Cosmos 154

Cosmos 154 was a Soviet test satellite precursor to the Zond series. The spacecraft was designed to launch a crew from the Earth to conduct a flyby and return to Earth. The Cosmos 146 and 154 flights have been regarded as tests of the Zond complex involving the firing of the fourth stage of the Proton K/Block D rocket to put the L1 spacecraft into an elliptical trajectory to test high speed re-entry. L1 was a Soviet spacecraft launched on Proton, designed in parallel of 7K-L1, which flew on the N-1 launcher. It was conceived to carry out crewed flybys of the Moon, like Apollo 8. This spacecraft sent the first living beings to fly over the Moon, turtles, on board Zond 5. The work made on this spacecraft will be used for the improvement of the Soyuz spacecraft.