Mir (Russian: peace or world) was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. Mir was the first modular space station and was assembled in orbit from 1986 to 1996.
At the time it was the largest and most massive artificial satellite in orbit, succeeded by the International Space Station (ISS).
The station served as a microgravity research laboratory in which crews conducted experiments in biology, human biology, physics, astronomy, meteorology, and spacecraft systems.
The station was launched as part of the Soviet Union's manned spaceflight programme effort to maintain a long-term research outpost in space, and following the collapse of the USSR, was operated by the new Russian Federal Space Agency (RKA).
Mir was the first continuously inhabited long-term research station in orbit and held the record for the longest continuous human presence in space at 3,644 days, until it was surpassed by the ISS on 23 October 2010.
It holds the record for the longest single human spaceflight, with Valeri Polyakov spending 437 days and 18 hours on the station between 1994 and 1995.
Mir was occupied for a total of twelve and a half years out of its fifteen-year lifespan, having the capacity to support a resident crew of three, or larger crews for short visits.
Mir was de-orbited in March 2001 after funding was cut off. The cost of the Mir programme was estimated in 2001 as $4.2 billion over its lifetime (including development, assembly and orbital operation).
Reference: Wikipedia - Mir | Gunter's Space Page - Mir | Encyclopedia Astronautica - Mir
The Salyut Programme (Russian: "salute" or "fireworks") was the first space station programme, undertaken by the Soviet Union. It involved a series of four crewed scientific research stations and two crewed military Almaz reconnaissance stations over a period of 15 years, from 1971 to 1986.
Salyut was used to carry out long-term research into living in space and a variety of astronomical, biological and Earth-resources experiments.
Salyut 1, the first station in the program, became the world's first crewed space station.
Mir was the next stage in the Soviet Union's space station programme.
Reference: Wikipedia - Salyut Programme
Mir consisted of seven pressurised modules and several un-pressurised components. Power was provided by several photovoltaic arrays attached directly to the modules.
The first module of the station, known as the core module or base block, was launched in 1986. The six other modules were launched between 1987 and 1996.
All of the components were launched, un-piloted, on Proton rockets except for the docking module, which was installed by US Space Shuttle mission STS-74 in 1995.
The station was maintained at an orbit between 296 km and 421 km altitude and travelled at an average speed of 27,700 km/h, completing 15.7 orbits per day.
Refer: Components Main Page
A space station is a Spacecraft built to fly in a permanent, fixed 'Low Earth Orbit'. For example Mir was maintained in a near circular orbit with an average perigee of 354 km and an average apogee of 374 km . At this altitude there is still a small amount of atmosphere, sufficient to cause drag and slow the station down. As it slows the station loses altitude and slows even more. Eventually it would fall out of orbit and be destroyed.
Mir's altitude boost was generally performed by Progress resupply vessels, although during the Shuttle-Mir programme the task was performed by US Space Shuttles. Prior to the arrival of Kvant-1 module, the engines on the core module could also accomplish the task.
A station is also designed to accommodate a crew who operate and maintain it. The crew must be kept supplied with food, water, oxygen and maintenance items. Mir had the capacity to support a resident crew of three, or larger crews for short visits.
Originally space stations were envisaged as transfer facilities. Earth to orbit shuttles would deliver people to the station and they would then be transferred to lunar or inter-planetary craft for travel throughout the solar system.
For example, in Arthur C. Clarke's "2001 A Space Odyssey", space planes transported people from Earth to a large wheel shaped space station. People were then transferred to shuttles which flew from the station to the moon.
Unfortunately space technology has not progressed to this stage yet. The space stations built so far have been designed with the primary purpose of research.
Mir is too large to be built on Earth and launched into orbit. The only practical method, at present, is to launch manageable sized components into orbit and assemble them there.
Building in orbit also allows the components to be lighter because they are not subject to the full force of gravity found on Earth.
Extra Vehicular Activities (EVA's) or spacewalks are often required to finalize installation.
The orbital assembly of Mir began on 19 February 1986 with the launch of the base block for the entire Mir complex, the core module, or DOS-7. This was carried into orbit on a Proton-K rocket. Four modules were added later to the Mir complex. These were launched independently on their own Proton-K rockets and chased the station to dock automatically.
The other two expansion modules followed different procedures. One had no engines of its own and used a tug based on the TKS spacecraft to reach the station. The other was launched aboard Space Shuttle Atlantis during STS-74.
Various other external components, including three truss structures, several experiments and other un-pressurised elements were also mounted to the exterior of the station by cosmonauts conducting a total of eighty spacewalks over the course of the station's history.
The station's assembly marked the beginning of the third generation of space station design, being the first to consist of more than one primary spacecraft. First generation stations such as Salyut 1 and Skylab had monolithic designs, consisting of one module with no resupply capability. Second generation stations Salyut 6 and Salyut 7 comprised a monolithic station with two ports to allow consumables to be replenished by cargo spacecraft such as Progress.
The capability of Mir to be expanded with add-on modules meant that each could be designed with a specific purpose in mind thus eliminating the need to install all the station's equipment in one module.