Fast Facts: Unnamed Zond (3MV-1A No. 4A)

This planned Venus flyby was lost when it exploded shortly afer launch.

Nation Union of Soviet Socialist Repulics (USSR)
Objective(s) Venus Flyby
Spacecraft 3MV-1A (No. 4A, also No. 2)
Spacecraft Mass 1,764 Pounds (800 Kilograms)
Mission Design and Management (OKB-1)
Launch Vehicle Molniya + Blok L (8K78 no. G15000-26)
Launch Date and Time Feb. 19, 1964 / 05:47:40 UT
Launch Site NIIP-5 / Site 1/5
Scientific Instruments 1. Radiation Derector
2. Charged Particle Detector
3. Magnetometer
4. Piezoelectric Detector
5. LA-2 Atomic Hdrogen Detector
6. Kassiopeya Radio Telescope
7. RSK-2M Ultraviolet and Roentgen Solar Radiation Experiment
8. VIKT-2 Technology Experiment
9. Plasma Engines


This was the second Soviet "Object-Probe" whose goal was to test systems in interplanetary space in preparation for actual landings and flybys of Venus and Mars.

Unlike its predecessor (see Kosmos 21), it appears not to have carried a lander. Its mission was to test its propulsion, thermal, and communications systems during a four month flight in the direction of Venus to a distance of about 25 million miles (40 million kilometers).

In this event, the spacecraft failed to reach Earth orbit due to a malfunction in the launch vehicle’s third stage. Later investigation indicated that a liquid oxygen leak through an unpressurized valve (the B4311-O) seal froze propellant in the main pipeline while the rocket was still on the launch pad. As a result, the pipeline cracked, leading to an explosion in the third stage.


Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.

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