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Missions to Venus

Venera-72 (Kosmos-482)

Zond-2: An early attempt to touch Mars?

50 years ago, on Nov. 30, 1964, the USSR announced the launch of the Zond-2 spacecraft toward Mars, which would chase a pair of NASA's Mariner probes heading to the Red Planet for the first time. Unfortunately, it failed soon after liftoff and most details on the mission remained secret for decades. Only in 2011, did new documents reveal that for decades the assumptions about the goals of the Zond-2 mission on Mars had probably been wrong, requiring a re-write of the Mars exploration history!

Previous chapter: Zond-1 mission

Mars

Above: One of the best images of Mars preceding the beginning of the Space Era was taken on Aug. 24, 1956, with a 60-inch reflecting telescope at Mt. Wilson, California.

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Zond-2 mission

Preparations for what would become the Zond-2 mission started right after the Venus launch campaign in the Spring of 1964. This time, engineers at Sergei Korolev's OKB-1 had to rush to catch the only window available for launches to Mars in the following two years. As it became publicly known only decades later, back in 1963, plans were made to send four 3MV vehicles toward the Red Planet, two of which, designated 3MV-3, would attempt to deliver landers on the surface of Mars for the first time! The two other probes -- 3MV-4 -- would fly by the mysterious planet and take close-up photos of its surface.

The most challenging part of the mission was obviously the development of a landing system, which had the task of gradually reducing the descent velocity of the lander so it could reach the surface intact. Engineers had to rely on scarce data about the Martian atmosphere obtained from ground-based observations, when designing their spacecraft and its descent sequence.

By the end of November 1964, Korolev and his superiors in the industry wrote to the Central Committee of the Communist Party that the latest observations of Mars made during 1963 and the beginning of 1964 with the use of spectrographic methods had revealed that the density of the Martian atmosphere was three or even four times lower than previously expected. It required a drastic re-design of the landing missions. The flyby probes also had to be modified. This effort faced considerable technical challenges, at a time when the OKB-1 design bureau and its contractors had to focus their maximum effort on preparations for the launch of the first multi-member crew onboard the Voskhod spacecraft. As a result, it would be impossible to meet the November 1964 launch window, the letter said.

Instead, the officials proposed a considerably streamlined launch manifest:

November - beginning of December: The launch of the single spacecraft which was in high degree of readiness toward Mars. The probe would be used for flight testing all the systems onboard MV-type vehicles and for some scientific experiments. If the spacecraft functioned as expected, ground control would attempt to conduct a course-correction to guide it right into Mars (essentially for destructive entry into its atmosphere) with the delivery of a pennant onto the planet, Korolev wrote.
The remaining three spacecraft of the MV fleet would be re-tested on the ground and one or two of these vehicles would be launched in the first half of 1965 on another test mission under the name "Zond," followed by the remaining vehicle in November 1965 toward Venus. (509)

Unlike its predecessor Mars-1, Zond-2 would not include 8-centimeter and 1-meter wavelength transmitters. However it sported six experimental plasma thrusters, which could be fired on commands from Earth to control the probe's attitude, saving the propellant of a regular gas-powered attitude control system. (633)

The launch

The 3MV-4 No. 2 spacecraft (a.k.a. 3MV-4A) lifted off from Site 1 in Tyuratam on a Molniya rocket on Nov. 30. 1964. (52) After dropping its third stage in a parking orbit around the Earth, the spacecraft was successfully inserted into a trajectory toward Mars. However the rush development of the spacecraft led to the failure of its solar panels to deploy and problems with the power supply system. According to various reports, the solar panels either completely stuck or did not fully open. In addition, radiators of the thermal control system (mounted on the same deployable structure with the solar panels) were also affected and a programming timer, PVU, had problems as well. (202) After a series of maneuvers, the probe finally deployed its panels on Dec. 15, 1964, more than two weeks after the liftoff. (84)

Ground controllers were able for the first time to test communications via a narrow-angle antenna and fire plasma engines, before communications broke down a month after the launch.

Obviously, none of this information was publicly released at the time. Western observers concluded that the Zond-2 mission had likely been intended to fly by Mars but that it had apparently stopped communicating with ground control in April 1965. On August 6, 1965, the dead spacecraft passed as close as 1,500 kilometers from the Red Planet. (185)

Until the publication of the November 1964 letter in 2011, most Western sources and a number of the post-Soviet Russian sources (202) claimed that the main goal of the Zond-2 mission had been a flyby of Mars and a close-up photography of the planet, rather than a fiery crash into its surface. According to one Russian source, due to inability to conduct a trajectory correction maneuver, Zond-2 passed 650,000 kilometers from Mars. (202)

It is still possible that the exact flight scenario was changed at the last minute, but half a century after its launch most details about its mission remain a mystery.

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Article by Anatoly Zak; last update: November 30, 2014

Page editor: Alain Chabot; last edit: November 30, 2014

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