Apollo Program - U.



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Apollo Program - U.


Aperçu du corrigé : Apollo Program - U.

Publié le : 2/5/2013 -Format: Document en format HTML protégé

Apollo Program - U.

Apollo Program - U.S. History.


Apollo Program, American manned lunar-space program designed to land an astronaut on the Moon and return him safely to Earth, as well as to overtake the former
Soviet Union in the race to dominate space exploration. Conducted between May 1961 and December 1972 by the National Aeronautics and Space Administration
(NASA), the program successfully landed Neil Armstrong--the first person to walk on the Moon--and 11 other astronauts on the Moon. The program included 12
manned missions: 2 into Earth orbit (Apollo 7 and 9); 2 into lunar orbit (Apollo 8 and 10); 3 lunar landing missions (Apollo 11, 12, and 14); and 3 lunar exploration
missions (Apollo 15, 16, and 17), which involved extended stays on the Moon's surface and more in-depth scientific exploration. One mission was lost during a test on
the launch pad (Apollo 1), and one mission returned to Earth without making a scheduled lunar landing (Apollo 13). Following the Apollo program, Apollo spacecraft were
used to shuttle astronauts to and from the Skylab space station, and an Apollo spacecraft docked with the orbiting Soviet spacecraft Soyuz 19 in the Apollo-Soyuz Test
The Apollo program was initiated by United States President John F. Kennedy on May 25, 1961. It was preceded by the manned Gemini program, which engineers used
to develop the techniques that would be needed for the ambitious trip to the Moon, and the unmanned Surveyor Program, which scientists used to probe the lunar
surface. At the peak of Apollo preparations in 1965, NASA employed 36,000 civil servants and 376,700 contractor employees, and had a yearly operating budget of
$5.2 billion. Between 1961 and 1973, NASA spent approximately $25.4 billion on the Apollo missions.
During the same time period, the Soviet Union scheduled a manned mission to circle the Moon (Zond 7)--just three weeks before Apollo 8. This mission was postponed
and the spacecraft was later launched unmanned. The Soviets continued to develop and test their one-man Lunar Lander spacecraft in Earth orbit through August
1971, but a Soviet cosmonaut never reached the Moon.



Each manned Apollo mission consisted of two spacecraft: the Command and Service Module (CSM) designed for orbital and reentry operations; and the Lunar Module
(LM) designed for lunar landing, surface operations, ascent from the Moon, and rendezvous with the CSM. The exceptions were Apollo 7 and 8, which flew the CSM only.
The CSM comprised the command module, with the crew compartment and the reentry heat shield, and the service module, with the major support systems and
consumables (such as propulsion systems, electrical power, food, and water). The LM comprised the descent stage, for landing and delivery of the lunar-surface
equipment, and the ascent stage, with the crew compartment and independent systems for ascent from the Moon's surface and rendezvous with the CSM.
Apollo missions used a crew of three astronauts. During launch, all three astronauts were in the CSM. After leaving Earth orbit, the crew separated the CSM from the LM
and the part of the launch vehicle surrounding the LM, then maneuvered the CSM to dock with the LM to extract the LM from the launch vehicle so that the crew could
transfer between the two craft. After three days' transit time to the Moon, the CSM and LM entered into lunar orbit. Two astronauts then transferred to the LM,
separated from the CSM, and descended to the lunar surface. The third astronaut continued to operate the CSM in lunar orbit.


Launch System

The launch vehicle used for lunar missions was the Saturn V rocket designed specifically for Apollo craft. The Saturn launch vehicle family and the design of its support
facilities were derived from technology developed by rocket engineer Wernher von Braun and his team at Peenemünde, Germany, during World War II. Von Braun
brought his work and his team to the United States in 1945.
The Saturn V consisted of three stages used in sequence to boost spacecraft into Earth orbit and on toward the Moon. The CSM and LM were mounted separately, in
tandem, on top of the Saturn rocket system. At liftoff, the entire launch vehicle (including spacecraft) was 109 m (363 ft) high; it weighed 2.8 million kg (6.3 million lb);
and the five Saturn first-stage engines generated 3.5 million kg (7.7 million lb) of thrust. During the Apollo program, 12 Saturn V rockets were launched from the
Kennedy Space Center at Cape Canaveral, Florida, and all were successful.


Lunar Surface Systems

After landing, the LM became a habitable lunar base serving as living quarters, communications center, storage facility, equipment carrier, and supply center for food
and water. The cylindrical LM crew compartment was less than 2.4 m (8 ft) in diameter and only 1 m (3.3 ft) deep. The lifetime and capacity of this lunar base was
increased from less than two days for the first three lunar landing missions to over three days for the final three lunar exploration missions.
The performance of the astronaut Extravehicular Mobility Unit (EMU) was a key element in the success of Apollo. The EMU consisted of the astronaut space suit and the
Portable Life Support System (PLSS). The EMU provided oxygen and pressure to sustain life in the vacuum of space; it protected the astronaut from thermal, radiation,
and optical effects as well as meteorite impact; and it provided sufficient mobility and dexterity to enable the astronaut to perform useful work on the lunar surface. The
PLSS was recharged with oxygen and cooling water from LM supplies after each outside excursion, known as an Extra Vehicular Activity (EVA). On the final three lunar
exploration missions, the PLSS life-support capability for a single excursion was more than doubled to over seven hours.
Lunar surface equipment included a variety of cameras, geology tools, rock and soil sample containers, several individual science experiments, and the multidiscipline
Apollo Lunar Surface Experiments Package (ALSEP). ALSEPs measured topological and geophysical characteristics of the Moon and were set into place and left behind by
the astronauts. They were nuclear powered and designed to operate for at least five years--several lasted much longer. The final three missions (Apollo 15-17) also
carried the two-man Lunar Roving Vehicle (LRV) with additional geology tools, experiments, and sample containers. The LRV vastly increased the range and capability of
lunar surface exploration.


Support Facilities

The success of Apollo also was dependent on a number of facilities on Earth. Foremost among these were the test and qualification facilities for spacecraft, launch
vehicles, and the EMU; simulators and trainers to prepare the astronauts for the mission; the launch complex at Cape Canaveral; the worldwide tracking and
communications network; and the Mission Control Center in Houston.



The Lunar Orbit Rendezvous (LOR) technique used for the Apollo missions consisted of launching the spacecraft into a stable orbit around Earth; setting a path toward
the Moon; moving the spacecraft into orbit around the Moon; landing the LM on the lunar surface; taking off in the LM from the lunar surface and returning to the

Moon's orbit; rendezvousing and docking with the CSM; and finally, setting a course home to Earth. On return to Earth, the spacecraft was slowed by drag from Earth's
atmosphere and by parachutes (just before splashdown), before landing in the ocean. The transit time to and from the Moon was approximately three days each way.
Depending on the specific mission, the time in lunar orbit ranged from less than one day for Apollo 8 to over six days for the final three missions, and the time on the
lunar surface ranged from less than one day for Apollo 11 to over three days for Apollo 15, 16, and 17.


Apollo Test Missions

A total of 16 unmanned Apollo missions were flown between October 1960 and April 1968. The objective of these missions w...

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