Some artificial megastructures to colonize the galaxy
The ISS, the international space station, is not only scientifically important, it is also the result of the collaboration of several countries on all continents. This football-sized laboratory is one of the costliest projects in history – approximately $ 115 billion since its inception. Its size, its cost can give an idea of what is called a “megastructure”. Yet, this is only the beginning.
Humanity has been around for a few million years, but has only been collaborating on a global project beyond Earth, in space, for about thirty years.
If our civilization hopes to rise, it will have to ignite a cosmic vision: to go and see other stars, other star systems, or even expect to have to live in autonomous stations on the move.
Science fiction has no shortage of ideas to represent this future: between “death stars”, giant spaceships, or stellar engines, we find everything. These giant structures, sometimes the size of a planet, are called “megastructures”.
Many cosmologists, in addition to science fiction writers, have already addressed the question.
It goes without saying that to create artificial mega-infrastructures in the galaxy, it takes a considerable amount of energy and resources. So for each megastructure that I present in this article, I put in the type of civilization it takes to be to hope to make such things. Recall that the Kardashev scale is logarithmic and currently we would be Type 0.7 (the scale is logarithmic, so we would use about 0.1% of our planet’s energy).
The Stanford torus
In the genre of structures capable of producing artificial gravity, the circular and rotating space station is a very good candidate.
The Stanford torus (the “torus” is the geometric shape of the donut) takes up this idea of a rotating vessel, but on a much larger scale. The original idea indeed includes a hollow torus 1.8 km in diameter, rotating at 1 revolution per minute and permanently housing around 10,000 people.
The idea was first proposed in 1975 at Stanford University, hence the name. Its dimensions are adapted so that a rotation of 1 revolution per minute simulates a force of gravity of 1 g.
This megastructure is not very impressive (compared to the other structures I am talking about in this article): indeed, humanity could build one. You have the technology, and all you need is the will and the money.
This megastructure needs to be a Type 1 – civilization: you don’t need a lot of resources, you just need a lot of raw material, which can be found in asteroids or even on Earth.
The O’Neill cylinder
The Stanford torus only produces artificial gravity on the outer edge of the inner wall of the torus. Everything else is therefore a bit of “wasted” space to put people or infrastructure in.
Conversely, the O’Neill cylinder is a tube that turns as if it were rolling: the sensation of artificial gravity is therefore obtained over the entire internal wall of the cylinder, which multiplies the living area. The exterior of the cylinder could for example be covered with solar panels.
The original idea, proposed by Gerard O’Neill in 1976, was to put two cylinders end to end, rotating in opposite directions to each other: each cylinder compensates for the angular momentum of the other. This makes it easier to control the rotation: each cylinder then being the fulcrum for the other.
The typical cylinder is three kilometers in radius and 30 kilometers in length! So it’s much bigger than the Stanford Torus. So, if the Stanford torus is a vessel idea, the much larger O’Neill cylinder may begin to serve as a colony.
Dyson’s sphere / bubble / swarm
A Dyson sphere (named after an idea by Freeman Dyson in the 1960s) is a shell completely covering a star and intended to capture all of its radiation (heat, light, etc.) in order to produce usable energy :
In practice, it would be unthinkable to cover the star on its surface: it is far too hot there. Fortunately, in the case of a complete sphere, the total energy captured remains the same no matter how far away you are.
The problem is just that the further away we go, the larger the surface of the sphere, and therefore the more raw material is needed. It is estimated that if one places oneself at the level of the Earth’s orbit, then the necessary mass would correspond to that of Jupiter.
We will say that raw material is not a problem when we are a Type 2 civilization, but it would still amount to a lot of matter, especially since gas giants like Jupiter are made up of … gas, not gas. rock or metals, although it is highly likely that a Type 2 could fuse hydrogen as it pleases to produce any element on the periodic table at its convenience.
Often, instead of a complete Dyson sphere, it is proposed to place a constellation of giant solar panels around the Sun. By using a multitude of solar panels and placing them all around the star, we get what is called a Dyson swarm.
There is no need here to cover the entire star: the amount of raw material needed is therefore much lower: the mass of the planet Mercury could be more than enough here.
A matryoshka brain
The purpose of a Dyson swarm is to use the star as a source of energy for a civilization.
If such a megastructure is used in particular to power a giant computer, then it is called a matryoshka brain. If the word “brain” refers to the artificial intelligence and the computational capacity of such a construction, the qualifier “matryoshka” rather refers to the layered structure of this construction, like Russian dolls (matryoshka) .
The idea is to place energy sensors all around the star, but also in the form of nested layers. The reason for this is that the inner layers near the star will be very hot and radiate energy outward in the form of heat. The outer layers capture this energy and use it in turn. Each layer therefore receives energy, uses part of it to calculate and rejects the rest (by losses). An N + 1 layer is therefore supplied by the losses of the N layer.
The goal is of course to have the most efficient system possible, to maximize the efficiency of the star’s energy to produce calculations. Ideally, all of the energy would be captured and transformed into computing power .