Although from a scientific point of view, all this is completely justified, but from the ground you somehow treat the propellers in the form of a solar sail as some kind of child's play. Where is he good for? Where can you fly on it?
However, this topic has been developed for a long time and seriously …
The Znamya space projects program is a series of experiments on working with space mirrors, that is, special reflectors that reflect sunlight and illuminate the earth's surface. Banner 2 project - solar sail 20 meters wide. It was launched aboard Progress from the Baikonur cosmodrome on October 27, 1992. When visiting the Mir station, its crew installed a reflector deployment unit on board Progress. After undocking and maneuvers, the Progress spacecraft successfully deployed the reflector.
Design: Eight coils with stripes of reflective polyethylene terephthalate film with a thickness of only 5 microns were installed on board the Progress M-15 cargo spacecraft. This film is widely used today almost everywhere: from packaging products to creating metallized solar sails. In orbit, the spacecraft would begin to rotate, and the coils would gradually unwind the film. Under the action of centrifugal force, the mirror unfolded, and a special flexible ring ensured the round shape of the mirror.
On February 4, 1993, the Znamya-2 experiment was successfully carried out. A 20-meter mirror made of the thinnest aluminized film unfolded in the normal mode and illuminated the Earth. Since Progress M-15 was rushing in orbit at a tremendous speed, a “sunbeam” about 5 km in diameter swept across the Earth's surface just as quickly - at a speed of 8 km / s. Therefore, the inhabitants of Europe did not observe the "magic sunrise" in the middle of the night - only a bright flash in the sky. A spot of light from "Znamya-2" ran from France to Belarus, where it was caught by the sunrise. Despite the fact that over Europe was overcast, many people saw a flash of light. German meteorologists even recorded the illumination from the light spot "Znamya-2", it was approximately 1 lux (1 lumen per square meter). For comparison, a 60-watt incandescent light bulb has a brightness of 700-800 lumens. At first glance, the cosmic mirror shone completely dim, but it should be remembered that it did not have such a large reflective surface area, and, moreover, it did not illuminate a room of 10 square meters. m, and a circle with a diameter of 5000 m. In general, scientists compared the light from the "Banner-2" with the light of the full moon, which is very good for a 20-m mirror.
The Banner 2.5 project was head and shoulders above its predecessor. The mirror should have been perceived from Earth as 5-10 full moons in brightness and formed a trail about 7 km in diameter, which could be controlled by holding it in one place for a long time.
In "Znamya-2.5" the same technologies were used as in the first experiment, only the mirror was 5 m larger - 25 m in diameter. It should have produced a light spot about 8 km in size. On February 4, 1999, the mirror installed on board the Progress M40 transport spacecraft began to unfold, but it caught on the antenna and got entangled in it. The experiment failed and the ship was sunk in the ocean.
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The solar mirror is a slightly concave shell with a diameter of 25 m, made of a thin film with a mirror surface, which is attached around the perimeter of the station. The shell is opened and held in the open position by centrifugal forces. However, the project failed. At the beginning of the deployment, the shell caught on the antenna.
The third project, Znamya-3, never materialized.
Mankind is already capable of assembling a mirror in space, which will shine dozens of times brighter than the full moon. The benefits are obvious: the "free" energy of the Sun is used for lighting; you can immediately illuminate a large region or city; increase the energy efficiency of ground-based solar power plants by several times; the space lighting system is not afraid of any terrestrial cataclysms like earthquakes and hurricanes. Also, such a mirror could extend the growing season of useful plants.
Difficulties in the implementation of large projects of space mirrors still lie only in the imperfection of technologies for launching cargo into space. In a geostationary orbit (optimal for a mirror), a huge space mirror must be constructed. In turn, in lower circular orbits, for continuous illumination of a section of the Earth, it will be necessary to use many separate mirrors, which also does not reduce the cost of the project and, moreover, runs into the problem of space debris. But, one way or another, humanity has an interesting opportunity to increase the comfort of its habitation not within the framework of a single room, but in a large city or an entire region. In the near future, it is possible that new technologies for delivering cargo into space will appear, technologies for manufacturing space mirrors using, for example, nanoparticles based on metamaterials, will be created. And then,finally, humanity will be able to realize an old dream and create its own artificial sun in the night sky.