A partially completed Dyson sphere around a star.
INTRODUCTION
A Dyson sphere is a hypothetical megastructure that encompasses a star and captures a large percentage of its power output. The concept is a thought experiment that attempts to imagine how a spacefaring civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet's resources alone.
The concept of a Dyson sphere was postulated by the physicist Freeman Dyson in 1959 in an article to the Journal Science entitled "Search for Artificial Stellar Sources of Infra-Red Radiation". It is said that he got the idea from a 1945 science fiction novel by Olaf Stapledon entitled "Stat Maker".
FREEMAN DYSON
Freeman Dyson (1923-2020) was a physicist and mathematician who made contributions to the fields of astrophysics, quantum field theory and engineering. His last position was as professor emeritus at the Institute for Advanced Study in Princeton.
One other space related idea he promulgated was the use of nuclear bombs for space propulsion. The bombs would be exploded behind a spacecraft with a very substantial shield between them that would not only protect the spacecraft but act to transfer the explosive energy into forward kinetic energy.
PRACTICALITIES
The outline of a Dyson sphere is shown in the diagram below.
If the sphere is to enclose the Earth then the radius will have to be greater than the orbital radius of the Earth (150 million km). Let us then use a value of r = 2 x 108. Various estimates of the thickness required for stability of the sphere range around 1 million km. So let us take dr = 106. We might also assume a density of 1500 kg/m3 assuming carbon nanotubes or similar, although it might be argued as to whether the solar system environment has enough carbon for such a project.
The total mass required is then:
It does then seem very problematic as to where the construction materials for our Dyson sphere are to come.
Australian Space Academy