A modified version of the first Soyuz spacecraft was designed for manned circumlunar flight. None of the Zond ("probe") missions were ever actually manned, although early plans did call for Zond 7 to have a crew. Ultimately, 3 manned circumlunar missions were to have occurred.
Zond 1, 2, & 3 were versions of unmanned probes to Venus and had nothing to do with the circumlunar Zond.
L1 (Zond) circumlunar spacecraft (NASA)
Cosmos 146, 10-18 March 1967. First flight test of the Soyuz based L1 craft. Purpose of the flight was a test of the Block D fourth state of the Proton launch vehicle.
Cosmos 154, 8-10 April 1967. This was to test the reentry characteristics of the L1, but Block D did not fire and the test could not be completed.
28 September 1967. Launch failure due to one of the Proton engines failing to fire. The emergency escape system pulled the descent module free of the rocket.
22 November 1967. Launch failure due to a second stage engine failure. The emergency escape system pulled the descent module free but the landing rockets fired prematurely during the parachute descent.
Zond 4, 2-9 March 1968, was launched into a high (330,000 km apogee) orbit 180 degrees away from the moon. The guidance system failed and self-destruct was initiated.
23 April 1968. Launch failure, the escape system fired by mistake during second stage operation.
Zond 5, 14-21 September 1968, did fly a successful circumlunar mission. Upon reentry, the gyroscope was disabled and the capsule came in at 20G's. It was recovered.
Zond 6, 10-17 November 1968, in November of 1968 also completed a circumlunar mission. Gasket failure caused a depressurization of the (unoccupied) crew compartment.
20 January 1969. Launch failure. The second and third stages of the Proton launch vehicle performed so poorly the vehicle had to be destroyed.
20 February 1969. Launch failure. First N-1 rocket flight test carried a simplified L1. A failure in the engine control system resulted in a spectacular explosion. The L1 was ejected and descended safely.
3 July 1969. Another mishap and explosion of the N-1 rocket and destruction of the launch tower. The L1 module again was ejected and descended safely.
Zond 7, 7-14 August 1969, was originally scheduled for early December of 1968. A decision on whether or not to man this mission was to have been made around December 1. Technical difficulties delayed the flight into January. By that time, the United States had already flown Apollo 8 around the moon. The Soviets decided not to fly any of the manned circumlunar flights. Zond 7 finally did fly, unmanned, in August of 1969. It was the only Zond flight which could have gotten a crew back to Earth unharmed.
Zond 8, 20-27 October 1970, was flown as a purely research circumlunar mission. As had happened before, the guidance system failed and reentry was at 20G's.
|Proton configured for L1 (Zond). Note the modified
Soyuz shroud at the top.
Here is additional information on the Soviet lunar program L2 Lunar Orbit Module and the L3 Lunar Lander.