Those of a certain age and a certain bent can't fail to look at this beautiful depiction of the interior of a space station without a sense of nostalgia. Because, though Don Davis (in this case) depicts a presumably far-future vision of human space colonies, the art itself is very much of its time: the 1970s.
It's easy to mistake as being conceptual art for speculative fiction, but in fact this image, and the others here, come about as a result of successive summer studies from the collective brains of NASA, Princeton and Stanford. Here's some of what they came up with.
The Stanford torus
Proposed at the 1975 Summer Study at Stanford University, the Stanford torus is one take on the popular ring-shaped (or toroidal) space station, envisaged to permanently house up to 150,000-odd people in outer space.
Key to the concept is the rotation of the ring. Rotate at the correct speed (which depends on its size) and you'll have just the centrifugal force needed to simulate Earth's gravity, though only on the inside of the torus' outward-facing surface.
If this sounds fanciful, the study went so far as to propose that a torus could be built from moon-matter flung into space with an electromagnetic catapult. So perfectly feasible, in other words.
The cylinder space station
Cylindrical space stations like the Lewis One and the O'Neill colony also rely on the principle of generating simulated gravity via rotation.
On the plus side, you can make one a hell of lot smaller than you can a toroidal space station, but the concept is more complicated: the rotation makes it tough to keep its solar panels (which are separate from the rotating cylinder) angled toward the Sun.
The solution proposed by physicist Gerard K. O'Neill (or perhaps one of his students) is ingenious: place one cylinder inside another so any gyroscopic effects cancel.
If that isn't enough ingenuity for one space station, O'Neill and co also planned to simulate night and day with adjustable mirrors.
The Bernal sphere
A sphere, you say? Look carefully: the habitable part is towards the middle — and don't be fooled by the colorful reflection in the mirror.
At this point you've already spotted the theme: Again, being a round shape (the roundest, in fact), the station is able to rotate to simulate gravity, though the force would drop away the farther you go from the sphere's equator. Like a toroidal space station, then, this would achieve a valley-like habitable space.
Though a sphere may sound less efficient in terms of the amount of stuff you'd need to build it, the shape is optimal when it comes to "minor considerations" like atmospheric pressure and radiation-protection.
Though a feature of the 1970s studies, the Bernal sphere was original proposed in the 1920s by John Desmond Bernal.
Check out the gallery for more pictures.
Source: The NASA Commons on Flickr
Come on Elon, I know read this!
A Lunar-based solar-powered Maglev launching system would also be less costly for launching Lunar-sourced probes to other planets.
First, every one of these concepts is feasible from an engineering standpoint. Dr. O'Neil's original concept developed out of a class exercise requiring students to determine if such a structure could be built, using technology from the 1940's.
Second, the major proposal put forth by the L-5 Society was to finance such projects by using them for low-gravity manufacturing, and as workplaces to build orbital solar satellites. These satellites would be placed in geosynchronous orbit and transmit power via microwaves to receiving antennas on the ground. The intensity of the microwaves would be very low, and the land beneath could still be used for farming.
In 1975 the projected busbar cost of the power produced was about $0.12/kwh which was not competitive with conventional power--largely because most of the actual costs for nuclear and fossil-fueled electrical generation are not paid for by the producer or user, but are instead left for the government to clean up.
The major advantages of such power generation are: 1) Truly vast amounts of power can be generated. More power passes through the geosynchronous orbit than humans have used as a species--daily. It will continue for millions of years. 2) Waste heat from generation stays off-planet. A particular consideration given our current warming cycle. 3) Difficult targets for terrorist actions, it takes lots of resources to attack a target in a 22,000 mile high orbit. 4) Ease of redirecting power as needed to various areas, reducing the infrastructure costs for power distribution. 5) None of the noise, air pollution, radiation, fuel transport or waste issues associated with conventional or other alternative energy production.
As far as orbital habitats themselves...
Being outside of most of the Earth's gravity well, they are perfect based to explore the rest of the solar system. They are better than the Moon because even lunar gravity vastly increases the costs of landing and take off from the moon. This might be offset by the use of electromagnetic mass accelerators to launch from the Moon, and with modern computerization, such a device might be used for landing...but it is vastly more complicated than docking to an orbital habitat.
We would be far better served as a society by devoting time an effort to constructing such a place than by any attempt to put people on Mars. In fact, building an orbital habitat is the logical stepping stone to Mars, and the vast resources of our solar system.
Even a lunar base is best served by orbital power generation, because on any planetary or lunar surface, "the sun only shines part of the day."
In space, the sun always shines.
For those with a military bent, the first rule in strategy is "take the high ground."
A base in any Lagrange Orbit is 250,000 miles from any attacker.
In 1970, NASA predicted humans colonizing in space several centuries hence. By 1977 they moved that up to the end of this century.
We could do it today, using off the shelf technology.
Our history of geological and planetary science only goes back a couple hundred years, but in that time we have discovered that the Earth is far more changeable, changes far faster, and is at a substantial risk from impacts with objects in space, than we ever dreamed.
Humans, like most animals, tend to assume that things are as they are, have always been that way, and will remain. Our biology uses this to develop habit patterns which serve us in our known environment--our brains exist to deal with exceptions. Our minds rapidly integrate exceptions, and soon they are 'normal.'
But in the solar system, our entire Earth is such a small part, that the solar system could lose thousands of Earth masses, and the lack would be insignificant.
We are like ants, fighting over a crumb, on the floor of a warehouse filled with food.
The key to prosperity is energy, millions of times more energy than we use is readily available only 22,000 miles away.
With cheap energy comes the ability to create and recycle anything physically possible which we can imagine.
The most practical structure for a Dyson sphere would be a huge number of habitats, as with Ringworld, materials don't currently exist which would permit a solid structure.