Names Soyuz 7K-L1 s/n 6 COSPAR ID 1968-013A Launch date 2 March 1968 Bus Soyuz 7K-L1 Decay date 7 March 1968 | Operator OKB-1 SATCAT no. 03134 Launch site Baikonur Cosmodrome Regime Low Earth orbit | |
 | ||
Mission type Lunar flyby
Spacecraft test Launch mass 5,140 kilograms (11,330 lb) Manufacturer S. P. Korolev Rocket and Space Corporation Energia Similar Zond 7, Zond 5, Soyuz 7K‑L1 No4L, Zond 8, Soyuz 7K‑L1 | ||
Zond 4, part of the Soviet Zond program and an unmanned version of Soyuz 7K-L1 manned Moon-flyby spacecraft, was one of the first Soviet experiments towards manned circumlunar spaceflight. It was launched to test the spaceworthiness of the new capsule and to gather data about flights in circumterrestrial space. It was the first Soviet spacecraft to possess a computer, the 34 kg Argon 11.
The spacecraft was successfully launched into a 354,000 km apogee orbit 180 degrees away from the Moon, It was launched away from the Moon probably to avoid trajectory complications with lunar gravity. However on re-entry the L1's guidance system failed. It hit the atmosphere precisely at the calculated time, but was not guided to generate lift and fly out of the atmosphere again. A ballistic re-entry would mean no recovery on Soviet soil, so the APO destruct system automatically blew up the capsule at 10 to 15 km altitude, 180–200 km off the African coast at Guinea.