TV to a worldwide audience. He described the event as "one small step for [a] man, one giant leap for mankind."
While still on the ladder, Armstrong uncovered a plaque mounted on the lunar module's descent stage bearing two drawings of Earth (of the Western and Eastern Hemispheres), an inscription, and signatures of the astronauts and President Nixon. The inscription read:
    "Here men from the planet Earth first set foot upon the Moon July
    1969, A.D. We came in peace for all mankind."
Aldrin joined Armstrong on the surface. He described the view with the simple phrase: "Magnificent desolation."
Command module pilot Michael Collins flew the command module Columbia alone in lunar orbit while they were on the Moon's surface. Armstrong and Aldrin spent 21 hours 31 minutes on the lunar surface at a site they named Tranquility Base before lifting off to rejoin Columbia in lunar orbit.
The picture shows a view of the Apollo 11 lunar module Eagle as it returned from the surface of the moon to dock with the command module Columbia. A smooth mare area is visible on the Moon below and a half-illuminated Earth hangs over the horizon. The lunar module ascent stage was about 4 meters across. Command module pilot Michael Collins took this picture just before docking at 21:34:00 UT, 21 July 1969.

Memorials
After more than two and a half hours on the lunar surface, the scientists left behind, in addition to the scientific instruments: an Apollo 1 mission patch in memory of astronauts Roger Chaffee, Gus Grissom, and Edward White, who died when their command module caught fire during a test in January 1967; two memorial medals of Soviet cosmonauts Vladimir Komarov and Yuri Gagarin, who died in 1967 and 1968 respectively; a memorial bag containing a gold replica of an olive branch as a traditional symbol of peace; and a silicon message disk carrying the goodwill statements by Presidents Eisenhower, Kennedy, Johnson, and Nixon along with messages from leaders of 73 countries around the world. 
Before returning in the Columbia, they discarded the lunar module, Eagle, and propelled Columbia back to Earth, and like most air travellers, slept most of the time during the return journey. They splashed down in the Pacific Ocean (as the safest way to re-enter) on July 24, after more than 8 days in space, packed into a small space leaving no room to walk or manouvre. But they had made history.

Other manned missions
Apollo 12 was the second to land on the moon, four months after Apollo 11. Commander Charles "Pete" Conrad and Lunar Module Pilot Alan L. Bean performed just over one day and seven hours of lunar surface activity while Command Module Pilot Richard F. Gordon remained in lunar orbit. 
However, Apollo 13 reached the moon but could not landd. The crew managed to return to Earth, but without completing their mission. Apollo 14 landed successfully, as also Apollo 15, 16, and 17. Apollo 17 was the last moon landing by humans, in Dec 1972. All the rocks collected over these missions were analysed for their age, mineral content, presence of water, and evidence of formation age of the moon. Not only that, the Apollo programme has been called the greatest technological achievement in human history, achieving many advances in technology, leading to over 1,800 spinoff products as of 2015.
But in spite of all that was learned about the Moon, the Americans could not sustain the cost of these missions. Instead, they truend to developing the Space Shuttle (a reusable spacecraft) and then the International Space Station (ISS). The ISS is a space station or habitable artificial satellite in low Earth orbit. The ISS programme is a joint project between five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada).  The ownership and use of the space station is established by intergovernmental treaties and agreements. Here the crew members conduct experiments in biology, human biology, physics, astronomy, meteorology, and other fields. It has been visited by astronauts from several countries and marks another area like the Earth's South Pole where international cooperation has resulted in turly global scientific understanding.

--Compiled from several sources; pictures from Wikipedia and NASA