In 1979, Cosmos 1129 flew five female and two male rats for 18.5 days and allowed them to mate; no normal pregnancies resulted in flight, while a later ground study produced healthy litters

Cosmos 1129, a Soviet biosatellite, conducted groundbreaking research on rat reproduction in space. Through ground simulations that mimicked the stresses of launch and re-entry, the study discovered that the timing of events, along with stress, played a crucial role in delaying pregnancies. The research underscored the significant influence of confinement, disrupted schedules, and environmental factors on the reproductive success of the laboratory rats.