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L1 No. 4L: Not getting too far

Reeling from the disastrous mission of Soyuz-1, Soviet engineers at the TsKBEM design bureau began the return-to-flight efforts with an attempt to launch an unmanned version of the 7K-L1 circumlunar spacecraft to test the first fully operational version of the vehicle. It would be also the sixth launch for the UR-500 rocket and the third launch for its UR-500K variant, developed specifically for human missions around the Moon. However the launch attempt on Sept. 28, 1967, lasted only a minute and a half...

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The 7K-L1 No. 4L vehicle (a.k.a. Zond) lifted off on Sept. 28, 1967.

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The 7K-L1 No. 4 mission at a glance:

Spacecraft designations 7K-L1 (11F91) No. 4L
Launch vehicle 8K82K (UR-500K, Proton-K) No. Ya10722901 / Block D1 (11S824) (No. 12L)
Launch site Tyuratam, Site 81, "Left" pad
Crew Unmanned
Spacecraft mass 5,017 kilograms
Launch date and time 1967 Sept. 28, 01:12 Moscow Time
Mission results Failure at T+97.4 seconds during Stage I ascent


While Soyuz is grounded

The active preparation work on Vehicle No. 4L for the L1 circumlunar program apparently began at the beginning of 1967, after delays with supplies of components for the mission had prevented the beginning of the work on December 20, 1966. Around that time, the delivery of critical avionics for Vehicle No. 4L from NIIAP in Moscow was scheduled for Jan. 20, 1966.

On February 13, 1967, the head of TsKBEM Vasily Mishin wrote down new milestones for the delivery of the ship's key modules to the Checkout and Testing Station, KIS, where the spacecraft was to undergo final preparations before its shipment to the launch site. The Block D space tug for the mission was expected to arrive on February 26, followed by the descent module and the instrument module two days later. However TsKBEM's sub-contractors were still late with various components, which pushed the preparations of Vehicle No. 4L further behind schedule.

Because Vehicle No. 4L would be the first L1 mission intended to return to Earth, the search and rescue services, PSK, also had to be ready, especially in case of the landing at sea. Also, in the wake of a launch accident in December, the interfaces between the flight control system, SU, and onboard measuring network, SBI, in the spacecraft had to be changed to account for newly discovered problems.

On April 4, Mishin finally mentioned Vehicle No. 4L in the context of testing. His later notes quoting his colleagues indicated that all the components for the 7K-L1 Vehicle No. 4L had been delivered for assembly at the TsKBEM design bureau on April 10, 1967.

As of April 30, Mishin had the following launch schedule for the UR-500K-L1 project in his notes:

Vehicle Launch date Crew
4L June 15-20 Unmanned
5L July 1-5 Unmanned
6L July 15-17 Unmanned
7L Aug. 1-5 Unmanned

Vehicles No. 8L, 9L and 10L were expected to fly around the Moon with crews onboard. That schedule apparently held only for a few days. On May 5, engineers began testing the fully assembled Vehicle No. 4 at KIS in Podlipki near Moscow. However on the same day, Mishin prepared an updated launch schedule for the 7K-L1 project to be presented at the meeting of the Chief Designers Council on the Soviet circumlunar project, apparently chaired by Dmitry Ustinov:

Vehicle Launch date Crew
4L (No. 229) June 17-19 Unmanned
5L (No. 230) June 27 - July 5 Unmanned
6L (No. 231) July 12-17 Unmanned
7L (No. 232) July 25 - Aug. 3 Unmanned
8L (No. 233) Aug. 15 - 20 Manned

If the first four flights went as scheduled, the fifth vehicle (No. 8L) could carry the first pair of cosmonauts around the Moon, as early as August but no later than November 7, 1967, the 50th anniversary of the Bolshevik Revolution. This timeline looked wildly optimistic, especially after the Soyuz-1 disaster. To fulfill it, Mishin needed two teams of test engineers and two processing facilities for the L1 spacecraft at KIS.

To provide tracking and communications for the fully operational L1 spacecraft, Mishin planned to deploy the Ilichevsk (PTK NII-4) tracking ship in the Atlantic Ocean off the coast of Cuba beginning with mission No. 4L. However, the development of the DRK deep-space communications system for the L1 project still lagged behind schedule.

On May 22, Minister Sergei Afanasiev directed Mishin to schedule a Chief Designers Council meeting for the 7K-OK and 7K-L1 projects.

As of May 23, Mishin planned a number of tests to support the L1 project: one descent module prototype designated E3091 would be dropped from an aircraft to test a new parachute container redesigned in the wake of the Soyuz-1 accident. Vehicles E3090 No. 1 and No. 2 would be used to test the Emergency Escape System, SAS. As a result, the 4L and 5L vehicles were expected to be equipped with new parachute containers.

On May 31, the State Commission overseeing the launch of Vehicle No. 4 finally convened. Mishin recorded Evgeny Shabarov's report that test activations of the L1's telemetry systems had revealed 24 issues, 10 of which had still remained opened. There were the usual problems with the deep-space communications network and issues with solar and star-based attitude-control sensors. It seems that by June 2, sensors 99K, 100K and 101K were replaced, but they required more tests. On June 10, Mishin even planned to call a member of the Central Committee of the Communist Party Sergei Zverev to use his influence to expedite the delivery of replacement sensors for Vehicles No. 4L and 5L.

The State Commission meeting on May 31 also reviewed the status of assembly of the follow-on L1 vehicles No. 5L, 6L and 7L.

On June 2, 1967, specialists working at KIS finally completed powering-up on Vehicle No. 4L.

With all the time required for the post-Soyuz-1 recovery, Mishin apparently had another major review of the L1 project on June 16. The Head of the State Commission Georgy Tyulin and key flight-control specialists Nikolai Pilyugin and Mikhail Ryzansky were apparently present. They discussed multiple problems, including many errors in the installation of the onboard cable lines, BKS, on the spacecraft and various issues with integration of avionics. Mishin's deputy for testing Evgeny Shabarov reported that only three out of 13 integrated tests had been conducted at the time.

By then (June 16), the launch schedule looked as following:

Vehicle Launch date Mission
4L (No. 229) July 25 - Aug. 3 Unmanned
5L (No. 230) Aug. 15 - Aug. 20 Unmanned
6L (No. 231) Aug. 24 - Aug. 30 Unmanned
7L (No. 232) Sept. 15 - Sept. 20 Unmanned
8L (No. 233) Oct. 22 - Oct. 25 Manned

Not surprisingly, this schedule could not be met as well.

Another review of the L1 among many other projects took place on June 20, where Mishin apparently received the mass budget for the L1 spacecraft from his deputy Konstantin Bushuev. He also scheduled the completion of technical specifications for the parachute system of the 7K-OK and L1 spacecraft by June 25. Mishin also asked Yuri Semenov, then a key engineer responsible for the L1 project, to write him a general review on the status of the 7K-L1 project. Mishin's other deputies Evgeny Shabarov and Bushuev also had to write similar accounts of the development work and Boris Chertok had to report on all changes in the avionics. Finally, Georgy Degtyarenko had to outline the situation with upgrades to Block D. The documents for flight testing covering missions from 4L to 8L were also being prepared.

From Mishin's records made on June 21, it is clear that the 7K-L1 No. 4L spacecraft still remained at the Control and Checkout Station, KIS, besieged by technical problems. Three days later, Mishin noted the delivery of the final set of hardware for Vehicle No. 4L. The new schedule seemingly approved by Mishin aimed for the shipment of the spacecraft to the launch site by July 15, 1967.

In parallel, TsKBEM was working on the second test facility for the L1 spacecraft inside KIS and preparing an action plan for upgrades to the launch and processing facilities needed for manned missions of the L1 vehicles beginning with Vehicle No. 8L.

On July 18, Mishin made a few notes on the preparation for the Chief Designer Council meeting dedicated to the L1 project, which apparently took place the same day. The testing of the Vehicle No. 4L at KIS in Podlipki had been completed two days earlier, on July 16, and the shipment of the spacecraft to Tyuratam was now scheduled for between July 25 and 27. The spacecraft would be preceded to the launch site by its Block D stage scheduled for departure on July 22, 1967.

At the meeting, Yevgeny Shabarov reported that TsKBEM had been working on the delivery of the operational documentation for the L1 spacecraft, in time for the final round of testing at the launch site. The documents were updated to take into account the latest results of the tests at KIS.

According to Nikolai Pilyugin, who oversaw the development of the flight control system, the main problems during the assembly of Vehicle No. 4L dealt with computer failures during autonomous tests. Also, several areas vulnerable to interference were discovered during integrated tests at KIS. After working for 200 hours, one channel of the main BTsVM computer failed and had to be replaced. Fortunately, at the meeting, Pilyugin cleared the computer for further operations.

August 1967: Preparations in Tyuratam

On August 3, Shabarov gave Mishin a work plan detailing the preparations of the Vehicle No. 4L in Tyuratam. According to a representative of military test personnel named Patrushev quoted by Mishin, the processing of Vehicle No. 4L began in Tyuratam on August 2, however the first 10 days were spent on the completion of the factory assembly rather than the processing and testing. Only 24 days were allocated for testing at the launch site, but it would ultimately take much longer, because of various technical issues, first of all a short circuit in the onboard cabling system, BKS, and problems with the long-range communications system, DRK. Various technical issues, including a failure of the S166A avionics system, required the spacecraft to be taken apart twice. There was also a failure of the Mir-3 tape-recording mechanism, a cable break, a failure of a fan in the descent module and loss of pressure in the parachute hatch.

According to notes made by Mishin on Aug. 18, 1967, the launch of Vehicle No. 4 had been scheduled between Sept. 13 and Sept. 15, 1967.

Around the same time, the various missions in the L1 project had the following status:

Vehicle Launch date
4L (No. 229) Launch between Sept. 13 and 15, 1967 (The vehicle is already in Tyuratam)
5L (No. 230) Shipment to Tyuratam at the end of August (?) (Vol. 2, p. 34)
6L (No. 231) Delivery to KIS on Aug. 22; Delivery to Tyuratam in September
7L (No. 232) Delivery to Tyuratam in October
8L (No. 233) (manned) A mockup to be completed by Sept. 20; Delivery to Tyuratam in November or December


Final preparations

Mishin landed at the Tyuratam launch site on Sept. 13, 1967, at 15:10 Moscow Time for the first time since the disastrous mission of Soyuz-1 the previous April. In less than an hour, he already was at the processing facility at Site 31, where Vehicle 7K No. 4L was undergoing final preparations for launch. Although most problems had now been resolved, the next day, the personnel apparently had to deal with some depressurization in the spacecraft.

On September 17, Vehicle No. 4L was transported to another processing building for integration with the launch vehicle.

In parallel with the work on the L1 project, TsKBEM engineers had to deal with a multitude of other projects in Tyuratam, first of all, various issues with the massive infrastructure development for the L3 project and ongoing processing of Soyuz 7K-OK No. 5 and No. 6 spacecraft for an upcoming unmanned joint mission.

September 19: State Commission clears No. 4L for flight

The State Commission overseeing the launch of Vehicle No. 4 convened on Sept. 19, 1967, at 15:00. A leading test specialist Viktor Melnikov reported that the entire launch campaign had taken 71 days with an eight-hours-a-day and six-days-a-week work schedule.

As of September 19, a total of 12 issues had been reported during the pre-launch processing, eight of which were already closed and four were declared acceptable for the flight.

The preparation of the Vehicle No. 4L took 890 hours (around 37 days), including 240 hours of delays (10 days).

The launch was then scheduled for Sept. 26, 1967, around 03:00 Moscow Time. There were still some issues remaining with ground control, but the spacecraft was declared ready for the mission following the two dress rehearsals for flight controllers planned for September 22 and 24.

To track the mission during the flight over the Western Hemisphere, the Vladimir Komarov floating command and control ship was stationed in the port of Havana, Cuba.

Somewhat prophetically, Viktor Radutny, a propulsion specialist, reported about the low production quality of the 11D43 (RD-253) engine at Plant No. 19. The engine, which propelled the first stage of the UR-500K rocket, was given reliability of 0.992, compared to 0.9975 reliability calculated for the propulsion systems of the second and third stages of the rocket.

September 20: Launch delay

On September 20, Mishin apparently asked Shabarov whether the launch could take place on Sept. 26, 1967, despite problems with narrow-angle antennas, which could require a delay until September 28. He also contacted his deputy Igor Yurasov about the replacement of the fairing on the parachute container.

By September 22, the liftoff of Vehicle No. 4L was set for Sept. 28, 1967, at 01:11:54.44 Moscow Time.

Flight program

The flight program of the 7K-L1 Vehicle No. 4 called for a single orbit around the Earth followed by the firing of the Block D's engine for an injection into a lunar flyby trajectory. The vehicle would then travel around the Moon and return back to Earth.

The landing was probably planned at sea, because on Sept. 4, 1967, Mishin wrote a note about his discussion with G.I. Degtyarenko about the clarification of landing sites with the Soviet Navy, apparently in reaction to an earlier phone call on the same topic from a Navy officer named Dmitriev.

On the launch pad

On Sept. 26, 1967, at 16:30, the State Commission convened to review the readiness of Vehicle No. 4L, which was already on the launch pad at the time, presumably rolled out there around September 22.

According to Mishin's notes at the meeting, one of the fueling trucks was apparently late to arrive at the launch pad for propellant-loading operations and four other issues had to be dealt with during the final countdown. He also quoted S. Arkadeevich Krutovskikh as reporting that a two-channel central computer onboard the Block D upper stage was operating at 0.992 capacity. Also, Pikovsky reported that a transmitter operating at a meter frequency range had failed and would not be available during the flight.

The fourth L1 spacecraft fails at launch

The fourth launch of the L1 project took place during the night from Sept. 27 to Sept. 28, 1967. An UR-500K rocket lifted off from "Left" pad at Site 81 at 01:12 Moscow Time. However, at liftoff, the vehicle was already visibly crippled with only five of six RD-253 engines on the first stage firing. According to witnesses, the problem was apparent, as the rocket was wiggling and shaking, but continued climbing, because the engine shutoff command had been blocked in its flight control system for the first 50 seconds of the mission to ensure that it cleared the launch facility. (400)

The rocket then lost stability at T+61 seconds in flight and soon began disintegrating. (466) Its flaming debris finally fell between 40 and 50 kilometers from the launch site. (400)

As the rocket was failing, the newly designed Emergency Escape System, SAS, at the top of the L1 spacecraft was successfully activated. However due to unexpectedly high dynamic pressure on the vehicle during the separation from the rocket, the descent control system, SUS, failed to properly stabilize the descent module. As a result, the capsule landed in the direct vicinity of the crashed rocket. The rescue team, which arrived to recover the module witnessed a bizarre scene with the descent module sitting on the top of a small hill backdropped by a giant brown-yellowish cloud extending from horizon to horizon over the crash site.

The situation vividly illustrated the dangers of recovering the vehicle after a failure early in flight and required the project managers to look again at the safety of the personnel involved in such operations. (52)

Mishin returned back to Moscow from Tyuratam on Sept. 30, 1967, two days after the failed launch. The post-failure investigation revealed that a small rubber cover accidentally left in the engine line and ingested into the propellant line during the launch, had been the culprit in the launch failure. (466)

Read much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:


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The article and illustration by Anatoly Zak; Last update: October 24, 2020

Page editor: Alain Chabot, Last edit: September 28, 2017

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A night launch of an UR-500K rocket with a 7K-L1 spacecraft. Credit: RKK Energia