There was some very famous sci-fi that came out of the Eastern Bloc. Many people have heard of Stalker (1979) by Andrei Tarkovsky. I think a lot of people associate Stalker with the video game series that has been around the last few (or more?) years, but the film is a sci-fi classic. Solaris is a famous sci-fi novel from Stanislaw Lem, a Pole, that was made into a film (also by Tarkovsky).

The space race also inspired a lot of enthusiasm for space and what was essentially science fiction. You can find images in the Soviet equivalent of something like popular science that will seem very familiar to you if you are familiar with the same era (1950s) imagery in the West. See examples here.