On March 9, 1961, Chernushka the Soviet Space Dog boldly ventured into the final frontier with her crew of mice, guinea pigs, and a dummy cosmonaut named Ivan Ivanovich. No, that’s not the setup to some kids’ cartoon—it’s the story of one of the most famous cosmonauts of the Soviet space program.

In the early days of spaceflight, nobody knew if it could be made safe for people. The Soviets decided to find out by sending dogs into space before they sent people. These intrepid canines were called the Soviet Space Dogs. Chernushka was an interesting case: she was actually a second-generation canine cosmonaut. Her mother, Pushinka, had gone up on an earlier space flight and was given to the U.S. President’s daughter as a gift. She had a litter of puppies, dubbed the “Pupniks,” and one of them was chosen to follow in her mother’s footsteps as the Space Dog for the Sputnik 9 mission.

And what an important mission it was. It was the first spaceship equipped with an ejection system, and that’s what Ivan Ivanovich was there to test. On the journey back to Earth, Ivan was successfully ejected, and Chernushka and her crew survived the trip. This was one of the trips that proved to the Soviet scientists that they could take the risk of sending a human pilot, which they did soon after. Chernushka was hailed as a national hero. The mice and guinea pigs, not so much.