Places to start settling

It has been clear to me for quite some time that open space is a far better destination for human colonization than any other planets. The reason for this is that in open space it is relatively easy to generate artificial gravity through rotating space ships. On Mars, the most likely planet for settling, you are stuck with the low gravity.

It also is clear to me that the most important thing that needs to happen before permanent settlements in space appear is cheaper travel into orbit. All that effort going to exploring the outer planets, and science done on the space station is mostly meaningless. It is the people building new generations of space ships that matter.

It has also been clear that once we get our first self sufficient settlement in space, it will only be a couple generations until we inhabit the entire solar system in huge numbers. Exponential growth will spread us quickly through the inner solar system, and mining is likely to occur in the outer solar system once we use up the building material closer to the sun.

In space access to energy is virtually unlimited. Once constructed, solar cells can survive millions of years because of the lack of corrosion. Once pointed at the sun, they will never have to deal with cloudy days, or nights. Also radiation from nuclear reactors really isn't the threat that it is on earth. This is why space is such a good place to settle relative to the bottom of the ocean, or Antarctica. While easier to get to, and rich in building materials, those are both energy poor places, while space is rich in both energy and building materials. Having access to so much more energy than people on earth can easily construct solutions to the obvious disadvantages of space.

But once we can get into space cheaply enough, then what? where do we start and what do we do?

The first thought I had was to start on our moon. It has a whole lot of building material, that could be sent to space using an elevator for construction of other ships. This is quite feasible, but the gravity on the moon is just enough to be annoying, and not enough to be helpful. The escape velocity of 2.38km/s is still going to cause trouble. A settlement at a lighter body could ultimately beat it.

The next thing I thought was the asteroid belt. The total mass of the asteroid belt though is only 4% of that of the moon so as a mining destination it is not quite so rich. Still, billions of people could live in ships constructed from those asteroids. A third of that weight comes from one individual asteroid. Ceres. Now we are talking, the gravity is only 0.02g so things could easily be shipped off of it to build space ships. Its mass is 9.43 x 10^20kg. This is huge. For comparison the world only produces 1x10^12kg of steel in any year. While we probably would have too little of certain elements, and will need to mine other asteroids for them, it is safe to say we could support more people from the remains of Ceres than currently live on earth.

Another way to go would be the moons of mars Phobos and Diemos. These are actually a whole lot smaller than Ceres, 1x10^15-1x10^16kg. Escape velocity from the smaller one is only 11.3 meters /second. I can almost jump that fast! They have an advantage over Ceres too since they are somewhat closer. Here it really would be practical to put a rotating ship in orbit only a few thousand feet above the moon, then have miners spend days on the moon, before returning to the ship at night.