APOLLO NASA

Apollo program
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Apollo program insignia

The Apollo program was a human spaceflight program undertaken by NASA during the years 1961–1975 with the goal of conducting manned moon landing missions. In 1961, President John F. Kennedy announced a goal of landing a man on the moon by the end of the decade. It was accomplished on July 20, 1969 by the landing of astronauts Neil Armstrong and Buzz Aldrin, with Michael Collins orbiting above during the Apollo 11 mission. Five other Apollo missions also landed astronauts on the Moon, the last one in 1972. These six Apollo spaceflights are the only times humans have landed on another celestial body.[1] The Apollo program, specifically the lunar landings, is often cited as the greatest achievement in human history.[2][3]

Apollo was the third human spaceflight program undertaken by NASA, the space agency of the United States. It used Apollo spacecraft and Saturn launch vehicles, which were later used for the Skylab program and the joint American-Soviet Apollo-Soyuz Test Project. These later programs are thus often considered to be part of the overall Apollo program.

The goal of the program, as articulated by President Kennedy, was accomplished with only two major failures. The first failure resulted in the deaths of three astronauts, Gus Grissom, Ed White and Roger Chaffee, in the Apollo 1 launchpad fire. The second was an in-space explosion on Apollo 13, which badly damaged the spacecraft on the moonward leg of its journey. The three astronauts aboard narrowly escaped with their lives, thanks to the efforts of flight controllers, project engineers, backup crew members and the skills of the astronauts themselves.

The program set major milestones in the history of human spaceflight. This program stands alone in sending manned missions beyond low Earth orbit. Apollo 8 was the first manned spacecraft to orbit another celestial body, while Apollo 17 marks the time of the last moonwalk and also the last manned mission beyond low Earth orbit. The major space exploration milestones leading up to the moon landing include:

* first sub-orbital flight (1942)
* first orbital flight (1957)
* first unmanned lunar mission (1959)
* first man in space (1961)
* first manned lunar mission (1968).
* first manned lunar landing (1969).

The program spurred advances in many areas of technology peripheral to rocketry and manned spaceflight. These include major contributions in the fields of avionics, telecommunications, and computers. The program sparked interest in many fields of engineering, including pioneering work using statistical methods to study the reliability of complex systems made from component parts. The physical facilities and machines which were necessary components of the manned spaceflight program remain as landmarks of civil, mechanical, and electrical engineering. Many objects and artifacts from the program are on display at various locations throughout the world, notably at the Smithsonian's Air and Space Museums.

Boosters

When the team of engineers led by Wernher von Braun began planning for the Apollo program, it was not yet clear what sort of mission their rocket boosters would have to support. Direct ascent would require a booster, the planned Nova rocket, which could lift a very large payload. NASA's decision in favor of lunar orbit rendezvous re-oriented the work of Marshall Spaceflight Center towards the development of the Saturn 1B and Saturn V. While these were less powerful than the Nova would have been, the Saturn V was still much more powerful than any booster developed before—or since.

[edit] Saturn V
Main article: Saturn V
The Saturn V rocket launched Apollo 11 and her crew on its journey to the Moon, July 16, 1969.
Saturn V diagram from the Apollo 6 press kit

The Saturn V consisted of three stages and an Instrument Unit which contained the booster's guidance system. The first stage, the S-IC, consisted of five F-1 engines arranged in a cross pattern, which produced a total of 7.5 million pounds of thrust. They burned for only 2.5 minutes, accelerating the spacecraft to a speed of approximately 6000 miles per hour (2.68 km/s).[22] During development, the F-1 engines were plagued by combustion instability—if the combustion of propellants was not uniform across the flame front of an engine, pressure waves could build which would cause the engine to destroy itself. The problem was solved in the end through trial and error, fine-tuning the engines through numerous tests so that even small charges set off inside the engine would not induce instability.[23]

The second stage, the S-II, used five J-2 engines. They burned for approximately six minutes, taking the spacecraft to a speed of 15,300 miles per hour (6.84 km/s) and an altitude of about 115 miles (185 km).[24] At this point the S-IVB third stage took over, putting the spacecraft into orbit. Its one J-2 engine was designed to be restarted in order to make the translunar injection burn.[25]

[edit] Saturn IB
Main article: Saturn IB

The Saturn IB was an upgraded version of the earlier Saturn I. It consisted of a first stage made up of eight H-1 engines and a second S-IVB stage which was identical to the Saturn V's third stage. The Saturn IB had only 1.6 million pounds of thrust in its first stage—compared to 7.5 million pounds for the Saturn V—but was capable of putting a command and lunar module into earth orbit.[26] It was used in Apollo test missions and in both the Skylab program and the Apollo-Soyuz Test Program. In 1973 a refitted S-IVB stage, launched by a Saturn V, became the Skylab space station.