Space habitats could offer the humankind an options to settle the space in the future. Space habitats would provide habitats for large number of people in the vast outer space. Space habitats could survive for a long periods of time without any external support.
In order for the space station to be able to provide living space for thousands or tens of thousands of people, it must be able to produce and recycle most of its resources. Also, it should be able to provide humans conditions, that they feel well mentally and physically.
Space habitats should be able to keep constant air pressure with breathable air. The atmosphere would probably consist nitrogen, oxygen and carbon dioxide, just like the atmosphere on Earth. The plants on the habitat would remove carbon dioxide and produce oxygen. The air should be cleaned by some other methods, too, as the plants can’t remove all the harmful substances.
Humans have some experience from building breathable atmosphere on a smaller scale. Submarines and current space stations use technologies, that could be also used on a larger space habitat. It is hard to estimate, however, how well these technologies would work on a larger scale with limited resources.
In order to thrive, the space habitat should be able to produce most of its food autonomously. Plants would create oxygen for the settlers, but also would be a source of food. One problem regarding the food production is the fertilizers, as large amounts of them would be needed. Some could be recycled, but external support would still be required. Also, when beginning the production, large amounts of mold are needed in the station.
According to studies, being in a low gravity environment causes harmful effects to humans. In order for the humans to be able to live in a space habitat for multiple years, the problem should be solved, for example by using centrifugal forces as a way to create artificial gravity. When the station is rotating, the rotation would provide a gravity that would feel quite natural. This requires that the station is large and the rotational speed is slow, to avoid any adverse effects.
In outer space, where the magnetic field of the Earth does not provide protection from space radiation, other protection is needed. Space radiation is very harmful to humans, to the problem of radiation should be solved. Protection could be built using lead or rocks, for example. However, it’s very expensive to move heavy objects to the station. In the future, artificial magnet field could be created with powerful magnet network, for example.
Pros and Cons
A space habitat has many good sides, when comparing to more traditional idea of surface habitats. The conditions on many surfaces are harsh because of cold temperatures or otherwise challenging reasons. However, we do have the most of the necessary technology for space habitats, unlike surface bases in hard conditions. Space habitat can be located in a position where sunlight would always be available, so energy wouldn’t be a problem, either.
The biggest problem regarding the space habitats is the immense amount of resources that is needed to build them. Practically thinking, it would be almost impossible to transport all the resources from the Earth, so the resources should be harvested from space. Resources could be collected from the asteroid belt or from planets, that are nearby the space habitats being built. In addition, resources should be efficiently recycled. However, it’s not possible to recycle everything, so the habitats should receive or they should be able to collect additional resources.
Types of Space Habitats
There are multiple ways to build a large scale space station. Most of them would be rotating stations, that would produce artificial gravity with the centrifugal force. With different plans, most of the problems with space habitats have been solved. There are, however, a few problems that still persist, such as the problem with space radiation.
Bernal Sphere is a proposed space habitat by British John Desmond Bernal, who came up with the idea as early as 1929. According to Bernal, space habitat would be a sphere with a diameter of over 15 kilometres, and it could house 30 000 people. Rotating habitat, filled with air, would provide artificial gravity, and it would allow the inhabitants to grow food and live life normally, as they would do in Earth.
Gerard K. O’Neill proposed a few changes to the station. According to O’Neill, the first station should be only 500 meters by diameter. This would allow its equator to have a artificial gravity as strong as on Earth. The smaller habitat would work as an testing environment, after which we could build larger stations.
According to O’Neill, the smaller station would be able to provide habitat for 10 000 people. The light would be reflected in it through windows and the crops would be grown in separate growing stations. Growing crops separately would allow more space for people. According to O’Neill, a sphere is a good options because of its ability to maintain constant air pressure and protecting it from space radiation would be inexpensive, compared to other options.
Stanford torus is a proposed plan to build a large scale space habitat. It could house as many as 140 000 people. As for its shape, it would resemble a donut, whose slow rotational speed would create an artificial gravity inside it. There have been multitude of different space station designs like this, but the plan for Stanford torus is the most complete.
The diameter of torus would be almost two kilometres. In the centre, there would be a docking station for space ships. It would rotate around its axis once per minute. The sunlight could be delivered equally to all parts of space station with mirrors. When being inside a torus, it would resemble a long valley that slowly raises on both directions. Part of the station would be reserved for crops, and other plants for living humans.
Building a Stanford torus would require an immense amount of resources. It would weight around 10 million tonnes. With current technologies, transporting the required materials from Earth would not be feasible. The resources required for building of torus could be harvested from the asteroid belt, for example.
O’Neill cylinder is a proposed space habitat by Gerard K. O’Neill. It would consist of two cylinders, that would rotate on opposite directions, therefore removing any gyroscopic effects that might turn the habitat to unfavourable positions. The rotation would provide artificial gravity to both cylinders. The amount of sunlight inside the cylinders could be optimized by rotating the station.
The part connecting the cylinders would allow space ships to dock. On the end of the each cylinder, there would be enough space for crops and. According to O’Neill, cylinders would be 8 kilometre long, but they could be even tens of kilometres.
Inside the cylinders there would be an atmosphere, whose pressure would be about the half of the pressure on Earth. Because of the high oxygen content, humans would be able to breathe it without problems. The cylinders would be large enough to have a weather and phenomena, such as clouds and rain. Because of the large size, possible break in a window wouldn’t cause catastrophic failure if the problem is fixed swiftly.
The atmosphere would be thick enough to stop most of the harmful space radiation. Other parts of the space station would stop the rest of the radiation. Mirrors could be added to the station to provide people artificially created day and night cycle.
O’Neill cylinder is an interesting proposal for a space habitat. It would offer a lot of space for people, but as with other proposed stations, building it would require an immense amount of resources. In the future, resources for building an O’Neill cylinder could be harvested from smaller planets or from the asteroid belt.
One suggestion is to build the habitats block by block, with smaller modules. Two modules could be interconnected with a long rope. By rotating the modules around the rope, artificial gravity could be created. This station could be expanded later, after the first inhabitants have already arrived. Modules could be light structures, that would be only filled at the space. This would make it possible to bring the modules from Earth.
The good side of the modular habitats is that it does not require massive initial investment to build. Habitat can be enlarged block by block, as required. Building a habitat like this would be possible with the current technology, and the resources could be brought from the Earth. However, large scale habitats are hard to build this way. Also, the space radiation could pose a problem, and radiation shielding would be expensive.
Resources already available in the solar system could be used in an ingenious way. Bubbleworld is an concept, where an interior of an asteroid is excavated, and a large habitat is built inside it. This would allow thousands of people to live there. Rotation of the asteroid would produce artificial gravity inside it. The soil of the asteroid would protect inhabitants from space radiation and resources could be harvested already in the building phase. We do not have technology to build bubbleworlds, yet.
In the future, space habitats could be built practically in every location of the Solar System. Interesting points near the Earth are Lagrange points between the Moon and the Earth, where the station would be in close proximity to Earth. Other interesting points are Lagrange points between the Sun and Mars and Venus. Asteroid belt might be an interesting location because of its resources.
When going farther the radiation energy from the Sun is not as intense, which would probably require using some other energy harvesting method than solar power. Solar power would probably be enough to keep the interior of the station warm enough, but electricity would have to be made with other methods. Electricity could be generated with fusion reactors, and the fuel for them could be harvested from the gas giants.
It is very possible that large-scale space habitats will be built in the future, maybe sooner we can imagine. The first stations will probably be quite small, but at some point, building large habitats will become possible. Space habitats could serve as a good waypoint before entering the surface of many inhospitable objects.