At the very end of 1968, Soviet scientists were going to carry out the world's first manned flyby of the Moon aboard the Zond-7 spacecraft. As part of the "moon race" it was important to get ahead of the Americans.
The split of chief designers
Among the Soviet chief designers, there was no consensus on the development of the space program. Lunokhod designer Georgy Nikolaevich Babakin said that only automatic space exploration can bring immediate success. Sergei Pavlovich Korolev insisted on the development of manned programs. And Vladimir Nikolaevich Chelomey (one of the key creators of the USSR nuclear missile shield), on the one hand, shared Babakin's view, and on the other, in defiance of Korolev, proposed his own version of the lunar ship and launch vehicle. But in 1964, Khrushchev, who patronized Chelomey, was removed from power, and Korolev was entrusted with the lunar manned program.
Politics and Science
Unfortunately, the decisions made by Soviet officials during the "moon race" were not dictated by common scientific sense. It was important not to fly around the moon in a manned spacecraft, but it was important to do it faster than the Americans! The Soviet lunar manned program became public only in the 90s, before that, for political reasons, it was kept secret. This approach was partly a consequence of the belated decision to join the "lunar race" and hardly contributed to the purposefulness of problem solving.
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Organizational mistakes
The excitement around the "moon race" made it difficult to make informed decisions. Officials instructed different design bureaus to simultaneously deal with the same tasks, which resembled an attempt to solve in quantity, not quality. In fact, there were two manned lunar programs: a lunar flyby and a lunar landing, although it is clear that the first is a special case of the second. And in theory, a manned flyby of the moon should be a stage of preparation for a manned lunar landing. The fact is that a booster rocket with which you can fly to the Moon and back is also suitable for flying around it, but not vice versa. Landing requires a ship of a different design with a greater mass, which means that the launch vehicle must have a greater pulling force, but it is more difficult to build such a rocket. Therefore, in the USSR, they worked in parallel on both of them in the hopethat at least something will work out.
Financing
Funding was an important and "sore point" issue. Savings in the space industry are irrelevant. The half-heartedness of the position led to the fact that they decided to finance a cheaper project: the royal carrier rocket N-1 ("Carrier-1"), which was almost the main reason for the failure.
Launch vehicle "N-1"
The rocket was developed under the leadership of Korolev. But in 1966, Sergei Pavlovich died and after his death, the project was entrusted to the designer Vasily Mishin. Who knows, maybe if Korolev had completed his project, then everything would have worked out, but fate decreed otherwise. N-1 is a super-heavy launch vehicle. It was intended for launching a heavy ship into outer space. The rocket consisted of five blocks: A, B, C, D and D. The first three stages had to overcome the force of gravity and reach the near-earth orbit, two more - to "drive" the ship to the Moon and back. It was decided to put people in the ship in the case of three successive automatic flights, but all four starts of the N-1, alas, failed. Twice - February 21, 1969 and July 3 of the same year - as part of the lunar flyby program and twice - on June 27, 1971 and November 23, 1972 - as part of the lunar landing program, the H-1 carriers exploded for various reasons without flying too far. And at the second launch, the launch vehicle fell flat on the launch site at 23 seconds from the start of the launch, which led to the largest accident in the history of rocketry at that time.
Launch vehicle "Proton"
After the first two unsuccessful launches, the N-1 was sent for revision and again turned to Chelomeev's Proton, which had less tractive power, but flew, although not always. For a manned lunar landing, the traction force of the "Proton" is not enough, but for a flyby around the natural satellite of the Earth it was enough. It was the carrier rocket "Proton" that was supposed to send Soviet cosmonauts Bykovsky and Rukavishnikov (according to other sources Leonov and Makarov) to the moon on December 8, who were ready to board the ship and were waiting for an order. But the risk was too great, because at that time, not a single ideal flight took place within the framework of the program. A wise decision, the start was canceled and it was appointed a month later - only without the astronauts. The fears were confirmed: the launch vehicle exploded at launch. In fairness, we notethat the descent vehicle was returned to Earth by the emergency rescue system (SAS), which meant the rescue of the astronauts in the event of their participation in the launch. True, during the month that separated these events, the Americans launched their spacecraft to the Moon with three cosmonauts (for comparison: our ship is two-seater) and made ten triumphal orbits around the Moon. The meaning of the lunar flyby program disappeared, and soon it was closed.
"Probe" and "Soyuz"
The Zond series of spacecraft, as part of the manned lunar program, was based on the proven Soyuz spacecraft. The sad experience of unsuccessful launches (there were more than a dozen of them, but only one completely successful: August 8, 1969) made it possible to work out the emergency rescue system, which almost always worked satisfactorily. There would be no happiness, but misfortune helped! One way or another, but the scientists did their job and the Soyuz ships are still considered one of the most reliable, which is remarkably shown in the sensational Hollywood science fiction film Gravity.