L1 No. 7L: A circumlunar mission attempt
On April 23, 1968, at the height of the Moon Race, the USSR made a secret attempt to fly unmanned circumlunar vehicle L1 No. 7L behind the Moon with the goal of sending a crew along the same path as early as October 1968.
The 7K-L1 No. 7 mission at a glance:
Following a standard flight scenario, the UR-500K rocket was programmed to deliver the 7K-L1 No. 7 spacecraft into an initial parking orbit 589 seconds (9.8 minutes) after liftoff. (466) The second firing of the Block-D upper stage would then insert the spacecraft onto a near-lunar trajectory to simulate the future manned mission behind the Moon.
The only uncertainty complicating the final planning for the launch of Vehicle No. 7 remained around the landing.
The primary flight goal for the L1 No. 7 vehicle was apparently the so-called skip entry, which would use the aerodynamic lift of the Descent Module to briefly exit the Earth's atmosphere on the return path and thus allow the capsule to reach the Soviet territory during the second entry. However, without a properly maintained attitude of the module enabling the aerodynamic lift, it could end up on a much steeper, purely ballistic trajectory ending in the Indian Ocean or even in the Pacific.
As before, the head of cosmonaut training Nikolai Kamanin pledged to fight the so-far prevailing policy of blowing up the Descent Module of the L1 spacecraft, if it failed to reach the Soviet territory. In his opposition, Kamanin was apparently motivated by the desire to give search and rescue teams, especially Navy crews with little experience and no adequate equipment for tracking spacecraft, an opportunity to practice recovery operations. Obviously, the Soviet cosmonauts involved into the effort shared that opinion. In his records, Kamanin also expressed the need for a separate Navy training exercise in the Black Sea and in the Indian Ocean to practice the support for the L1 project.
As early as February 1968, Mishin requested from seven to nine ships to be deployed in the Indian Ocean. With some reluctance, the Soviet Navy apparently agreed to mount the complex recovery operation which would cost more than 100 million rubles.
Soon thereafter, on April 1, Mishin discussed with his colleagues Konstantin Bushuev, Yakov Tregub and Georgy Degtyarenko the option of disabling the self-destruct system, APO, aboard Vehicle No. 7, in case of its ballistic return. (774)
Preparations for flight
The factory assembly of Vehicle No. 7L was declared completed on April 10, 1967, and exactly a month later, it began testing at Checkout and Testing Station, KIS, at the TsKBEM design bureau in Podlipki near Moscow. The electric tests were completed on July 2, followed by final checks on July 16, 1967. A number of problems had to be corrected in the operation of the vehicle's new onboard computer Argon-11, known in Russian as "Spetsvychislitel," or SV for short. (662) The failure of one channel in the SV computer required its full replacement taking around 200 hours of extra work.
Integrated tests of the spacecraft also revealed that some components had poor protection from interference. (774)
As of August 1967, the launch of Vehicle No. 7L was planned for October of the same year, but the spacecraft did not make it to the Tyuratam launch site until around February 1968, as a result of the domino effect of delays with previous missions. (466)
The final preparations for launch of Vehicle No. 7L in March and April 1968 was taking place almost in parallel with the work on a pair of Soyuz 7K-OK spacecraft which had lifted off just a week earlier, so many officials and engineering personnel participated in both launch campaigns.
The final assembly of Vehicle No. 7 began on April 10, 1968, with the integration of the Emergency Escape Rocket, SAS. The next day (April 11), the technical management reviewed the readiness of the vehicle for flight. Lt. Colonel V. P. Zhuravlev, who led the processing team, reported on a number of recently resolved issues, including the crash of Channel B in the replacement SV computer, which could be successfully rebooted; the replacement of SNT-11 and Krechet instruments; an interruption in the telemetry channel in one of the antennas and the loss of pressure in the KA-1 and KA-2 propulsion system lines due to excessive pressure. The total processing time reached 648 hours, including 48 hours of delays. Arkady Ostashev reported that a number of upgrades also had to be made at the launch site, but the vehicle had been fully assembled and tested and had no unresolved issues.
According to the processing schedule on April 11, the fueling of the Block D and its SOZ stabilization thrusters with hypergolic propellants was to be completed by 17:00 Moscow Time and, in the next four hours, it would be prepared for transfer to the integration hall. The vehicle was to be ready for integration with the L1 spacecraft by the morning of April 12.
As planned, the payload section with the 7K-1L spacecraft also arrived at the integration facility on the morning of April 12, 1968, but in a bizarre incident, a wrench was discovered in the hatch of the fueling line. Mishin immediately issued an order to the technical head of the L1 project Yuri Semenov to update the inspection procedures.
The State Commission met at 11:00 Moscow Time on April 13 to review the status of Vehicle No. 7. General Aleksandr Kurushin, the Chief of the Tyuratam launch site, chaired the event.
By April 19, the final preparations were proceeding according to the schedule which even had a built-in "backup" day on April 21 to resolve possible unforeseen problems. The weather was unusually cold and windy in Tyuratam, with temperatures plunging to minus 5C degrees.
On April 19, Vladimir Chelomei and his associates from the TsKBM design bureau, which developed the UR-500K rocket series, arrived at Tyuratam. They were followed by the head of TsKBEM Vasily Mishin, who returned from Crimea, where he had monitored the just completed dual flight of the Soyuz 7K-OK spacecraft. (820)
On April 22, around 16:30 Moscow Time, the State Commission had a formal meeting, where Mishin and Chelomei announced that the L1 spacecraft was ready for launch. The officials gave the green light to the liftoff the next day at 02:01:27 Moscow Time. According to Kamanin, the last item on the agenda of the meeting was Mishin's "proposal" to activate the self-destruct mechanism aboard the reentry vehicle, unless it successfully entered a controlled (aerodynamic) descent. Mishin's deputy Evgeny Shabarov supported that idea. Other key officials, including Chelomei, Kurushin, Kirillov and Gurovsky preferred not to get involved into the controversy, however, Lobov, Kazakov, N. N. Yuryshev and Vladimir Barmin apparently sided with Kamanin, who argued for disabling the self-destruct system.
Kamanin wrote sarcastically that the official reasoning for the measure was to prevent "secret" Soviet radio-electronics from falling into American hands. During the meeting, Kamanin brought the argument that due to the high probability of ballistic return during future manned flights, the L1 project would need at least one unmanned mission to actually demonstrate all aspects of such a landing and the associated recovery operations. Kamanin also questioned the wisdom of deploying a fleet of Soviet vessels in the Indian Ocean, if they had no chance for actual recovery. According to Kamanin, Mishin then said that he himself had been against any ocean landings, but was countered by a Navy representative Dmitriev, who responded that Mishin had previously declined to sign a waiver allowing the Navy not to deploy during this mission. Georgy Tyulin, who chaired the commission, apparently expressed his disagreement with Mishin's arguments three times, but, ultimately, the group decided to hold a separate meeting on the matter. (820) However, in his own notes about the same event, Mishin listed the "re-configuration" of the APO self-destruct mechanism, among other last minute tasks.
According to the final processing schedule, the military personnel was scheduled to line up at Site 81 between 18:00 and 18:30 Moscow Time and then take operational positions from 20:10 to 22:15. The cryogenic liquid oxygen would then be loaded into the oxidizer tank of the Block D upper stage from 20:55 to 22:15. (774)
Around an hour after midnight on April 23, 1968, cosmonauts and Air Force officials headed to Site 130, located around 10 kilometers west of UR-500K launch pad, while Kamanin and General Karpov went to a command bunker at Site 82 located just south of the pad. It was a cool, dark and starry night. (820)
The sixth L1 spacecraft lifts off
A UR-500K/Block D rocket carrying the L1 No. 7L spacecraft lifted off exactly as scheduled on April 23, 1968, at 02:01:27.29 Moscow Time from the "Right" pad at Site 81 in Tyuratam. It was the 10th mission for the UR-500 series. The powered ascent proceeded seemingly well until the separation of the payload fairing at T+194.64 seconds and the emergency cutoff of the second stage. According to Kamanin, the flame of the rocket disappeared around 260 seconds into the flight, even though he estimated, it was supposed to operate for another 79 seconds. It was clear, that the mission had failed and Kamanin immediately called General Dolgushin and directed him to dispatch search aircraft to the area of Dzhezkazgan. Kamanin then headed to Site 2 to further coordinate the situation.
At 02:50 Moscow Time, it was confirmed that the Emergency Escape System had been activated and the Descent Module had touched down 520 kilometers east of the launch site or 110 kilometers from Dzhezkazgan.
Ground controllers continued receiving telemetry until T+357 seconds and the landing site was determined by the signals from the Krug navigation system and with the help of ballistic estimates. Dolgushin also told Kamanin that two Il-14 aircraft and one Mi-4 helicopter were in the landing area but had not yet picked up its signals. A few minutes later, a helicopter captain radioed: "the spacecraft located, it is on fire." Officials immediately doubted the report, because the capsule could be easily confused with the second or third stage of the rocket and expected to crash in the same general area. Still, General Kutasin also confirmed that the spacecraft was on fire. The real situation became clear only in the morning, around an hour after dawn, when, indeed, it was confirmed that the Descent Module had landed without problems and all its systems operated well for the exception of the Priboy transmitter.
At 07:30 Georgy Tyulin called Mishin and confirmed that the Descent Module had been found.
By 15:00, a Mi-6 helicopter delivered the capsule to Dzhezkazgan, from where it was to be shipped to Moscow aboard an An-12 transport aircraft the next morning.
In the meantime, space officials formed an accident investigation commission led by Mishin and Chelomei. Kamanin delegated Colonel Vashenko to represent the Air Force in the group. It was clear that, while the rocket was operating as planned, the "emergency" command had been issued aboard the spacecraft, prompting the activation of the emergency engine cutoff on the second stage.
At 16:00 Moscow Time, the commission reviewed the preliminary information and most officials already agreed that some kind of electrical problem onboard the spacecraft had caused the accident. (820)
Perhaps remembering pre-launch troubles, there were also some early doubts in the operation of the SV flight control computer, whose channels B and V signaled a reboot at T+86 seconds in flight. However, during the day, Shabarov, Kirilov, Ostashev and Kirilyuk all confirmed to Mishin that the computer had operated as planned and that the interruption in its work had been caused by external reasons. (774)
When the State Commission gathered for a formal meeting, Vladilen Finogeev, who had led the development of the flight control computer, outlined the events based on the preliminary review of the available telemetry. Some indications of problems with the electric system and the telemetry system were revealed even before liftoff. Then, at T+85.5 seconds, an electric charge was detected on the body of the vehicle, but it disappeared after the separation of the descent module, simply because the telemetry had been flowing via the Block D stage (which remained attached to the rocket). At the same moment, the two channels of the SV computer quit and the output voltage on the PTS-1000 current converter unit fell below 34 volts (instead of the required 40 volts). As a result, the flight control system could no longer function normally. The electric current in the power supply system of the Descent Module remained at the maximum level and fluctuated between 7 and 10 amperes. There were also anomalies in the data of the IP-33 telemetry sensors. Finally, the Current Measurement System, SIT, also misbehaved, indicating some damage shortly before or right after the liftoff and escalating from there.
Evgeny Shabarov concluded that it was too early to hypothesize about the culprit and some additional analysis would be needed. He also proposed a re-test of Vehicle No. 8 by the personnel of the Checkout and Control Station, KIS, in Podlipki.
In the evening of April 23, Mishin and the top managers departed Tyuratam for Moscow.
Investigation completed into the Vehicle No. 7 accident
On April 24, Mishin directed the formation of four technical groups to further investigate the mystery that had caused the accident with Vehicle No. 7:
Evgeny Shabarov was assigned the overall management of the investigation efforts and the head of TsKBEM's production facility Konstantin Vachnadze was asked to supervise testing at KIS.
The heads of groups made their presentations to Mishin at 15:10 Moscow Time on April 25, 1968.
It turned out that the flight of Vehicle No. 7 had been terminated by a failure command from the Autonomous Control System, SAU. In turn, the faulty command had been triggered by stray electricity on the body of the vehicle from a power supply converter.
The investigation concluded that the culprit was in a design flaw missed by TsKBEM's Department No. 212 led by Andrei Reshetin. The team had apparently made improper installation of the three-axis gyro stabilization platform, TGS, inside the Descent Module. (52)
It is clear from Mishin's notes that the investigation into the accident with Vehicle No. 7L continued for at least three weeks. On May 16, 1968, he mentioned in his records the preparation for the collegium meeting on the subject, where his deputy Shabarov was apparently scheduled to present the conclusion of the expert commission on the accident.
On May 28, 1968, another technical meeting on the 7K-OK and L1 projects took place. The key topic of discussion was how to send a crew on a circumlunar mission before October of that year. (774)
Members of the accident commission for the 7K-L1 No. 7L mission:
Read much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:
Evgeny Shabarov, deputy to Vasily Mishin, led preparations for the launch of L1 No. 7L vehicle.
The flight control specialist Vladilen Finogeev was one of the leading figures in the commission investigating L1 No. 7L launch accident. Credit: NPTs AP
G. A. Kirilyuk oversaw the installation of the VS computer on the L1 No. 7L spacecraft. Credit: NPTs AP
Andrei Reshetin led Department 212 at TsKBEM responsible for the design of the L1 descent module. Credit: RKK Energia