The unmanned Vostok test flight carried a dog, mice, and a guinea pig, alongside a mannequin dubbed Ivan Ivanovich that was ejected and parachuted to Earth to test the cosmonaut escape system. Its success, following the earlier failures, gave Soviet engineers confidence to schedule Yuri Gagarin's historic flight just five weeks later.
Inside the Vostok capsule sat a stuffed dummy nicknamed Ivan Ivanovich, dressed in a full cosmonaut suit, with a tape recorder in his chest playing recordings of a choir and a recipe for cabbage soup so that any radio eavesdroppers would not mistake the transmission for a real human voice.
The dog Chernushka orbited the Earth once before the descent module fired its engines and Ivan Ivanovich was ejected and parachuted separately from the capsule, exactly as a human cosmonaut would need to do in an emergency. Soviet recovery teams found both safely.
The flight resolved lingering doubts among Korolev's engineers about the ejection seat and the automatic reentry sequence. One more test flight, Zvezdochka's on March 25, would follow before Yuri Gagarin's Vostok 1 launched on April 12, 1961, becoming the first human in space.