What it was: A derivative of the Soyuz capsule designed for a manned lunar flyby. Two cosmonauts would be sent in a six-day, figure-8 loop around the Moon and then back to Earth. It was initially proposed to get a cosmonaut to the Moon by 1967 (though more realistically by the end of 1968), before the Americans could land there and even before they could do a manned flyby themselves. By the time it was being developed the USSR had no realistic chance of beating the US to a Moon landing, so this was their last chance to make Kennedy’s Moon challenge a draw.
It should not be confused with Zond 1 through Zond 3, which were unrelated robotic lunar and planetary probes. The manned craft started with Zond 4, and it was the first to actually use that resurrected name (which simply means “Probe” in Russian) despite several tests of other similar and identical craft before its launch.
Details: The 1964-65 tug of war over the Soviet manned space program was finally resolved a few months prior to the passing of Sergei Korolev. Unfortunately, it wasn’t resolved to anyone’s satisfaction and signs are that Korolev would have continued to chip away at his rival Vladimir Chelomei if the former hadn’t died on the operating table in January of 1966.
That having happened, the USSR was left with two manned Moon programs that didn’t quite mesh with one another. The 7K-LOK/LK was the Soviet Union’s answer to the Apollo program: it was a Soyuz derivative mated with a one-man lander (the LK) comparable to the American CSM/LM combination that culminated in Apollo 11. It was to be launched on the closest thing the Russians had to a Saturn V too, the N1.
But while the United States was working up to Apollo 11 with a flyby using the same craft and the same rocket (leading to the first manned flyby of the Moon, Apollo 8 on December 24, 1968), the Russian flyby program remained independent thanks to the fight between the two Soviet designers. Korolev mostly held the field by early winter 1965, but while Chelomei’s parallel flyby craft, the LK1, had been shunted to the sidelines the launcher had stayed in his hands. The UR-500 was a completely different rocket from the N1: different designer, different fuels, different engines. While it would eventually become the highly successful Proton booster that Russia still uses today, it didn’t provide any data on how the N1’s various stages would work. As such, using it was a distraction from the Moon landing, not a help like the American flyby program was to their eventual landing.
Furthermore the UR-500 was a much less powerful rocket, which meant that the 7K-LOK/LK combination absolutely couldn’t be launched on it. Even stripping out the LK lander from the arrangement and just testing the 7K-LOK wasn’t possible—even that was too heavy. As a result, Korolev’s OKB-1 (renamed TsKBEM two months after his death, as part of a reorganization under his lieutenant and successor Vasili Mishin) was tasked with building a smaller flyby craft that the UR-500 could get off the ground. They did manage to make it into a relative of the 7K-LOK by once again returning to their basic Soyuz setup, but the resulting 7K-L1 is probably the weirdest variant in that entire family of spacecraft.
A basic Soyuz consists of three pieces. At its base is a cylindrical support module containing electrical equipment and the propulsion system. At the opposite end is the spherical habitation section, which houses the crew in orbit. In the middle is the acorn-shaped re-entry module, in which the crew sits during launch and re-entry; when re-entering the Soyuz breaks into its three constituent pieces and the re-entry module is the one that brings the cosmonauts home.
In order to bring the weight of the 7K-L1 down to acceptable levels, its engineers deleted the habitation module and its 60% of the living volume in the vanilla Soyuz. During the week-long flyby of the Moon, its crew of two would have to live entirely in the re-entry module, which had a grand total of four cubic meters of space. Also removed were the reserve parachute, and enough fuel to actually orbit the Moon (as Apollo 8 did, ten times). The Russian mission would be a quick loop around and back, and then the re-entry capsule would be skipped off the Earth’s atmosphere and aimed at the Kazakh SSR. Even if the skip maneuver failed, it would still land safely in the Indian Ocean; the Soviet Union developed naval assets for the specific purpose of retrieving cosmonauts who went off-course that way.
Design decisions driven by weight aside, by the spring of 1967, the 7K-L1 was ready for its first test. Contrary to their reputation, the USSR has always been keen to test their systems unmanned in space before committing a human being to them. When Apollo 8 was launched as a manned mission, the Russians were by all accounts shocked that their rivals would put men aboard their craft the very first time it left Earth orbit. Unlike their Soviet counterparts, the Americans felt that their system was safe already, and one can judge them on the fact that of the eleven manned missions using some combination of the CSM and LM only Apollo 13 had a serious failure.
Less confident, the Soviets launched their first prototype 7K-L1 craft on March 10, 1967. As they were wont to do, the Russians hid its nature behind the generic name they used for space missions, Cosmos. Cosmos 146, as this launch was called, was even aimed away from the Moon to allay suspicions, as the necessary testing could be done so long as the craft went somewhere approximately away the Moon’s distance away from the Earth. Its destination in deep space was explained as simply being an exploration of the conditions far away from our atmosphere and magnetic field.
Cosmos 146 was a success, and the Russians went on to more complex testing with the aim of flying two cosmonauts by the Moon in either June or July 1967.
What happened to make it fail: That stated goal wasn’t dictated by anything realistic, but rather a desire to make a big splash prior to the fiftieth anniversary of the October Revolution. This was part of a general pattern of unattainable goals imposed on TsKBEM under its new, insecure leader Vasili Mishin.
That pressure led to several large failures in the period immediately following Cosmos 146, not all of them directly related to the Zond program but helping to demonstrate how the entire Soviet space program was in disarray following the death of Sergei Korolev:
- The second Zond test, Cosmos 154, was launched on April 8, 1967, but its translunar injection stage failed on April 10 and it was stuck in Earth orbit.
- Soyuz 1, the first manned Soyuz in Earth orbit, had several serious systems failures one of which (the parachute system) ending up killing cosmonaut Vladimir Komarov on April 24. All derivatives of the Soyuz fell under suspicion after this.
- After a considerable delay caused partly by Komarov’s death, on September 27 another Zond was launched. This test failed after its Proton booster’s first stage had an engine failure.
- November 22 saw yet another try, and this time the second stage of the Proton failed to ignite properly.
- Zond 4, was launched on a “lunar distance but not near the Moon” journey like Cosmos 146 and was a much-needed partial success. Unlike Cosmos 146, though, it was designed to re-enter, but when it tried on March 10, 1968 it failed to execute its skip maneuver properly. Rather than let it land in the Gulf of Guinea where it might have been retrieved (or even seen) by someone other than Soviet personnel, it was sent a self-destruct signal a few minutes before splash-down.
The success of Zond 4, besides belatedly earning the program a name, was enough for the USSR to move on to trying to fly biological specimens around the Moon as a final test before committing cosmonauts to a flight. The first two tries at this in April and July failed. The former had the Zond signal that its booster had failed when it hadn’t—it was in the middle of its second stage-burn—and “rescue” itself by separating and flying away on its launch escape system. The latter was even worse: four days before the mission was scheduled to go the oxidizer tank on the Zond’s translunar injection stage exploded, killing one person. It took two weeks to disentangle the Zond and the remainder of the rocket (both of which were recoverable) as it tipped over into the launch tower and was partially fuelled with the toxic propellants used by the Proton, and further tests had to be pushed back.
Zond 5 was next up, and on September 15, 1968 it executed the sole successful lunar flight of a Zond prior to the Apollo moon landings. It took the first living things (plants, drosophila fruit flies, and two tortoises) to the Moon and back, beating Apollo 8 and its biological cargo of three human astronauts by three months. The sole main failure of the flight was an inability to pull off a skip trajectory again, but the capsule was successfully recovered from the Indian Ocean and the tortoises and other cargo shipped back to the USSR.
With Zond 5 under their belts, the Soviets felt sufficiently happy with their progress to decide on three possible two-man crews for the first manned mission to the Moon. In another world we might be discussing Alexei Leonov and Oleg Makarov in the same sentences and Armstrong and Aldrin. But the Russians wanted one more “biological” test success before moving on, and didn’t get it. Zond 6 depressurized a few hours before re-entry, then its parachute failed to open. The next three attempted launches had their Proton fail instead. The last of these was sent up just prior to Apollo 11, and from then on the Zond program was running on vapours: the US had beaten them to the Moon in both possible ways, and the USSR’s leadership were concerned that both the Zond flybys and the N1 single-man lunar lander would look feeble in comparison even if they succeeded in every detail. All planned manned flights of Zond were cancelled in March 1969, though Vasili Mishin did keep flying them on more automated flights until all the built Zonds remaining were used up, in the hope that someone would change their mind.
Zond 7 flew from August 7 to 14, 1969, and if manned would have successfully sent two cosmonauts on a trip to the Moon and safely return them. Zond 8 would have done the same in September of 1970. But the program had its orders: both were unmanned.
What was necessary for it to succeed: There was a short window between the Apollo 1 fire on January 27, 1967 and Vladimir Komarov’s death in April of the same year where it looked as if the Soviet Union had an opportunity to beat the US to a flyby. Instead everything went wrong for them after Cosmos 146, while the US successfully sorted out what was wrong with their program by the flight of Apollo 7 in October of 1968.
If TsKBEM and the builders of the Proton had somehow been able to resist the pressure to try and go from the first unmanned prototype test in February 1967 to a manned lunar flyby no later than July and biweekly manned missions in August, September, and October, then they had a chance. Instead they were held to an insane schedule for propaganda reasons, one which they knew was impossible even at the time. That pressure led directly to repeated failures and disarray, even though both the Soyuz and the Proton that kept failing them eventually became highly successful pieces of equipment. While they were able to return to a more normal pace after the fiftieth anniversary of the Revolution in November 1967, the program never recovered from the shortcuts that had been built in to try and reach that date.
While it was far from a sure thing, if it had been given a more realistic (though necessarily quick) pace from the beginning, Zond certainly could have taken two Soviet cosmonauts around the Moon before Apollo 8, giving the USSR one last laurel before Apollo 11: the final 1968 launch window from Baikonur to the Moon was from December 8 to December 11, as much as thirteen days before the Americans could and did go. Instead they ended up with a second batch of space tortoises in August 1969.
A composite video of pictures taken by Zond 8 as it flew around the Moon can be found on YouTube. It gives us a close an idea as is possible of what hypothetical cosmonauts aboard would have seen during their mission—except that, as well as not having a habitation module or a reserve parachute, the Zond didn’t have any windows either.