Zond-8 flies last mission of the L1 project
In October 1970, the Soviet L1 spacecraft looped behind the Moon for one last time, but still did not carry any cosmonauts onboard as originally intended. Although the final mission was announced as Zond-8 in accordance with the public nomenclature of the L1 project, behind the scenes, the official goal of the launch was switched from preparing the piloted circumlunar flight to gaining experience necessary for expeditions to the lunar surface.
The Zond-8 mission at a glance:
Preparations for flight
After the successful completion of the Zond-7 flight in August 1969, the working schedule called for another launch of the L1 test vehicle without crew by the end of the same year and a piloted flight around the Moon as early as April 1970. However, these plans had to be changed as the reverberating aftermath of the Apollo lunar landings had erased all the political rational for the L1 project in the eyes of Kremlin officials.
A critical meeting chaired by Sergei Afanasiev, Head of the General Machine-Building Ministry, convened on December 6, 1969, at the TsKBEM design bureau, (the prime developer of piloted vehicles) to review the status of the program. The majority of officials at the gathering voted down the idea of flying crews aboard the L1 ships. However, the engineers were cleared to press on with the L3 project intended to put a cosmonaut on the lunar surface, which still had political support in 1970 (78), despite continuing budget shortfall. (774)
Under these circumstances, one of three largely completed vehicles from the original L1 series -- No. 14L -- was formally re-purposed for the benefit of the L3 project. (52) Around the same time, the scientific community tabled a proposal for forming a large experimental radio interferometer in space using a converted L1 ship. (78) Remaining L1 ships No. 15 and No. 16 could probably be used for that purpose, but the project never materialized.
By the end of January 1970, Vehicle No. 14 was already delivered to the launch site and ready for flight, but political issues apparently kept it on the ground for much of the year. By the time it reached the launch pad in October 1970, it was apparently already marked as the last of its kind. (142)
The flight profile of the final L1 launch still emulated previous L1 missions. One major difference in the flight scenario was the return trajectory, which would take the vehicle over the North Pole of the Earth, rather than the South Pole as in the previous missions.
The northern trajectory provided more communications coverage for the Soviet ground stations during the final phase of the flight and, apparently, did not require a dual reentry into the atmosphere with a short "skip" back into space to reach the landing site.
However, the northern trajectory would overshoot the Soviet territory, instead concluding with a splashdown in the Indian Ocean, which was opposed by Air Force officials, according to the influential head of the cosmonaut training General Kamanin. The Air Force obviously felt more comfortable organizing recovery operations inside the familiar Soviet landmass rather than over the treacherous waters of the Indian Ocean, which required heavy involvement from the Navy. (142)
Mishin apparently argued that the northern path will provide some fuel savings (probably because the capsule would have a shorter period of time to maintain its attitude control during a single atmospheric entry). In combination with the aerodynamic control during the descent, future lunar expeditions could achieve more accurate water landings, thus facilitating search and rescue operations at sea. Over the objections of the Air Force, on January 15, 1970, Vasily Mishin, Head of TsKBEM, assigned his top ballistics experts Refat Appazov and Vitaly Bezverby to design a trajectory which would put the spacecraft over the Yamal Peninsula and the Dikson Bay to splash down in the Indian Ocean. (774)
Zond-8 lifts off
Three booster stages and a single firing of the fourth (Block D) stage successfully delivered the L1/Block D stack into an initial parking orbit. After a single loop around the Earth, Block D fired again sending the spacecraft into deep space. The Soviet authorities announced the mission as Zond-8.
A day after launch, as the spacecraft was moving away from Earth, it photographed its home planet from a distance of 64,480 kilometers.
On October 22, the ship conducted a trajectory correction maneuver at a distance of 250,000 kilometers from Earth, which ensured its flyby of the Moon.
On October 24, Zond-8 looped around the Moon at a minimum distance of 1,120 kilometers from its surface. As in the previous mission, the ship completed two photo sessions picturing the Earth and the Moon and also managed to capture an iconic but already familiar scene of the earthrise over the rugged curved horizon of the Moon.
Zond-8 returns to Earth
In September 1970, in anticipation of the Zond-8 return to Earth, (set for October 27, 1970), the Soviet Black Sea fleet received the assignment to deploy in the Indian Ocean. Commanded by Counter-admiral A.A. Trofimov, the flotilla counted at least nine ships, including KU S. Chelyuskin, EOS Dikson, Baskunchak, S. Dezhnev, Donbass, Taman, EM Vozbuzhdenniy, BDK-13, TN Grodno. The vessels were also supported by Tu-95RTs long-range strategic bombers from the Northern Fleet. According to the plan, the ships had to deliver the Descent Module to the port of Bombay, India, to later than six hours after its splashdown.
By noon on October 20, the day of the launch, the search ships had already deployed at their pre-determined positions spread along the final descent trajectory of the Zond-8 mission.
However, at 15:37 Moscow Time on October 27, as the spacecraft was hurtling toward Earth along its north-to-south trajectory around an hour before the reentry, the Central Command Post of the Navy issued the fleet new deployment coordinates located further north. Apparently, a failure of the solar attitude control sensor aboard Zond-8 made it impossible to orient the capsule so that it could generate aerodynamic lift during reentry and avoid a steeper ballistic descent. As a result, the projected landing zone shifted further north resulting from the shorter reentry profile. (874)
Because the chance of the ballistic descent had always been factored into the positioning of search and rescue assets, at least one of the ships involved into the Zond-8 recovery operations have been in the area from the outset, even when the majority of the force was deployed near the primary landing zone.
In any case, the Zond-8 recovery operations seemingly went without a hitch. The plasma trail of the reentering spacecraft was first spotted from the ships speeding toward the new landing area at 16:39 Moscow Time and, six minutes later, the radio-tracking became possible. All ships were reportedly tracking the Descent Module through radio signals.
The capsule splashed down in the Indian Ocean at 16:55 Moscow Time around 730 kilometers south-east of the Chagos Archipelago. The exact landing coordinates were 10 degrees 22 minutes North latitude and 76 degrees 57 minutes East longitude. (774)
Despite the last-minute change of the landing zone, the capsule was reported to be 24 kilometers from the (newly) projected landing point and just 12 kilometers from the nearest recovery ship -- the Taman oceanographic vessel. An operator of the radio-locator station on the Taman detected the capsule on the water surface at 17:02 Moscow Time and slightly more than an hour later, the vessel reached the Descent Module. At 18:15 Moscow Time, the capsule was already hoisted onto the deck of the recovery ship. (774) According to Soviet Navy veterans, entire recovery operation took 1 hour and 26 minutes. (927)
Post-flight inspection of the Descent Module showed that the photo-camera aboard Zond-8 used up its entire load of film, producing nearly 200 high-quality images of the Earth and the Moon. The photographic materials from the mission were later analyzed at the Department of the Moon and planets, led by Yu. N. Lipskiy, at the Shternberg State Astronomy Institute, GAI. (874)
However, despite the successful completion of the Zond-8 flight and the two previous missions, the overall safety margins of the UR-500K-L1 system were deemed inadequate for carrying cosmonauts around the Moon, in addition to the fact that the project had lost its propaganda value after the American lunar landing. By the time the Zond-8 returned to Earth, all the cosmonauts originally training for flying the L1 vehicles around the Moon had already been re-assigned to other projects. (231)
A view of the Moon from Zond-8. Credit: Roskosmos
A view of the earthrise over the Moon from Zond-8. Credit: Roskosmos
A Descent Module of the L1 spacecraft is being recovered from the ocean. Credit: Roskosmos
The Descent Module of the Zond-8 spacecraft on the deck of the Taman' search and rescue ship after landing. Credit: Roskosmos
Soviet-era poster dedicated to the Zond-8 mission. Credit: Roskosmos