Space Station - astronomy.

Space Station - astronomy. I INTRODUCTION Space Station, any facility that enables humans to live in space for long periods of time. Space stations are used as laboratories where scientific and engineering experiments are conducted and as servicing centers where spacecraft can be repaired, upgraded, or even constructed. Space stations are expected to one day act as spaceports where spacecraft can pick up and deliver people, cargo, and fuel on the way to or returning from distant destinations, such as Mars. II LIVING IN SPACE Space stations require regular visits by spacecraft from Earth to deliver supplies. Some supplies are needed to help the space station complete its mission and may include new experiments, satellites, or fuel for rockets. Other supplies, such as replacements for worn out or broken parts, enable the station to continue operating. The space station's life-support system, the technology that provides a comfortable internal environment in the space station, must be supplied with oxygen, water, and food. These supplies are ferried from Earth on a regular basis. An average human needs about 630,000 cu cm (about 38,000 cu in) of oxygen, about 2 l (about 0.5 gallons) of water, and about 500 g (about 1 lb) of dry food each day. Together, the oxygen, water, and food for a single person for one day has a mass of about 3.4 kg (about 7.5 lb). The life-support system must also remove the carbon dioxide and water that humans breath out, and remove the fluid and solid waste they produce. Simple space stations with open-loop systems need all of the food, water, and oxygen delivered regularly and they discard all of the waste. More advanced, closed-loop space stations recover oxygen from carbon dioxide and recycle the water. This reduces the supplies that must be brought from Earth to keep the crew alive. III HISTORY A space station was first proposed by Russian scientist Konstantin Tsiolkovsky at the beginning of the 20th century. He envisioned large, cylindrical living quarters that would rotate to provide artificial gravity. Because these spacecraft would be the site where other spacecraft would stop and refuel, Tsiolkovsky called them stations. The first space station was the Salyut 1, launched by the Union of Soviet Socialist Republics (USSR) in April 1971. Salyut 1 was a simple station with an open-loop lifesupport system and was launched fully assembled. It was the first in a series of nine stations that were all based on the same structure, but became increasingly sophisticated. Later Salyut stations carried more electrical power, more computers, and some closed-loop life-support systems. Salyut 6 and 7 also had two docking ports, which allowed both a piloted module carrying a replacement crew and an unpiloted, automated supply-delivery vehicle to dock to the station at the same time. These later Salyut stations also demonstrated the capability of assembling larger stations while in orbit by connecting separately launched modules together. The United States Skylab space station was launched in 1973. Launched fully assembled, its mass (75 metric tons) was nearly four times that of Salyut 1. Skylab had open-loop life-support systems and was reliant upon supplies that were on board when it was launched. Skylab hosted three crews between 1973 and 1974 before reentering Earth's orbit and disintegrating in 1979. The experience that the Soviet space program gained from Salyut was used in the design of the first permanently manned station, called Mir. The core module of Mir was launched in 1986. Mir was assembled from six modules that were launched separately and docked to the core module. Mir had several closed-loop life-support systems and could support a permanent crew of three astronauts. Mir crews were delivered using the Soyuz spacecraft and supplies were delivered by an unpiloted version of Soyuz, called Progress. Progress can only carry about 3 metric tons of supplies. In the 1990s, following the dissolution of the USSR, the U.S. space shuttle became Mir's main supply vehicle because the aging space station needed more supplies than ever and Russia lacked funds for the necessary Progress missions. The space shuttle has a much larger capacity than the Progress freighters. It provided supplies capable of sustaining large crews and more intensive scientific experiments. Shuttle/Mir missions stopped in 1998, when the United States began focusing on other projects. Russian and European astronauts continued to visit the station, using Soyuz and Progress spacecraft for transportation and supplies. Russia allowed the station to fall out of orbit and crash into the Pacific Ocean in March 2001. In 1984 the U.S. National Aeronautics and Space Administration (NASA) announced a new program to establish a permanent space station, called Freedom. In 1994 the project was combined with the Russian Mir 2 project to produce the International Space Station (ISS). In addition to the main station, laboratory modules are being provided by the European Space Agency (ESA) and Japan. Canada is providing the Mobile Servicing System, which comprises a robotic arm called the Canadarm2; the Mobile Base System, which is a mobile work platform that moves along the length of the station; and the Special Purpose Dexterous Manipulator, a robot designed to perform delicate assembly tasks. Construction of ISS began in 1998 with the launch of a Russian-built module. The first of the permanent crews, composed of one American and two Russians, arrived at the station in November 2000. When completed, ISS will be 108.5 by 88.4 m (356 by 290 ft), will have a mass of about 450 metric tons, and will be able to support a permanent crew of up to seven people. ISS will be used mostly as an orbiting laboratory. There will be six separate pressurized laboratories for the crew to work in, as well as extensive facilities for experiments to be mounted on the outside for direct exposure to space. Currently NASA is using the space station primarily to understand the effects of long-term spaceflight on the human body. Contributed By: Christopher Mark Hempsell Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.