Zond program

Two tortoises and other lifeforms aboard Zond 5 were the first terrestrial organisms to travel around the Moon and return to Earth.

After two failures, Zond 3 was sent on a test mission, becoming the second spacecraft to photograph the far side of the Moon (after Luna 3).

The Soyuz 7K-L1 (also mentioned just as L1) spacecraft was used for the Moon-aimed missions, stripped down to make it possible to launch around the Moon from the Earth.

They were launched on the Proton rocket which was just powerful enough to send the Zond on a free return trajectory around the Moon without going into lunar orbit (the same kind of path flown by Apollo 13 in its emergency abort).

In the beginning, there were serious reliability problems with both the new Proton rocket and the similarly new Soyuz spacecraft, but the test flights pressed ahead with some glitches.