Зонд-5: Первый облет Луны с животными на борту

1968 Soviet spaceflight to circle the Moon, first lunar mission to carry animals

| orbit reference = Geocentric
| orbit regime = Low Earth
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| orbit eccentricity = 0.00604
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| orbit inclination = 51.83°
| orbit period = 89.29 minutes
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| orbit epoch = 13 September 1968
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| apsis = gee

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| programme = Zond
| previous mission = Zond 1968B
| next mission = Zond 6

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Zond 5 (Зонд 5) was a spacecraft of the Soviet Zond program. In September 1968 it became the first spaceship to travel to and circle the Moon in a circumlunar trajectory, the first Moon mission to include animals, and the first to return safely to Earth. Zond 5 carried the first terrestrial organisms to the vicinity of the Moon, including two tortoises, fruit fly eggs, and plants. The Russian tortoises underwent biological changes during the flight, but it was concluded that the changes were primarily due to starvation and that they were little affected by space travel. The Zond spacecraft was a version of the Soyuz 7K L1 crewed lunar flyby spacecraft. It was launched by a Proton K carrier rocket with a Block D upper stage to conduct scientific studies during its lunar flyby.

Out of the first four circumlunar missions launched by the Soviet Union there was one partial success, Zond 4, and three failures. After Zond 4's mission in March 1968, a follow up, Zond 1968A, was launched on 23 April. The launch failed when an erroneous abort command shut down the Proton rocket's second stage. The escape rocket fired and pulled the descent module to safety. In July, Zond 1968B was being prepared for launch when the Block D second stage rocket exploded on the launchpad, killing three people, but leaving the Proton first stage booster rocket and the spacecraft itself with only minor damage. The Zond 5 mission was originally planned to fly cosmonauts around the Moon, but the failures of Zond 1968A and Zond 1968B led the Soviets to send an uncrewed mission instead, from fear of the negative propaganda of an unsuccessful crewed flight. Soviet scientists chose tortoises since they were easy to tightly secure. There were also two tortoises used as control specimens and four more in a vivarium. Twelve days before launch, the two space bound tortoises were secured in the vehicle and deprived of food and water; the control tortoises were similarly deprived. The food deprivation was a part of pathomorphological and histochemical experiments. The biological payload also included fruit fly eggs, cells of wheat, barley, pea, pine, carrots and tomatoes, specimens of the wildflower species Tradescantia paludosa, three strains of the single celled green algae Chlorella, and one strain of lysogenic bacteria. The Russian Academy of Sciences stated that a mannequin equipped with radiation sensors occupied the pilot's seat. Zond 5 also contained proton detectors. Zond 5 could transmit some of its data back to ground stations, although data stored onboard and collected after return to Earth has less noise.

Zond 5 launched on 14 September 1968 at 21:42.10UTC, from Site 81 at the Baikonur Cosmodrome. The thrust of the third stage rocket was terminated at , which was the start of a 251 second coast. Block D, the upper stage rocket, ignited and burned for 108 seconds, placing the spacecraft into a parking orbit of Fifty six minutes into the parking orbit the Block D fired a final time for the trans lunar injection. The closest distance was It landed at −32°38' latitude and 65°33' longitude, from the nearest Soviet naval ship. The landing occurred at night, which impaired recovery efforts. Zond 5 became the first spacecraft to circle the Moon and return to Earth. The entire journey took 6days, 18hours and 24minutes. Although the ballistic reentry would probably have been lethal for human occupants, it did not appear to affect the biological specimens, which were alive when the descent module was opened four days after landing. but left shortly after the spacecraft was brought on board the Soviet ship.

High quality photographs of the Earth, the first photos of their kind, were taken at a distance of
In October 1968, sources in the U. S. claimed the mission was not as successful as the Soviets advertised. The mission had been intended to fly closer to the Moon, and its actual distance did not allow for useful lunar photography. They also said that the angle at which the spacecraft reentered the atmosphere was too steep for a cosmonaut to survive. The sources indicated that the spacecraft landed in the Indian Ocean when the planned location was in Soviet territory, which was a factor in the recovery taking ten hours. The official Soviet news agency, TASS, announced in November 1968 that the flight carried living animals. The tortoises were dissected on 11 October after fasting for 39days. The flying tortoises, identified as and , had lost 10% of their body weight during the trip, but showed no loss of appetite. The control tortoises lost 5% of their weight. Comparison of analyses of blood from the space travelling tortoises and the control specimens revealed no differences. Another analysis showed the flying tortoises had elevated iron and glycogen levels in their liver and that the flight also affected the internal structures of their spleens. The authors concluded that the changes in the flight tortoises were primarily due to starvation, with the space travel having little effect. In November 1968, it was announced that the spacecraft was planned as a precursor to a crewed lunar spacecraft. The Soviets made this announcement a month before the planned Apollo 8 flight, in an attempt to show they were close to being able to carry out a crewed trip to the Moon.

The Zond 5 caused a scare in the United States when on 19 September 1968, the voices of cosmonauts Valery Bykovsky, Vitaly Sevastyanov and Pavel Popovich were transmitted from the spacecraft and intercepted by Jodrell Bank Observatory and the CIA. The cosmonauts were apparently reading out telemetry data and computer readings, and even discussing making an attempt to land. At the height of the Cold War, there was a real concern that the Soviets might actually beat NASA to the Moon. Apollo 17 astronaut Eugene Cernan remarked that the incident had "shocked the hell out of us." Popovich would later recall: "When we realized we would never make it to the moon, we decided to engage in a little bit of hooliganism. We asked our engineers to link the on the probe receiver to the transmitter with a jumper wire. Moon flight missions were then controlled from a command centre in Yevpatoria, in the Crimea. When the probe was on its path round the Moon, I was at the center. So I took the mic and said: "The flight is proceeding according to normal; we’re approaching the surface " Seconds later my report – as if from outer space – was received on Earth, including [by] the Americans. The U. S. space advisor Frank Borman got a phone call from President Nixon [actually Johnson], who asked: 'Why is Popovich reporting from the moon?' My joke caused real turmoil. In about a month's time. Frank came to the USSR, and I was instructed to meet him at the airport. Hardly had he walked out of his plane when he shook his fist at me and said: 'Hey, you, space hooligan!'"

The Zond 5 capsule is on display at the RKK Energiya museum, located in Moscow Oblast, Russia.