Three teenagers — Sveta Ishenova from
Bukhara, Sasha Ivanenko from
Donetsk and
Muscovite Fedya Druzhinin — win the All-Union Children's Space Competition and after completing the special training course, go to the first ever children's flight on the Astra spacecraft. During the flight the only adult on the ship, Captain Egor Kalinovsky, gets sick and is placed in the isolation ward. A series of short-term emergencies that arise shortly after this force the child astronauts to make independent decisions in conditions when erroneous actions threaten to destroy the crew and the ship. With the honor of withstanding all the tests, the film's characters suddenly discover that the Astra is an underground simulator, and the expedition of the "first three", which has never really left Earth, is a psychological experiment designed to find out the prospects of a real children's space flight. At the same time it turns out that Fedya, who accidentally learned about the real mission of the Astra shortly before the start, hid it from Sveta and Sasha, with the objective of preventing failure of the important experiment. Despite the fact that the "big space travel" turns out to be just a training session, all three of its participants, who at the given time find a way out of the simulator and get to the surface at the main entrance to the Flight Control Center, are met as real space heroes. ==Cast==