The cycle “Return to the Future” consisted of the novels “The Mystery of Zero” and “Don Quixotes of the Universe”. The novel “The Mystery of Zero” is dedicated to proving that stellar flight is possible at sublight speed, when the flow of time on a starship slows down according to Einstein’s theory, which follows introduce the concept of “mass ratio”. The second novel, “Don Quixotes of the Universe,” is about the stay of astronauts on a twin planet during the Middle Ages. The hypothetical novels of the oldest Soviet science fiction writer pose moral problems and suggest possible scientific solutions. Drawings by A.M. Eremina.