GTOC is an international global trajectory optimization competition. The 11th competition was held in 2021. The problem statement is formulated by the winners of the previous edition. The solution must be found in 4 weeks. There are no restrictions on the participation. The competition was devoted to constructing a part of Dyson's sphere 100 years after our days. It was necessary to place 12 stations in a circular orbit around the Sun. To build the stations, it was possible to use 83,453 asteroids moving on the given elliptical orbits. Participants were allowed to transfer the asteroids with a continuous low thrust. To be able to move an asteroid, it was necessary to install a special engine on it, using the asteroid's matter as fuel to create low thrust. To install such engines, it was necessary to use no more than 10 spacecrafts, launched from Earth and controlled by impulses. Participants maximized the minimum weight of the stations among those built. The article describes the format of the competition, gives the problem statement, a summary of the results and the approaches used.