Zond was the name given to two distinct series of Sovietrobotic spacecraft launched between 1964 and 1970. The first series, based on the 3MV planetary probe, was intended to gather information about nearby planets. The second series of test spacecraft was intended as a precursor to crewed circumlunar loop flights, using a stripped-down variant of Soyuz spacecraft, consisting of the service and descent modules, but lacking the orbital module. Two tortoises and other lifeforms aboard Zond 5 were the first terrestrial organisms to travel around the Moon and return to Earth.
Missions based on the 3MV planetary probe
The first three missions were based on the model 3MV planetary probe, intended to explore Venus and Mars. After two failures, Zond 3 was sent on a test mission, becoming the second spacecraft to photograph the far side of the Moon. It then continued out to the orbit of Mars in order to test telemetry and spacecraft systems.
Circumlunar missions
The missions Zond 4 through Zond 8 were test flights for the Soviet Moonshot during the Moon race. The Soyuz 7K-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. With minor modification, Zond was capable of carrying two cosmonauts. 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. The majority of test flights from 1967–1970 showed problems during re-entry. The Zond spacecraft made only uncrewed automatic flights. Four of these suffered malfunctions that would have injured or killed any crew. Instrumentation flown on these missions gathered data on micrometeor flux, solar and cosmic rays, magnetic fields, radio emissions, and solar wind. Many photographs were taken and biological payloads were also flown.
* Second stage failure. The Zond capsule was safely recovered. The rocket crashed 300 km downrange.
* Attempted Lunar flyby
Zond 4
* Launched 2 March 1968
* Study of remote regions of circumterrestrial space, development of new on-board systems and units of space stations.
* Returned to Earth 7 March 1968 — Self destruct system automatically blew up the capsule at 10 to 15 km altitude, 180–200 km off the African coast at Guinea.
* Block D stage exploded on the pad, killing three people.
Zond 5
* Launched 15 September 1968
* Circumlunar 18 September 1968
* Returned to Earth 21 September 1968
* A biological payload of two Russian tortoises, wine flies, meal worms, plants, seeds, bacteria, and other living matter was included in the flight and were the first Earth lifeforms to travel around the Moon and return safely.
* The first spacecraft to circle the Moon and return to land on Earth.
