Other Free Encyclopedias » Science Encyclopedia » Science & Philosophy: Adam Smith Biography to Spectroscopic binary » Manned Spacecraft - Ongoing Debate: Crewed Vs. Uncrewed Flight, Overview, One-person Crewed Spacecraft, Two- And Three-person Spacecraft - Technical requirements of crewed spacecraft

Manned Spacecraft - Soyuz And Apollo

module moon lunar surface

The Voskhod and Gemini programs each lasted for about two years, to be replaced, in turn, by spacecraft designed to carry humans to the Moon. These programs were known as Soyuz ("Union") in the Soviet Union and Apollo in the United States. At an early stage, the Soviets appear to have abandoned the goal of placing humans on the Moon, and redesigned the Soyuz instead as an orbiting space station. The Soyuz spacecraft, a version of which is still used today by the Russian space program, consists of three primary components: the reentry vehicle, the orbital module, and the service module.

The reentry vehicle is designed to hold crew members during take-off, orbital flight, descent, and landing. It has an approximately bell-shaped appearance and contains the controls needed to maneuver the spacecraft. The orbital module contains the living and working quarters used by cosmonauts while the spacecraft is in orbit. A docking system is provided at the front end of the orbital module. The service module contains the fuel and engines needed for maneuvering the spacecraft while it is in orbit.

The first test of the Soyuz spacecraft took place in April, 1967, ending in disaster: cosmonaut V. M. Komarov was killed when his parachute failed. A second Soyuz accident occurred on June 30, 1971, when a pressure valve in the vehicle apparently failed to close during descent. Air leaked out of the spacecraft and all three Soviet cosmonauts suffocated before their ship reached ground. Blame for this accident was later placed on the eagerness of Soviet politicians to put a three-man team into space before a vehicle suitable for such a flight was available. Because of crowded conditions in the Soyuz cabin, the three cosmonauts were unable to wear the space suits that would have prevented their deaths. For subsequent Soyuz flights, the spacecraft was redesigned to permit the wearing of space suits. The space needed for this modification meant, however, that the vehicle could carry only two passengers.

The Apollo spacecraft consisted of three main parts: the command module, the service module and the lunar module. The complete vehicle was designed with the objective of carrying three men to the Moon—it was assumed without debate that the astronauts would be men—allowing one or more to walk on the Moon's surface and to carry out scientific experiments, then returning the crew to the Earth.

The Apollo command module was a conical spacecraft in which the crew lived and worked. It was about 10 ft (3 m) high and nearly 13 ft (4 m) wide, with a total volume of about 210 cubic ft (6 cubic m). The service module had a cylindrical shape with the same diameter as the command module and roughly twice its length. The service module held the propulsion systems needed for maneuvering in orbit, electrical systems, and other subsystems needed to run the spacecraft in space.

The lunar module carried two astronauts from lunar orbit to the Moon's surface. One part of the lunar module, the descent stage, was used only during descent, and was left on the Moon. The ascent stage of the lunar module rested on top of the descent stage and was used to carry the two astronauts back to the command module, which was waiting in orbit around the Moon with one astronaut aboard, at the end of their stay on the Moon.

The Apollo series involved a total of 11 crewed flights conducted over a period of four years between 1968 and 1972. Not all of these flights left Earth orbit or sought to land on the Moon; several flew orbits around the Earth or Moon to test equipment. In December 1968, Apollo 8 became the first crewed spacecraft to travel to another world, orbiting the Moon before returning to Earth. The climax of the Apollo mission series occurred on July 20, 1969, when astronauts Neil A. Armstrong and Edwin E. ("Buzz") Aldrin, Jr., landed on the basaltic plain known as the Sea of Tranquillity, walked on the Moon's surface, and collected samples of lunar soil and rock. Five more landings on the Moon's surface were accomplished before the Apollo program was ended, all placing two men on the surface while a third remained in orbit. During the last three landings on the Moon's surface, astronauts were able to use a lunar roving vehicle (LRV) for moving about on the Moon's. The LRV was about 10 ft (3 m) long and 6 ft (1.8 m) wide, with an Earth weight of 460 lb (209 kg). It was carried to the Moon inside the descent stage of the lunar module in a folded position and then unfolded for travel on the Moon's surface.

Like the Soviet space program, the American space effort has had accidents. The first of these occurred on January 27, 1967, during tests for the first Apollo flight. Fire broke out in the command module of the Apollo spacecraft, which had been filled with a pure oxygen atmosphere, and three astronauts—Roger Chaffee, Virgil Grissom, and Edward White—died. This disaster caused a delay of 18 months in the Apollo program while engineers restudied and redesigned the Apollo spacecraft to improve its safety. The loss of the space shuttles Challenger and Columbia will be discussed further below.


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