Authors note: an obsolete article, showing the status of Western understanding of the Soyuz project ca. 1987.
The workhorse of Soviet manned spaceflight has been the Soyuz spacecraft, which has reliably taken cosmonauts into space for over thirty years. Versions have been developed for a wide variety of missions - earth orbit science, circumlunar, lunar orbital, military interceptors, light space stations, free-flying man-tended laboratories, space station manned ferries, space station logistics vehicles. While the basic structure of the spacecraft remains the same, the internal systems have been markedly different. This remarkable spacecraft has been launched in greater numbers than any other in history. It is to continue in service as the Russian ferry for the International Space Station well into the next century.
Beginnings: Design and Development, 1961-1966
On May 25, 1961 President Kennedy proposed that the United States land an American on the moon by the end of that decade. Six months and three days later the prime contractor was chosen. Major subcontractors were chosen in January 1962 and it was obvious that the Americans were in dead earnest.
Studies were begun almost immediately in the Soviet Union to meet the American challenge. The technical proposals of the American competitors in the Apollo program were studied. Sergei Korolev, the Soviet chief designer, initially proposed a modification of Russia's first manned spacecraft, "Vostok Zh", for earth orbit rendezvous and translunar missions. But another study, using a spacecraft already on the Korolev OKB's drawing boards with similarities to General Electric's proposed Apollo design, was more attractive. It was called Soyuz, and used a series of five launches by the existing SL-4 booster of engine, fuel, and spacecraft modules to form a 19 tonne circumlunar complex in low earth orbit. The main engine would then fire, sending cosmonauts on a loop around the moon. The Vostok design was dropped (its pure ballistic reentry vehicle would impose crushing G loads on return from a circumlunar mission).
Korolev's OKB continued studies and hardware tests on the multi-launch approach. However the Chelomei design bureau, in favor with Khrushchev, was already developing the much larger Proton booster in parallel. This would be used in a single launch to send Chelomei's LK-1 one or two man capsule on a loop around the moon. After the death of Khruschev, Chelomei's patron, a revised decision was made to accomplish the circumlunar mission with a single launch of a lightened Soyuz (designated "L1") atop a Proton booster for a loop around the moon. A two-skip reentry would be used to return the spacecraft to earth. This entailed a dip into the atmosphere over the South Pole, slowing the Soyuz descent module's velocity from 11 km/sec to less than 7.8 km/sec. The Soyuz would then use its body lift to skip out into space, finally reentering again and coming to a landing within the territory of the Soviet Union. It was expected that this could be accomplished by November 1967, beating the U.S. plans for such a mission.
The lunar landing mission itself was a bigger challenge. The Russians faced the same technical choices as the Americans. They chose an austere version of the Americans' lunar orbit rendezvous method. This would involve launch of a Soyuz spacecraft ("LOK") with a lunar terminal descent/ascent stage ("Block D/LK") atop the enormous new "N" launch vehicle. The entire assembly would then be fired into a translunar trajectory. Using a variant of the lunar orbit rendezvous method known as the "lunar crasher", a single stage ("Block D") would brake the LOK/LK spacecraft into lunar orbit. A single cosmonaut from the two-man crew would spacewalk from the Soyuz LOK back to the LK lander. The lander would descend towards the moon using the Block D stage. This would be jettisoned after doing most of the work of braking to the lunar surface. The LK would then hover to a final landing on the surface. After surface exploration, the cosmonaut would reenter the LK, which would launch itself into lunar orbit for rendezvous and docking with the waiting LOK. The cosmonaut would again transfer to the LOK, and the LOK's engine would fire for the return to earth.
While the American program had its share of setbacks, the Soviet program experienced major failures and delays in all areas. They started late, in reaction to the American program, instead of being first out of the blocks. The Soviet Union had a major leadership change with Khrushchev's ouster in 1965, while Lyndon Johnson saw the Apollo program through from its inception to within months of the lunar landing. Sergei Korolev, the Russian chief designer, died just months before the first test flight of the Soyuz. The series of failures and disasters that followed can be partly attributed to the lack of his firm hand to guide the program. The higher priority SS-9 and SS-11 ICBM programs commanded the attention and talent of the same design bureaus that were working on the moon program. Acrimony between the Chelomei and Korolev design bureaus was constant, with the shifting leadership in the Kremlin adding fuel to the fire. Glushko, leader of the prime rocket engine design bureau, refused to work with Korolev due to a dispute over which propellants should be used in the new N vehicle. Glushko favored storable liquid propellants. These were expensive and toxic, but provided operational advantages and were common with the military engines that were his highest priority. Korolev insisted on liquid oxygen and kerosene, utilized in large clusters to obtain plug-nozzle performance. In the end, Korolev was forced to turn to the Kuznetsov turbine engine bureau to design his engines. Kuznetsov had no production experience in rocket engines. The engines would be the undoing of the booster and the program.
The Soyuz as developed followed closely the 1962-64 design studies. While the chosen American Apollo design took as its first assumption that the return capsule would weigh five tonnes for three men, the Soyuz design cut this to three tonnes. This was accomplished by putting all systems not necessary for reentry and recovery into either the service module or orbital module. The orbital module provided additional living space for the cosmonauts, an airlock, the docking equipment, and storage of cargo. It would also serve as the basis for the cabin of the LK lander. The descent module provided seats for a crew of three, recovery parachutes and rockets, heat shield, basic environmental control equipment, consumables for the lunar return flight, and ship's controls. It used aerodynamic lift during reentry to reduce G loads on the crew and fly to a designated recovery area. The service module provided in-orbit systems such as electrical power (by batteries or solar cells), propulsion, attitude control, and other equipment not necessary for reentry. Together, the Soyuz descent and orbital modules provided the same functions as the Apollo command module, while offering an airlock, more volume, and weighing 1,500 kg less.
The systems of the Soyuz reflected Soviet technology at the time of its design. The general level was that of the American Mercury spacecraft. Attitude control was provided by hydrogen peroxide thrusters. Attitude determination was by horizon and ion flow sensors, with the gyro platform only spun up prior to maneuvers. Automatic control was by analog sequencer systems, with maneuvers calculated by ground control. The American Gemini and Apollo would introduce multipropellant attitude control, integral with propulsion; full-time attitude determination and inertial guidance; and control by on-board digital computers. Soyuz would not see these improvements for fifteen years.
However the Soyuz system worked and obtained reliability through its very simplicity. Further, it provided for automatic, unmanned rendezvous and docking, something no one else has demonstrated to this day. It got the job done with significantly less payload than the American Apollo. Indeed, the Zond version, with reduced fuel and no orbital module, accomplished the circumlunar version with the total spacecraft weighing less than the Apollo command module alone! Although he died before the first flight, Sergei Korolev left a final legacy to Soviet spaceflight of lasting importance.
Initial Flight Test and The Lunar Program, 1966-1969
Engineering flight tests of the lower stages of the Proton booster in 1965 and 1966 were successful. Unmanned flight tests of the Soyuz L-1 spacecraft in November 1966 and February 1967 were partially successful (both experienced problems with the heat shield and descent parachute). Two flights of the Proton booster, in March and April 1967, seem to have tested the Soyuz reentry capsule at lunar reentry speeds. The Apollo fire in January had killed three American astronauts and set the U.S. program back at least eighteen months. The ambitious combined missions of Soyuz 1/2 scheduled for April would demonstrate, in earth orbit, all elements of the lunar orbit portion of the Soyuz mission: rendezvous, docking, and extra vehicular activity. This was almost eighteen months ahead of plans for a similar American mission. By the third week of April in 1967 the Russian team must have felt themselves well on the way to winning the moon race. Then came the stunning blow: multiple failures aboard Soyuz 1 culminating in the death of Vladimir Komarov. The Soyuz 2 crew stood down, and the Soyuz spacecraft went into a major redesign.
Meanwhile tests continued of other systems. The twin flights of Kosmos 186/188 and Kosmos 212/213 in October 1967 and April 1968 proved the automatic rendezvous and docking systems. However the next test of the translunar Proton in November 1967 failed to reach orbit. It was the beginning of a nightmarish series of problems with the Proton. Zond 4 in March 1968, the first test in deep space, was only partially successful-the Soyuz descent module was not recovered. Another failure in April to reach orbit evidently either exhausted the available stock of Proton launch vehicles or led to some minor redesign. There was a five month hiatus in Proton launches.
In the fall of 1968 the momentum accelerated; the moon race was back on. The redesigned Soyuz was tested in an unmanned flight in August. Zond 5 in September looped around the moon and verified all portions of the L-1 circumlunar mission except the two-skip reentry. In October Soyuz 2 (unmanned) and 3 (manned) were orbited, rendezvoused, but failed to dock. However safety of the new design was proven. Meanwhile, the Americans successfully launched the redesigned Apollo the same month and announced that they would consider attempting a translunar flight on the next mission.
Zond 6 in November proved the two-skip reentry technique and the way seemed clear for a Zond manned circumlunar mission on December 9, 1968. The prime crewman, Pavel Belyayev, and his backup, Valeri Bykovsky, reported to Baikonur Cosmodrome for the flight. However that month's launch window came and went without a launch attempt. Apollo 8 orbited the moon at the end of the month. The propaganda value being gone, no manned Zond circumlunar flight was ever made (two more unmanned tests were made in 1969 and 1970 with surplus hardware). Belyayev developed a severe stomach ulcer, and died of complications a year later. Bykovsky, who was also the commander for the cancelled Soyuz 2 mission, went into disgrace and did not fly again until 1976. Nikolai Kamenin, the GRU commander of the cosmonaut detachment, and the rest of the management responsible for the debacle continued in their positions.
Soyuz 4 and 5 finally accomplished the original Soyuz 1/2 mission in January 1969. The two manned craft docked and two crewmembers transferred by EVA. But the dazzling success of flight after flight of the Apollo program meant the loss of the moon race.
By July the triumph of Apollo 11 made further Soviet effort futile. The development of the lunar lander was over a year behind schedule, with tests in earth orbit finally accomplished in 1970-1971. The N launch vehicle was also dogged by difficulties. First rolled out in late 1968, its first launch in February 1969 resulted in explosion of the vehicle 70 seconds after liftoff. It blew up on the pad on the next launch attempt in July 1969, ending any chance of beating America to a moon landing. Following extensive ground tests and redesign, further launch attempts in July 1971 and November 1972 exploded prior to second stage ignition. Further work was abandoned as Glushko assumed control of the Korolev bureau in April 1974.
An unmanned series of Luna spacecraft returned lunar soil to the earth in the early seventies and allowed Soviet propaganda instruments to issue the incredible deception that Russia had never intended to put men on the moon. However, the cover-up weakened over the years. The Zond manned circumlunar program was well documented in cosmonaut's memoirs by the mid-1980's. The lunar landing mission was finally admitted and details published in 1990.
The Soyuz Ferry Program (1969-1987)
The Salyut space station was born in the debris of the moon program. Preliminary design work may have been undertaken on Salyut in the context of the lunar program. Again, Chelomei, with an ongoing military space station project underway, the Almaz, was pushed aside. The Salyut design, using the hull of the Almaz, but equipped with Soyuz systems, could have served either as an initial earth space station launched by the Proton booster, or a lunar orbiting way station launched by the N vehicle. As authorized in January 1969, the Salyut space station would utilize a modification of the Soyuz with a lighter docking/transfer system as a ferry craft. While the Salyut program has had its share of failures and setbacks, its measured and evolutionary approach finally enabled the Soviets to achieve the consistent success their space program had enjoyed prior to the death of Sergei Korolev.
To use up existing lunar Soyuz assets and to keep their hand in, four "bridging" flights were flown in 1969 and 1970 (Soyuz 6-9). These proved multivehicle control techniques, long-duration spaceflight, and prototype space welding equipment.
The launch of Salyut 1 in 1971 was successful. The first Soyuz 10 ferry experienced a failure with its docking equipment. The backup successfully docked and the Russian people ecstatically greeted the proof that the Russians still led some aspects of manned spaceflight. Then, tragedy again struck. An open cabin valve led to decompression of the descent module during return to earth, killing the crew. The Soviet Union went into deep shock, and the Soyuz into a minor redesign.
Meanwhile, funded by the inertia of the Apollo program, and equipped with surplus boosters and spacecraft from the reduced moon program, America proceeded with their Skylab space station. The Russians were confident of keeping the lead. A flight test of the new Soyuz ferry in June 1972 was successful. But launch of the next Salyut in July failed. By spring of the next year it still seemed possible upstage the Americans. Two Salyuts, one "civilian" from the Korolev bureau and one "military" (Chelomei's Almaz), had been prepared. Salyut 2, the Almaz design, launched in April 1973, suffered a control failure and went into a fatal spin, tearing lose it solar panels and antennas. The civilian station reached orbit on May 11, but suffered an immediate control failure and never even received a Salyut designation. Skylab was launched three days later and America again took the lead in all aspects of spaceflight. Kamenin and other management responsible for the disasters of the previous five years were purged. GRU Colonel-Cosmonaut Vladimir Shatalov took command of the cosmonaut detachment.
The moon race and the station race were over; detente was the order of the day. All during the seventies, while the Americans abandoned space exploration as a national commitment, the Soviets proceeded with development of a whole constellation of orbiting space stations, ferry craft, cargo ships, and special purpose modules.
The backbone of this effort was the Soyuz ferry version. This was a Soyuz stripped of all equipment not required for the simple mission of docking with and returning from the Salyut. It used batteries, instead of solar panels for electrical power, which limited its duration to four days. At the same time, redesign of some systems provided an in-orbit storage duration of ninety days when docked to Salyut. Having learned a lesson from the Soyuz 11 tragedy, the crew wore full space suits, although this limited the craft to a crew of two. The third seat position was occupied by the environmental control system for the space suits. It also retained the Igla automatic rendezvous and docking system, although this was subject to detailed redesign during the series.
Detente led to a joint U.S.-Soviet Apollo-Soyuz flight for test purposes. When the technical details of the Soyuz were revealed publicly, the U.S. press had a field day. Forgetting the design's early-sixties origins, the press derided its lack of inertial navigation, digital computers, and systems redundancy. Much of this reflected differing engineering philosophies. The Russians have always sought reliability through simplicity. The Americans design much more complex (and expensive) systems to do the same job and have to obtain reliability through redundancy. The record shows that while the American approach provides them with more flexibility when things go wrong, the Russian approach gets the job done and provides equivalent reliability at lower cost.
The Soviets put a significant effort into the Apollo-Soyuz Test Program (ASTP), flying a total of six spacecraft to support the single docking with the Americans. The spacecraft was basically the Soyuz ferry, with all automatic docking systems deleted, solar cells in place of batteries, a universal docking system in place of the standard one, and minor ECS and radio modifications for compatibility with American systems. Soyuz 22 was the backup Soyuz ASTP with the East German MKF6 earth resources photo system in place of the docking collar. It was used for the last manned Soyuz independent mission during a hiatus in Salyut launches.
Salyut 3, the first military-dedicated space station, was finally launched in 1974. The Soyuz 14 ferry mission was successful. The second failed to dock, reportedly due to a failure of the new Progress-type automatic docking system, which made the ship uncontrollable close to the station. Salyut 5, a repeat military mission in 1976, was visited by two crews per original plan. The military Salyut series was then abandoned. The tests evidently did not prove the utility of dedicated man-tended reconnaissance platforms. The military instead developed two models of large Proton-launched unmanned platforms, which could be operated independently or docked with the Salyut station.
Meanwhile, the more public "civilian" Salyut program led to progressive development of the Salyut from the limited Salyut 4 (one docking port, limited endurance), through Salyut 6 and 7 (two docking ports, repairable, refuellable, unlimited endurance), through to Mir (space station core). To service these platforms, the Soyuz design went through concurrent improvement.
The first objective was to develop a craft for unmanned replenishment of the station. Salyut required fuel, to maintain its orbit against atmospheric drag; oxygen, water, and food for its crews; replacement equipment and spare parts; and new experiments. These averaged 300 kg of fuel and 400 kg of other supplies per month of operation. So a version of the Soyuz ferry was developed, called Progress. The descent module was replaced by fuel tanks with 975 kg of fuel for refueling of Salyut. The orbital module was retained, but filled with 1,320 kg of dry cargo, water, and air. Progress would automatically dock with Salyut, be unloaded by the crew, refuel the station, and use any of its own spare fuel to raise Salyut's orbit. Then the orbital module would be filled with trash, Progress would separate, and be commanded to a destructive reentry in the earth's atmosphere. For some unaccountable reason, the 49 Progress missions to mid-1991 have had a perfect mission success rate, while the Soyuz ferry's 38 missions alone suffered a launch, propulsion, or docking system failure 17% of the time.
So the Soyuz also required improvement. Reliability had to be increased. In-orbit storage of the Soyuz was limited to ninety days. This required numerous nonproductive visiting flights for which the only technical purpose was to swap spacecraft, leaving the long term crew with a "fresh" Soyuz. Technical advances since the early sixties meant that numerous systems could be reduced in weight, increased in flexibility. The result was a complete redesign, resulting in the Soyuz T.
While not often realized, Soyuz T had little in common with the earlier Soyuz except its structure. The service module was completely redone. An integrated reaction control system/main engine fuel system, using more efficient motors, greatly increased the ship's maneuverability. New lightweight solar cells provided long endurance. Detail redesign of all ship's systems doubled in-orbit storage time to six months. Digital computer systems replaced the analog "juke box" systems, leading to controls that showed only a whiff of their ancestry in the trusty earth position gage. Crew was again increased to three, all with spacesuits. The periscope was moved to the descent module centerline. The orbital module interior was modified to carry significant cargo for transport to Salyut, a lightweight launch escape system was introduced, improved docking systems were added. The Soyuz grew in weight by 50 kg, while payload increased by 400 kg - one additional crewmember and 200 kg of maneuver fuel. The result was a much more redundant and flexible spacecraft. The final model T built fully demonstrated this flexibility. Soyuz T-15 docked with the Mir station, undocked, rendezvoused and docked with the Salyut 7 station and then returned to Mir. Such maneuvering, endurance, and manual docking techniques were impossible with earlier designs.
With the introduction of Mir, the latest version, Soyuz TM appeared. This was essentially a Soyuz T, but with the new lighter Kurs rendezvous and docking system, further increased fuel load, and improved landing systems. Payload increased another 400 kg - 200 kg of cargo and another 200 kg of fuel. This version is able to approach, maneuver about, and dock with any port of another spacecraft, without that craft's cooperative maneuvering. Thus the Soyuz finally achieved the ability to do automatically what the Apollo had demonstrated manually fifteen years earlier.
The Soyuz has had a production run unequalled by any other spacecraft
(except Vostok derivatives used by Russia for military reconnaissance). It has been in continuous production for over twenty-five years, and will certainly continue in use to the end of this decade. By mid-1991 155 Soyuz and Progress spacecraft had accumulated the incredible total of twenty years of time in space, travelling over 4,800 million kilometers in the process. Reliability has improved continuously. While two crews lost their lives in the first five years of the program, there has been no loss of life since then, despite eight in-orbit emergencies and two aborts during launch. Ignored and maligned in the West, the Soyuz was the key that unlocked the door of space supremacy for the Soviet Union.