When the United States successfully landed men on the Moon in 1969, it changed the landscape of space exploration. In America, the success of Apollo left the space program searching for an ongoing purpose in the face of imminent cancellation. In the Soviet Union, losing the race to the Moon solidified the inertia that had dogged the country’s manned lunar landing efforts. In both nations, leaders were looking for the next big move in space, and in the Soviet Union, this next step became the Salyut space station.
In the Soviet Union, like in the United States, the advent of manned spaceflight had raised questions about the military’s role in space. Looking to give the military a platform in space, Vladimir Chelomei, Chief Designer from the OKB-52 design bureau, drew up a proposal for the Orbital Piloted Station (OPS). Announced on October 12, 1964, the project was code-named Almaz (or "diamond" in English), and was similar to the U.S. Air Force’s appropriate of NASA’s Gemini spacecraft for its own Manned Orbiting Laboratory program.
As the 1960s continued, efforts towards realizing Chelomei’s OPS were overshadowed by the race to the Moon. Almaz remained on the back burner until 1969, when the Soviet Union needed a new goal. But OKB-52 wouldn't see its design come to fruition, as Vasiliy Mishin of the rival design bureau TsKBEM proposed a civilian manned space station program that would leapfrog Almaz by cannibalizing the military program for parts.
The program, which was approved on February 9, 1970 and code named DOS-7K, created a space station made from the body of Almaz with modified parts and systems from Soyuz spacecraft. It was designed to launch unmanned; crews would follow it into orbit, docking with and then transferring to the main module for the duration of their orbital stay.
A model of the Salyut space station with a Soyuz spacecraft on one end and a Progress spacecraft on the other.
Once the first station was built, it was rechristened Salyut. It was a 65-foot long cylinder measuring 13 feet in diameter at its widest point. It was made of several components, three of which were pressurized and only two of which the crew could access. The total habitable space was about 3,531 cubic feet. Cosmonauts gained access to the station through a docking cone that would connect one end of the Soyuz spacecraft to one end of the station. The two habitable modules were a main module with eight consoles and 20 porthole windows, plus a second module that housed all communications and control systems including the life support and power supply systems. Between these two pressurized sections, crews would have all the necessary amenities to live and work in space, including dining and recreation areas, food and water storage, a toilet, control stations, exercise equipment, and scientific equipment. The third module that the crew had no access to housed the engine and all associated equipment.
To keep crews alive and the station humming, Salyut relied on two pairs of externally mounted solar panels that extended like wings from the smaller compartments at either end of the station. Salyut also had a heat regulation system, orientation and control devices, as well as chemical batteries and reserve supplies of oxygen and water.
Manning the Station
The first generation, Salyut 1, was launched on April 19, 1971. It beat NASA’s Skylab station into orbit by a little over two years; Skylab launched, also unmanned, on May 14, 1973. Only once it had launched did the Soviet Union announce its purpose as a test bed for future space station elements as well as a place for cosmonauts to conduct scientific experiments.
The three-man crew of Soyuz 10 was meant to be the first to occupy Salyut 1 on a 30 day mission. But after a successful launch on April 22, 1971, the mission was hampered by technical problems. The crew rendezvoused and soft docked with the Salyut station, but they couldn't manage a hard docking. The docking collar couldn't secure itself, which meant the crew couldn't safely board the station. The mission was aborted, but the technical problems didn't end. After difficulty separating from the station, toxic fumes seeped into the spacecraft during reentry. In spite of these issues, the crew was recovered in good health.
The subsequent Soyuz mission, Soyuz 11, launched two months later on June 6. The docking problems that had plagued Soyuz 10 didn't resurface, and the crew of Soyuz 11 spent 24 days living on board the Salyut 1 station. The crew ran a series of experiments, the majority of which focused on gathering data on human performance in weightlessness. It was clear the Soviets were looking ahead at longer duration missions.
The Salyut program hit a major setback at the end of the Soyuz 11 mission. During reentry, a ventilation valve failed and opened prematurely. The crew reentry capsule depressurized and the crew, wearing simple flight suits rather than pressure suits, were killed. The accident meant that changes be made not only to the Soyuz spacecraft but to the Soviet space policy as well. It was clear none of the major changes would come during Salyut 1’s lifetime. The station was deliberately deorbited, crashed into the Pacific Ocean on October 11, 1971.
The Russian-built Zarya module, core of the ISS and based on the core of the Almaz station, in orbit.
On April 3, 1973, the first Almaz station, OPS-1, was launched. To hide its true purpose, and to avoid admitting it was developing a military space station, the Soviets swiftly renamed the station Salyut 2 once it reached orbit. Thirteen days later, with a crew eagerly awaiting their own launch to the station, ground crews noticed a loss of pressure in the station. The official investigation found that faulty wiring had caused one of the lines in the station’s propulsion system to burst when the engine fired. The resulting plume had likely burned through the pressurized hull. But this theory fell apart with closer analysis of fragments found orbiting near the station. It turned out that the upper stage of the Proton rocket that had delivered the station to orbit had exploded. It was a stray piece of debris that had pierced the hull, causing the station to lose pressure. The station was never manned, and it fell back to Earth on May 28, 1973.
Another OPS military space station, OPS-2, was publicly announced as Salyut 3 when it launched a little over a year later on June 25, 1974. This new station featured novel developments, like an "electro-mechanical" attitude control system, rotating solar arrays, and separate areas for work and leisure. It also boasted a new water-recycling system. A large part of its payload was made of cameras that could observe the Earth in a variety of wavelengths. The station hosted two crews and one unmanned Soyuz capsule before it was deorbited on January 24, 1975.
Salyut 4 was launched on December 26, 1974, even before Salyut 3 was deorbited. This station was a copy of Salyut 1, though it was much more successful. Two crews. Soyuz 17 and Soyuz 18, occupied this station. It was also visited by an unmanned Soyuz spacecraft. It stayed docked for three months, proving Salyut could support long-duration manned visits. Salyut 4 was deorbited February 2, 1977, and re-entered the Earth's atmosphere the next day.
Salyut 5 was yet another military station. Called OPS-3, it took on its innocuous Salyut designation after launching on June 22, 1976. This big development on this station was a new radio that allowed data transmission in real-time to tracking stations on Earth. But it was also plagued with environmental problems. The Soyuz 21 crew was the first to visit the station and left early after complaining of a bad smell and headaches; mission controllers thought a toxic gas leak could be the culprit. The Soyuz 23 and 24 crews followed. The station was deorbited on August 8, 1977.
Working Towards Longevity
The last two Salyut stations, Salyuts 6 and 7, marked a shift in the program. These two functionally similar second-generation Salyut space stations were designed with longevity in mind. Both were built using Salyut 1 as a model and featured two docking ports. This was vital to long term missions, since having two docking ports meant an second Soyuz crew or an unmanned Progress spacecraft could dock with the station and resupply a resident crew during longer stays.
Both stations enjoyed great success. Salyut 6 operated between 1977 and 1982 (it was deorbited on July 29 of that year) during which time it hosted six long-term crews and ten additional short term that brought supplies for the resident crews. Salyut 7 stayed aloft between May 31, 1982 and November 21, 1985. It also hosted six resident crews and four short-term visiting crews.
The Almaz-based Functional Cargo Block, just above the Earth's horizon, as part of the ISS.
When Salyut 7 was deorbited on February 7, 1991, it ended the Salyut program. But the Salyut legacy was clear: it had proved the value of a modular design in space station, something the Soviet Union brought to its subsequent space station program, Mir.
The Almaz station, too, has its legacy in modern spaceflight. Though the last Almaz hardware was flown as Salyut 5, the core module of the military station evolved into Zarya, also called the Functional Cargo Block. This was the first piece of the International Space Station to reach orbit, and it’s still 200 miles above the Earth today.
Further Reading: Salyut on Astronautix; Salyut: The First Space Station by Grujica Ivanovich