A sunken Dyson Sphere was a Dyson Sphere that was solid all the way to a star's core. Construction was difficult because it required going into deep a star without vaporizing to death.
(Note: The background section of this page uses most of the same words as Terra Futura's page on Solid Dyson Spheres to save time.)
The photovoltaic effect was discovered in 1839 by French physicist, Alexandre-Edmond Becquerel, the father of the guy who discovered radioactivity. This was followed in 1887 by the discovery of the photoelectric effect by Heinrich Hertz, an ethnically half-Jewish, half-German Lutheran physicist. Then, in 1905, Jewish physicist Albert Einstein discovered that light was made of particles called photons. The first semiconductor solar cell was produced in 1946 by Russell Ohl who would become one of the inventors of the transistor. The first practical photovoltaic cells were created by Bell Labs in 1954. In 1958, solar cells started being used on spacecraft. Soon, solar cells would become cheaper.
In the late 1960s, a scientist named Elliot Berman invented a new process for producing silicon solar panels in a ribbon. He started working at Exxon to make improvements. By the end of the 20th century, solar panels were commonplace. It was now possible to incorporate them into roofs of houses. Polycrystalline silicon was by now the most common material for solar panels. There was one problem. Polycrystalline silicon had to be pure. This made them expensive. During the second decade of the 21st century, they were replaced with thin-film solar panels which could disappear into windows, cell phones, television, etc. This made solar power commonplace. This was important as Masdar City would soon be finished.
The first phase of the Masdar City project was completed in 2015. This was the world's first carbon-neutral, zero-waste, and fully sustainable city. It ran on a multitude of clean energies. These included the largest solar power plant in the Middle East, rooftop photovoltaics, wind farms, a geothermal power plant, and a hydrogen power plant. A desalination plant provided water for the city. There were also extensive recycling systems. These were solar-powered. Automobiles were not allowed. Instead, mass transit and personal rapid transit dominated the roads. It had a university, an institute of science and technology, and was the headquarters of the International Renewable Energy Agency. Vertical farms provided food the people that lived there. By 2025, Masdar City was completed. As the 21st century continued, cities like Masdar City dominated the Middle East. Even a reconstruction of Jerusalem by the nations of Israel and Palestine, which were in a personal union to maintain stability, complete with a new Holy Temple was just like Masdar City. As solar power started coming from space, these cities would adapt.
Solar power satellites were first proposed as a concept in the 1970s. There was one problem. Solar power satellites required a lot of material to be built. Advances in nanotechnology and transmission efficiency allowed the solar power satellite to become commercially viable in the 2040s. In space, collection of solar power was free from atmospheric gases, weather, and wildlife interference because the solar energy was sent to Earth by way of electromagnetic waves. It also worked 24 hour a day and was redirectable. It could even be used as a weapon which was one of the uses during World War III. Though vulnerable to solar radiation at first, by the end of World War III, advanced shielding made them useful as a power source. This became a highly successful industry. Along with other non-polluting resources, solar power satellites unseated the dominance of petroleum. This eventually led to the construction of a Dyson Swarm.
The Dyson Swarm was the concept proposed by Freeman Dyson in 1959. The concept was a swarm of solar power satellites and, sometimes, space colonies that surrounded a star. As the human race added more solar power satellites to collect solar energy, a scientist from Jerusalem, Yaron Ben-Avraham, proposed to the Earth Federation government which was headquartered there that they use what they have built so far to create a Dyson Swarm. The government approved. But they also had to get the approval of the Galactic Alliance. They did. The Dyson Swarm was completed in 2995. Other Dyson Swarms followed. The advantage of a Dyson Swarm was that it allowed light and heat to pass through keeping Earth and other planets illuminated. The thickness of the Dyson Swarm depended on the architecture and components. This was not a problem. As time went on this led to a type of Dyson Sphere called a Dyson Shell.
A Dyson Shell was the most common type of Dyson Sphere in science fiction. It was through advances in materials that this became possible. Using artificial gravity, humans could survive in Earth-like conditions. A star's gravity could not anchor a Dyson Shell. Gravitic propulsion systems solved that problem. A way had been found to create a day-night cycle. Force fields protected the Dyson Shell from impacts with outside rocks. Near-100% efficient recycling systems were also incorporated. There was just one problem. It was controversial. To build a Dyson Shell, you had to disassemble an entire solar system. In response, the Galactic Alliance passed a law that banned construction in a star system containing life. This meant that Dyson Shells were not as common as Dyson Swarms. The Dyson Shells that were built were successful. Some of them even became mobile. Years later, all Dyson Shells would be converted into solid Dyson Spheres.
Hundreds of thousands of years into the future, Dyson Shells had been in every uninhabited star system in more than one galaxy. But by this time, work began to convert them into solid Dyson Spheres which were solid all the way to the star's surface. There was a problem. I required the destruction of dozens of star systems even with replicators. They used the planets of a galaxy with no life in it what so ever to do it as well as other uninhabited star systems. Once finished, these solid Dyson Spheres could quadrillion inhabitants. These solid Dyson Spheres were mobile than Dyson Shells because they were more stable. As advances in materials arrived, Dyson Spheres would go even deeper. These were sunken Dyson Spheres.
Tech Level: 15
A sunken Dyson Sphere would require advanced materials. Millions of years into the future, the technology was there. Materials were advanced enough to resist the heat of a star. Combined with advanced force fields which acted like a cage, this design was workable. The force fields could not completely block the flow of hydrogen fuel and fusion byproducts or the Dyson Sphere would explode. So like with force fields on starships, the open framework was there to allow it to pass. The far greater energy density at the core meant that a sunken Dyson Sphere could have even more power. Robots that could withstand the high temperatures did most of the work. This was one of the big energy producers of the universe.