Mars 1 / 2MV-4 Credit - NASA

Mass: 6,490 kg (14,300 lb).

• 1961 January 18 - Venera preparations - Launch Vehicle: Soyuz.
  The VVS contingent arrives at Tyuratam at 23:45 aboard an Il-14 for the Venera launch. Chertok is in charge of launch preparations. Due to various radio system problems, there can be no launch until 26 January. The death of Nedelin and the others still hangs over the cosmodrome.

• 1961 January 20 - Venera preparations - Launch Vehicle: R-9, Soyuz.
  Korolev plans three launches between 20 January and 14 February, but clearly his teams are not ready to accomplish this. There was insufficient testing of the Object V Venera spacecraft before it was shipped from OKB-1 to the cosmodrome. OKB-1 is trying to finish Object V on site, at the same time preparing the next Vostok 3KA and an R-9 ICBM for launch. Object V is not ready, the ability of its systems to function at long ranges and periods of time on the voyage to Venus are suspect. In Kamanin's opinion, it is diverting the crews from the higher priority manned and military projects.

• 1961 January 26 - Venera delays - Launch Vehicle: R-16, Soyuz.
  The Object V launch is delayed to 1 February. Yangel has also had to postpone the next R-16 launch attempt to 26-30 January.

• 1961 January 31 - Back at Tyuratam - Launch Vehicle: R-16, Soyuz.
  Kamanin flies to the cosmodrome with Korolev, Keldysh, Moskalenko, General Semenov, and others. Yangel's R-16 ICBM is not ready for launch yet due to continuing problems with the radio systems. The Venera is set for a 2 February launch attempt.

• 1961 February 1 - Venera rolled out to pad - Launch Vehicle: Soyuz.
  The booster is 5 to 7 m taller than the Vostok. One gyroscope has to be replaced on the pad. Fuelling begins at 23:30. At 02:00 the launch is scrubbed due to continuing gyro problems. Next attempt is set for 4 February.

• 1962 September 12 - Sputnik 21 - Program: Venera. Launch Site: Baikonur. Launch Complex: LC1. Launch Vehicle: Soyuz. FAILURE: At T+531 sec, the fourth vernier chamber of Stage 3's 8D715K engine exploded because the LOX cut-off valve had not closed as scheduled and LOX flowed into the hot chamber. Mass: 6,500 kg (14,300 lb). Perigee: 179 km (111 mi). Apogee: 218 km (135 mi). Inclination: 64.90 deg. Period: 88.40 min.
  The escape stage entered parking orbit but the main engine cut off just 0.8 s after ignition due to cavitation in the oxidiser pump and pump failure.