Introduction
S
pace 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.
Living in space
S
pace stations require regular visits by spacecraft from the 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 the 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 the earth to keep the crew alive.
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 Soviet Union in April 1971. Salyut 1 was a simple station with an open-loop life support 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.
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 has several closed-loop life-support systems and can support a permanent crew of three astronauts. Mir crews are delivered using the Soyuz spacecraft and supplies are delivered by an unpiloted version of Soyuz, called Progress. Progress can only carry about three metric tons of supplies. In the 1990s 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 live aboard the station, using Soyuz and Progress spacecraft for transportation and supplies. Russia plans to allow the station to fall out of orbit and burn up in Earth's atmosphere before 2010.
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 ten nations affiliated with the European Space Agency and Japan. Canada is providing a robotic arm and a servicing center, a platform for the robotic arm.
Construction of ISS began in 1998 with the launch of a Russian-built module. Construction is scheduled to continue until 2003, including at least 20 planned construction flights. Most of the construction will involve docking modules together, but there will also be some construction work performed by astronauts on space walks. When completed, ISS will be 108 by 81 m (354 by 266 ft), have a mass of about 400 metric tons, and support a permanent crew of six people.
ISS will be used mostly as an orbiting laboratory. There will be eight 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.
The Contents
Introduction