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Zond ( Russian Зонд , pronunciation [ ˈzɔnd ], also known as Sond in German ) is the name of a series of Soviet space probes from 1964–1970. The missiles Zond 1 to 3 had their origin in the project of a common space probe type for missions to Venus and Mars . Zond 4 to 8 were unmanned tests of the command module of the Soviet manned lunar program .

This heterogeneous program was a special feature of the Zond missiles, which had a largely identical structure. On the one hand, they were used for experimental purposes (for example, orbit maneuvers or tests for landing approach techniques), and on the other hand, to disguise the preparations for the manned moon landing . Because the beginnings of moon flights (since 1959) were accompanied by many failures of both superpowers, which the Soviet Union - in contrast to the USA - sought to conceal. The “unofficial” tests to prevent further false starts, silent probes or unsuccessful orbit and landing maneuvers were therefore bundled in the Zond program from 1964 onwards.

In accordance with this policy, the flights to Venus and Mars, for example, were initially only announced, they served to explore interplanetary space . After the success of the Apollo missions, the only incompletely known probe program in the West was discontinued in 1969/70.

The planetary probes

Zone 2
  • Kosmos 21 (launched on November 11, 1963 with a Molnija rocket ) was the technological prototype of the new space probes. It had a 270 kg landing capsule and was supposed to be brought into an orbit-like solar orbit with an inclination of 5 degrees to the ecliptic . After half a year, the probe should come back close to the earth and then put the capsule down on a test basis. That would have been the first object to return from space at second cosmic speed . In government documents, the probe was referred to as an object probe . Due to the failure of the fourth stage, Block-L, the probe remained in earth orbit and could not fulfill its task.
  • Kosmos 27 (launched on March 27, 1964 with a Molnija rocket) was a space probe to Venus. It was identical to Zond 1, but only reached earth orbit and was therefore given a cosmos camouflage designation. In addition, another engineer test ( object probe) of the new space probe should take place on February 19, 1964 ; the launcher failed, however, so that no earth orbit was achieved.
  • Zond 1 (launched on April 2, 1964 with a Molnija rocket) was also a space probe to Venus. Like Kosmos 27, it was supposed to drop a landing capsule that was supposed to hit Venus. The skin body of the probe leaked when the glass window of a star / solar sensor on the orientation system broke. The demhermetization triggered a short circuit in the probe, which destroyed the transmitter of the probe. Contact with the country's own radio system was lost on May 25, 1964. Two orbital corrections were automatically performed by timers at 560,000 kilometers and 13 to 14 million kilometers from Earth. These were the first successful orbit corrections on a Soviet interplanetary space probe. On July 19, 1964, the dead probe passed Venus at a distance of 110,000 kilometers.
  • Zond 2 (launched on November 30, 1964 with a Molnija rocket) was a Mars probe that was supposed to fly past the Red Planet and take measurements and photos. However, one of the two solar panels did not unfold, so the power supply became increasingly critical as the distance from the sun increased. On May 14, 1965, radio contact with the probe was lost. On August 6, 1965, the silent probe passed Mars only 1,500 km away.
  • Zond 3 (launched on July 18, 1965 with a Molnija rocket) was originally planned as a Mars probe , but was sent to the moon due to launch delays and the closing of the Mars launch window . She tested a camera system and other experiments while flying past the moon (9200 km away). The probe then delivered data from interplanetary space from a distance of 153.3 million km .

The lunar probes

Illustration from Zond 4 to 8

Zond 4 to 8 were largely identical probes with launch masses of 5140 to 5390 kg, which were launched with a four-stage version (UR-500K, GRAU index 8K82K) of the Proton rocket with the Blok-D (GRAU index 11S824) as the upper stage . With effect from December 25, 1965, the original orbit project UR-500 / LK-1 ( OKB-52 from Tschelomej ) was transferred to the UR-500 / L1 project and thus went largely to the OKB-1 research group of rocket pioneer Sergei Koroljow over. The spaceship was now a special version (7K-L1) of the Soyuz spaceship, derived from the Soyuz A spaceship of the manned lunar program , which should first be tested unmanned.

They were put on a train that went around the moon and back to earth. A first short entry into the atmosphere should take place over the southern hemisphere and slow down the speed by aerobraking so that a controlled and tolerable final entry with a landing in the usual area in Kazakhstan was possible. Because of the lack of exact orbit data after the South Pole Dip, precision landings were not possible. An alternative, more precise return profile with initial entry over the North Pole and splashing in the Indian Ocean was also tested. Both profiles require a very precise return from the moon and very precise position control of the return part. These problems were ultimately resolved. The manned moon flights were originally planned to take place between August and October 1967 in honor of the 50th anniversary of the October Revolution . Ultimately, the unmanned part of this program was completed with a three-year delay and the flight qualification of the system.

  • Zond 4 (s / n 6L): launched on March 2, 1968 with a Proton K rocket, after a deep-space flight (probably for "reasons of secrecy" the orbit was offset by 180 ° from the moon), when re-entering the descent corridor, it was very precise one, but a star sensor failed, making an exact attitude control for the two-part descent impossible. The subsequent purely ballistic descent with loads of up to 20 g would have led to a landing in Africa. Zond 4 was automatically blown up at a height of 10 to 15 km over the Gulf of Guinea .
  • Zond 5 (s / n 9L): launched on September 15, 1968 with a Proton-K rocket, also deviated from course, but was recovered after a direct ballistic descent in the Indian Ocean. A crew could have survived this flight (possibly with injuries). The overall successful test of the capsule, which also contained insects and other smaller living things, led NASA to move forward to orbit Apollo 8 .
  • Zond 6 (s / n 12L): launched on November 10, 1968 with a Proton-K rocket, crashed into a hard landing in Kazakhstan. The planned two-part descent succeeded for the first time. The return capsule was already decompressed during the return flight from the moon . A crew without spacesuits (this was planned in order to save weight) would not have survived this disturbance. The decompression led to problems in the on-board electronics due to the lack of cooling under vacuum. The main parachute unfolded much too early and was dropped at a great height (approx. 5000 m). Ultimately, the malfunction of the parachute system was also due to the defects following the decompression. A crew wearing spacesuits would at least not have survived the crash. However, a film cassette with images of the moon and the earth was recovered. The hard landing took place with the best precision of the entire program, only 16 km from the target point and approx. 75 km from the starting point.
  • Zond 7 (s / n 11L): launched on August 7, 1969 with a Proton-K missile, was probably the only fully successful mission within the Zond-4-8 program. The soft landing south of the Kazakh city of Kustanai occurred with a deviation of 47.5 km from the planned touchdown point. One turtle on board survived the seven-day flight without food or water. This flight was the only one in the entire program that a crew would certainly have survived without damage. At this point, however, the first US Apollo 11 moon landing mission was successfully completed.
  • Zond 8 (s / n 14L): launched on October 20, 1970 with a Proton K rocket, contrary to popular belief, it did not go off course. This mission, which was normally no longer approved after successful US moon landings, tested an alternative return profile for the N1-L3 program, which was still running at the time, and, after a first aerobrake over the North Pole, went as planned in the Indian Ocean with a deviation of around 25 km from the target point low. The spacecraft was recovered within 15 minutes of being ditched by the Taman ship . However, no further details are known about the watering and salvage conditions. A crew could probably have survived this flight unscathed. The advantage of this alternative return path lay in the precise recording of path data from radar stations on Soviet territory after the first entry. This made it possible to precisely determine the final landing location and / or, after a correction using these data, for the second section, precision landings. However, these waterings then took place outside the territory of the USSR.

In addition to these officially named Zond probes, there were also five false starts in the Zond program. The first start of the entire system took place under the code name Kosmos-146 on March 10, 1967.

During the preparations for launching the Zond with the serial number 8L on July 14, 1968, a tank of the Proton rocket was mistakenly pressurized too high. The tank burst and debris from the partially fueled rocket fell into the launch tower. A member of the ground staff was killed. It took over two weeks to remove the explosive debris from the launch tower.

Two remaining Zond capsules (s / n 10L and 15L) were preserved, never took a flight and today, as museum pieces, are the last remaining hardware in this program.

See also

Web links

Commons : Zond program  - collection of pictures, videos and audio files

Individual evidence

  1. ^ Bart Hendrickx: Managing the News: Analyzing TASS Announcements on the Soviet Space Program (1957–1964). In: Quest, Vol. 19, No. 3, 2012.
  2. Asif Siddiqi: Deep Space Chronicle NASA SP-2002-4524. Washington, June 2002, p. 42.
  3. Alain Chabot: Mission L1 No. 8L: A deadly accident. In: russianspaceweb.com. July 14, 2018, accessed on July 20, 2020 .