OKB-1 Chief Designer Sergei Korolev switched over the role of Space Probe design and construction to aviation manufacturer NPO Lavochkin. Many changes were made to the 3MV, which began receiving the new designation system used by Lavochkin, the first one being V-67 (Venus 1967). This included the removal of the Radiator spheres on the ends of the solar panels, replaced by the use antennas as a radiator, increasing the size of the panels. The probe was also heavier than the previous Venera 3. This was due to the change in Soviet thinking of the possible temperature of Venus, with this leading to the V-67 lander being strengthened (although still not strong enough) for the expected harsher environment. It was also equipped with an ablative heat shield.* After Venera 4's failure to reach the surface of Venus intact, the next 3MV probes (Venera 5 and 6) were strengthened again, this time to withstand a 450-g (compared to the 300-g entry of Venera 4) reentry due to the 1969 launch window's higher velocity. The V-70 design took this further, with the capsule being slightly more egg-shaped. It was designed to survive 150 atmospheres and 540°C (1004°F). The Parachute was also changed to the heavier weight and the lander was set to -8°C before detaching from the 3MV bus. Due to these changes, Venera-7 became the first spacecraft to land on Venus, and another planet successfully. The final version of the 3MV bus, the V-72 probes; were launched in early 1972, with one failing to reach Venus (Kosmos 482 which was still orbiting earth as of 2011). The 3MV was superseded by the newer 4V-1 probes beginning in 1975 with Venera 9 and 10, based on the M-71/73 probes (Mars-2-7). Variants Venera 3MV-1A: Kosmos 21 (3MV-1 No.1), 3MV-1A (failure) Venera 3MV-1: Zond 3MV-1 No.2 (failure), Kosmos 27 (3MV-1 No.3), Zond 1 (3MV-1 No.4)) Mars 3MV-4A: Zond 2 (3MV-4A No.2), Zond 3 (3MV-4A No.3) Venera 3MV-4: Venera 2 (3MV-4 No.4), Kosmos 96 (3MV-4 No.6) Venera 3MV-3: Venera 3 (3MV-3 No.1), Venera 3MV-3 Venera 3V (V-67): Venera 4 (V-67 No. 310), Kosmos 159 (V-67 No.311) Venera 3V (V-69) Venera 5 (V-69 No. 330), Venera 6 (V-69 No. 331) Venera 3V (V-70): Venera 7 (V-70 No.630), Kosmos 359 (V-70 No.631) Venera 3V (V-72): Venera 8 (V-72 No.670), Kosmos 482 (V-72 No.671) See also Soviet space program Zond program Venera 2MV 4MV References "The Mystery of Zond