Space Stations were man-made habitats meant for housing people in space. As time went on, people were staying in space stations for longer.
Space stations were first designed in the Soviet Union after they lost the Moon race. Their first was Salyut 1. The first space station of the Salyut program, Salyut 1 was built to test whether humans could for longer than previously occurred. But to stay in orbit, it could not use a Soyuz spacecraft. Instead, Salyut 1 used a jet pack. Later Salyut space stations would use thrusters and gyroscopes to stay in orbit. Meanwhile, NASA built its own space station called Skylab in 1973. Skylab was meant to do more intensive experiments on human survival in space. This required constant communication with Houston. Communication airplanes were used for that purpose. After the last manned mission to Skylab, the United States and the Soviet Union decided to work together on a project to bring peace. The Apollo-Soyuz Test Project was the first US-Soviet (Russian) space mission. But there was a problem. The atmospheres of both spacecraft were incompatible. The Apollo Command Module used pure oxygen at the atmospheric near the top of Mt. Everest. The Soyuz used normal air at sea level. The Apollo designers came with a method to prevent the bends by using a chamber which allowed the astronauts to acclimatize to atmosphere in the Soyuz craft. In later space stations, all modules would have the same atmosphere. The Soviet Union built the next big space station by themselves in 1986. The Mir space station was the first space station built in space itself. The spacesuits worn by the cosmonauts were equipped with jet packs that replaced conventional umbilical cables. After the collapse of the Soviet Union, the Russians allowed the US Space Shuttle to dock at Mir. In 1998, work began on the International Space Station. Every major space agency was involved including NASA and Roscosmos. The parts of the space station were assembled by robotic arms. Also, the hull was designed to protect from space debris. The hull consisted of two thin layers of steel. The inner layer was also protected with kevlar. When the International Space Station was completed, it was big success. The next step in the evolution of the space station was coming.
Space stations continued evolving as time went on. The next step in space station evolution was space hotels.
Tech Level: 10
Space tourism started with suborbital spaceflights. Later on, orbital spaceflights started occurring as well. Before long, space stations were becoming space hotels. Private citizens could spend a few days in zero gravity. Some early space hotel designs were like conventional space stations. There were four main components to a space hotels. They were a power plant, a life support and maintenance module, a section for crew and passenger accommodations, and a space to play. Unlike with the International Space Station, the accommodations had to be partitioned for privacy. The solution was to make that section modular. This helped accommodate singles, couples, and families. Space hotels were for tourism. And new innovations came along. One innovation was around not long after the Space Shuttle was retired.
Inflatable Space Station Modules
Tech Level: 10
As a matter of fact, the first space hotel was also the most innovative. The Bigelow Commercial Space Station, nicknamed Skywalker, was the first space station to use inflatable modules. The shells of these modules were a foot thick. They were made 20 layers of foam, kevlar, nomex, nextel, etc. This hull could protect against not only space debris and micrometeoroids but also cosmic radiation. When deflated, the diameter would only be a certain size, but once inflated, the dianeter would expand to an even larger size. This gave people more space to move around. Of course, inflatable space station modules were not the only concept coming off the drawing board. Another was born out of the Space Shuttle itself.
Tech Level: 10
The external fuel tank on the Space Shuttle was the only part of the shuttle that was not reusable. However, they were also perfect for space stations. External fuel tanks were ten stories high and had 50,000 cubic feet of volume. Also, the reinforced structure of the external fuel tank made it launch-proof and vacuum-proof. They made good space stations. However, after the Space Shuttle was retired, this seemed like a dead end. Then, unexpectedly, the Space Shuttle program with a new purpose: toe place external fuel tanks into orbit. Discovery, Atlantis, and Endeavor were thrust back into service in the 2020s to put external fuel tanks into space. Twelve external fuel tanks were placed in orbit around Earth. After that, the Space Shuttles were retired for good. The external fuel tanks were then sold to space hotel companies who converted them into space hotels. These tank stations made good space hotels. However, by the mid-21st century, space tourism was changing everything.
Tech Level: 10-11
During the mid-21st century, space hotels became more elaborate. The novelty of living in microgravity attracted many adventurers. Zerovilles were large stations or hundreds of tightly-knit smaller stations. They could hold hundreds or even thousands of people for a week or more. By that point, environmental systems had advanced to the point that they could accommodate zerovilles. Large, open spaces were all over these zerovilles. Entertainment productions could be done here. They could used in sports with artificially-generated air currents. Artificial forests were also created, the like of which was never seen on Earth. By the late 21st century, zerovilles also became retirement communities for elderly people with uncurable ailments, those these would eventually become obsolete. While zerovilles were good tourist attractions, future human habitation of space required gravity, so that muscle and bone did not waste away. This led to spinning modules on many space stations.
Tech Level: 11
(Note: For more information on this technology, see Spin Gravity Habitats)
The first space stations to use spin modules were not huge and elaborate like zerovilles. The spinning resulted in centripetal acceleration which created pseudo-gravity. The center axis was always 0 G. Towards the outer walls, the pseudo-gravity could be at any level, but it was usually 1 G. Many systems were placed in the center axis. These included docking systems, cargo transfer facilities, and primary maintenance hubs. Maintenance could best be done at 0 G. However, there was a problem. A single spin module would end up drifting in unwanted directions. The solution was to have modules that rotated in opposite directions. This led to wheel stations.
Tech Level: 11
To optimize useful space without dangerous changes in gravity, wheel space stations were the best bet. This solved the rotational progression because the wheels rotated in opposite directions. This allowed for a permanent manned presence in space. It was possible for humans to work in relative comfort for months or even years. Eventually, this led to space colonies.