What is an Orbital Space Colony?
An orbital space colony is a giant spacecraft big enough to live in. Orbital colonies will travel endlessly through space while the folks inside play, work, socialize, and (hopefully not too often) fight. Mankind has never built a space colony; the closest we've come is a series of space stations. A space station isn't a place to live, but rather a place to work. The difference between a space station and a space colony is the difference between a work camp and home. Living inside a space colony will, in many ways, be like living on Earth. People will have houses or apartments. They will go to work and to school. There will be shops, sports teams, concerts and movies. People will go to parties with their friends, just like on Earth. But there will be differences as well. Today we live on the outside of a planet. Earth is thousands of kilometers across, so big that it looks like we are living on a flat surface. Instead of living on the outside of a huge planet, space settlers will live inside very large spacecraft. Large enough to take a good walk, but not so big that it will look like you live on a flat surface. People will live on the inside of spheres, cylinders, and toruses (a donut shape). These shapes are ideal for space colonies because colonies must rotate to produce pseudo-gravity, and the main living areas must be equidistant from the axis of rotation so the 'gravity' doesn't change as you move around. Pseudo-gravity is necessary because space colonies have far too little mass to produce much real gravity, but something like gravity is needed for bones and muscles to stay strong. Since most colonies will only be a few kilometers across, the curve of the hull will be easy to see. Unlike Earth, however, which curves down, when you look around the neighborhood in a space colony the land will curve up.
There is another big difference. The air and water we need to live is recylced on a huge scale here on Earth, and we don't need to work too hard for that to happen. On a space colony, millions of times smaller than Earth, we will need to constantly monitor the air and water and take quick action if anything begins to go wrong. Here on Earth CO2 levels are rising and some are concerned that decades from now global warming will become a serious problem. On a space colony, rising CO2 levels will cause an immediate alarm and require fixing within hours to avoid the entire population suffocating. Every space colonist will be a rabid environmentalist by absolute necessity.
On a space settlement, recycling will be a way of life. Here on Earth many people feel we can use things and throw them away. There are plenty of materials all around us. On a space colony, every atom is precious. Nothing, except perhaps the most toxic of toxic wastes, will be thrown away. Everything will be endlessly recylced, especially water. Waste water won't go out to the sea. It will run to the outside where sunlight will sterilize the waste, and then everything will be recylced through the agricultural section.Agriculture will be different too. On Earth, huge farms take advantage of natural conditions to grow the food we need to live. On a space colony, there are no natural conditions. Food will be grown in small, carefully controlled rooms where conditions are kept perfect for the crops being grown. This will lead to very high yields so the area needed for agriculture will be far smaller than on Earth. Furthermore, plants in the agricultural modules will be integrated into the atmosphere maintenance systems since plants produce oxygen and consume CO2.
The further big difference will be low and zero-g recreation. On Earth, we always feel the pull of gravity and it's always the same amount (1g, the 'g' stands for gravity). On a rotating space colony, people just on the inside of the hull will feel a pull a lot like gravity and the amount will be 1g. However, as you go closer to the center of the colony the pull will gradually decrease until it's 0g right at the axis of rotation. This will be a lot of fun. Jumping 20 meters will be easy, even for the most out-of-shape colonists. Gymnasts and dancers will experience freedom of movement they could never have on Earth. New sports will be created to take advantage of freedom from gravity, and old sports will change to adapt to the new conditions. Baseball, American football, and basketball won't work very well in 0g, but they will still be played just inside the hull where 1g rules. However, soccer (called football outside the U.S.) can be easily adapted to 0g and we can expect some very exciting, and wild, 0g games.
No one has ever built a space colony, and it is sufficiently difficult that it will be many years before that happens. Mankind has, however, been building space stations for decades. Space stations aren't homes, they are work camps, like the ones used to to build the Alaska pipeline. Nonetheless, space stations are real today, so it's worth taking a look at what we've done.