Requirements for human life are relatively easy to fulfill on a short-term basis. With a supply of oxygen, heat, water and food, humans can survive in space indefinitely. On the International Space Station, power is supplied by four huge solar arrays, food is brought onboard by shuttles and oxygen and water are generated and reclaimed by specialized modules in the station. Therefore, people can live (relatively) comfortably in space for short periods of time (usually less than six months).
Did you know? Astronaut Chris Hadfield will be the first Canadian to be Commander of the International Space station starting in March 2013.
The problem of living in space becomes considerably more complicated when considering long-term stays. One of the key issues faced by astronauts is bone loss. On Earth, our bones are constantly being reformed in response to mechanical stress (osteoporosis is a disease where this process breaks down leading to very brittle bones, usually in the elderly). In space, the lack of gravity means that there is no stress on bones, which leads to severe bone loss. Studies looking at this problem have shown that it takes more than five years for astronauts to recover from the bone loss incurred by a six month stay on the ISS.
Did you know? The longest stay in space was 438 days by cosmonaut Valeri Polyakov.
For a long-term stay in space, we would first need to establish artificial gravity. If you’ve seen 2001: A Space Odyssey, or read the novel Ender’s Game, you may be familiar with the idea of creating artificial gravity by rotating a cylindrical section of a spacecraft. Like most problems in space, it’s theoretically simple but very difficult in practice. Rotational acceleration would certainly produce artificial gravity, but if you rotate too fast your space station becomes an amusement park ride. Make your cylinder too small and gravity becomes stronger at your feet than it is at your head.
Did you know? On the International Space Station, salt and pepper come in liquid form, otherwise they would just float away!
There are other issues to consider as well, such as the psychological effects of being entirely confined to a space station for long periods of time. However, the good news is that companies like Virgin Galactic and Space Adventures are already making space tourism possible. Currently, these trips are obscenely expensive and limited to space flights, but I would expect to hear serious talk about space hotels in the next 20 or 30 years.