Salyut programme

The Salyut programme (Салю́т,, Salute or Fireworks) was the first space station program undertaken by the Soviet Union, which consisted of a series of four crewed scientific research space stations and two crewed military reconnaissance space stations over a period of 15 years from 1971 to 1986. Two other Salyut launches failed. Salyut was, on the one hand, designed to carry out long-term research into the problems of living in space and a variety of astronomical, biological and Earth-resources experiments, and on the other hand this civilian program was used as a cover for the highly secretive military Almaz stations, which flew as well under the Salyut designation. Salyut 1, the first station in the program, became the world's first crewed space station.

Salyut broke several spaceflight records, including several mission duration records, the first ever orbital handover of a space station from one crew to another, and various spacewalk records. The Soyuz program was vital for evolving space station technology from basic, engineering development stage, single-docking port stations to complex, multi-ported long-term orbital outposts with impressive scientific capabilities, whose technological legacy continues to the present day. Ultimately, experience gained from the Salyut stations went on to pave the way for multimodular space stations such as Mir and the International Space Station, with each of those stations possessing a Salyut-derived core module at its heart.

Mir-2 (DOS- 8), the final spacecraft from the Salyut series, became one of the first modules of the ISS, and the first module of the ISS, Russian-made Zarya, relied heavily on technologies developed in the Salyut programme.

History of Salyut space stations
The program was composed of DOS (Durable Orbital Station) civilian stations and OPS (Orbital Piloted Station) military stations:


 * The Almaz-OPS space station cores were being designed since October 1964 by Vladimir Chelomei's OKB-52 organization as military space stations, long before the Salyut programme started. For Salyut, small modifications had to be made to the docking port of the OPS to accommodate Soyuz spacecraft in addition to TKS spacecraft.


 * The civilian DOS space station cores were being designed by Sergei Korolev's OKB-1 organization – Korolev and Chelomei had been in fierce competition in the Soviet space industry during the time of the Soviet manned lunar programs. In an effort by OKB-1 to catch up with OKB-52, they took Chelomei's Almaz-OPS hull design and mated it with subsystems derived from their own Soyuz. This was done beginning with conceptual work in August 1969. The DOS differed from the OPS modules in several aspects, with among others extra solar panels, front and (in Salyut 6 and 7) rear docking ports for Soyuz spacecraft and TKS spacecraft, and finally more docking ports in DOS-7 and DOS-8 to attach further space station modules.

When it was realized that the later started civilian DOS stations could not only offer a cover story for the military Almaz programme, but could be finished within one year (and at least a year earlier than Almaz), the Salyut programme was incepted on February 15, 1970 – under the condition that the manned lunar program would not suffer. However, the engineers at OKB-1 immediately switched from the L3 lunar lander effort, which was perceived as an dead-end, to start work on DOS – despite fears that it would kill the Soviet manned Moon shot. In the end it turned out that the Soviet N1 "Moon Shot" rocket never flew successfully, so OKB-1's decisions to abandon the ill fated Soviet manned lunar program, and to derive a DOS space station from existing Soyuz subsystems and an Almaz-OPS hull proved to be right: The actual time to the launch of the first DOS-based Salyut 1 space station from the get-go was an impressive 16 months – the world's first space station was launched by the Soviet Union, two years before Skylab or the first Almaz-OPS station flew.

Initially the space stations were to be named Zarya, the Russian word for 'Dawn'. Yet, as the launch of the first station in the program was prepared, it was realized that this would conflict with the call sign Zarya of the flight control centre (TsUP) in Korolyov – therefore the name of the space stations was changed to Salyut shortly before launch of Salyut 1.

While a total of nine space stations were launched in the Salyut programme, with six successfully manned, setting some records along the way, it was the stations Salyut 6 and Salyut 7 that became the workhorses of the program: Out of the total of 1,697 days of occupancy that all Salyut crews achieved, Salyut 6 and 7 accounted for 1,499. While Skylab already featured a second docking port, these two Salyut stations became the first that actually utilized two docking ports: This made it possible for two Soyuz spacecraft to dock at the same time for crew exchange of the station and for Progress spacecraft to resupply the station, allowing for the first time a continuous ("permanent") occupation of space stations.

The heritage of the Salyut programme continued to live on in the first multi-module space station Mir with the Mir Core Module ("DOS-7"), that accumulated 4,592 days of occupancy, and in the International Space Station (ISS) with the Zvezda module ("DOS-8"), that accumulated 4,310 days of occupancy. Furthermore the Functional Cargo Block space station modules were derived from the Almaz programme, with the Zarya ISS module being still in operation together with Zvezda.

Salyut 1 (DOS-1)
Salyut 1 (DOS-1) (Салют-1; Salute 1) was launched April 19, 1971. It was the first space station to orbit Earth.

Its first crew launched in Soyuz 10 but were unable to board it due to a failure in the docking mechanism; its second crew launched in Soyuz 11 and remained on board for 23 productive days. The world's first successful manning of a space station was however overshadowed when the crew was killed during re-entry of the Soyuz 11 capsule on October 11, 1971 – a pressure-equalization valve in the reentry capsule had opened prematurely, suffocating all three.

Salyut 1 was moved to a higher orbit in July and August 1971 to ensure that it would not be destroyed prematurely through orbital decay. In the meantime, Soyuz capsules were being substantially re-designed to allow pressure suits to be worn during launch, docking maneuvers, and reentry. However, Salyut 1 ran out of supplies before the Soyuz redesign effort was concluded, and it was decided to fire the engines for the last time on October 11, to lower its orbit and ensure prompt destructive re-entry over the Pacific Ocean. After 175 days in space, the first real space station came to an end.

DOS-2
DOS-2 was launched on July 29, 1972. It was similar in design to Salyut 1. The second stage of its Proton rocket failed – DOS-2 never reached orbit and crashed into the Pacific Ocean.

Salyut 2 (OPS-1, military)
Salyut 2 (OPS-1) (Салют-2; Salute 2) was launched April 4, 1973. The space station was – despite its "Salyut 2" designation – slated to be the first military space station, part of the highly classified Almaz military space station program – the Salyut designation was chosen to conceal its true nature. Although it launched successfully, within two days the as-yet-unmanned Salyut 2 began losing pressure and its flight control failed; the cause of the failure was likely due to a shrapnel from the discarded and exploded Proton rocket upper stage that pierced the station. Furthermore, on April 11, 1973, 7 days after launch, an unexplainable accident caused both solar panels to be torn loose from the space station, cutting off all power. Salyut 2 re-entered on May 28, 1973.

Cosmos 557 (DOS-3)


The module DOS-3 was launched on May 11, 1973 – three days before the launch of Skylab – slated to become next civilian space station with an Salyut designation. Due to errors in the flight control system while out of the range of ground control, the station fired its orbit-correction engines until it consumed all of its fuel. Since the spacecraft was already in orbit and had been registered by Western radar, the Soviets disguised the launch as "Cosmos 557" – it was revealed to have been a Salyut station only much later. It re-entered Earth's atmosphere a week later, and burned up on re-entry.

Salyut 3 (OPS-2, military)


Salyut 3 (OPS-2) (Салют-3; Salute 3) was launched on June 25, 1974. It was another Almaz military space station, this one launched successfully. It tested a wide variety of reconnaissance sensors, returning a canister of film for analysis. On January 24, 1975, after the station had been ordered to deorbit, trials of the on-board 23 mm Nudelman aircraft cannon (other sources say it was a Nudelman NR-30 30 mm gun) were conducted with positive results at ranges from 3000 m to 500 m. Cosmonauts have confirmed that a target satellite was destroyed in the test. The next day, the station was ordered to deorbit. Only one of the three intended crews successfully boarded and crewed the station, brought by Soyuz 14; Soyuz 15 attempted to bring a second crew but failed to dock. Nevertheless, it was an overall success. The station's orbit decayed, and it re-entered the atmosphere on January 24, 1975.

Salyut 4 (DOS-4)


Salyut 4 (DOS-4) (Салют-4; Salute 4) was launched on December 26, 1974. It was essentially a copy of the DOS-3, and unlike its ill-fated sibling it was a complete success. Two crews made stays aboard Salyut 4 (Soyuz 17 and Soyuz 18), including one of 63 days duration, and an unmanned Soyuz capsule (Soyuz 20) remained docked to the station for three months, proving the systems' long-term durability. Salyut 4 was deorbited February 2, 1977, and re-entered the Earth's atmosphere on February 3.

Salyut 5 (OPS-3, military)
Salyut 5 (OPS-3) (Салют-5; English translation Salute 5) was launched on June 22, 1976. It was the third and last Almaz military space station. Its launch and subsequent mission were both completed successfully, with three crews launching and two (Soyuz 21 and Soyuz 24) successfully boarding the craft for lengthy stays (the second crew on Soyuz 23 was unable to dock and had to abort). Salyut 5 reentered on August 8, 1977.

Following Salyut 5 the Soviet military decided that, with the advent of the era of spy satellites, the tactical advantages were not worth the expense of the program and withdrew – the focus for the later Salyut stations became civilian research and prestige for the Soviet Union.

Second generation – Long-duration inhabitation of space
In 1977 another marked step forward was made with the second generation of Salyut stations: The aim was to continuously occupy a space station with long-duration expeditions, for the first time in spaceflight.

Although Salyut 6 and Salyut 7 resembled the previous Salyut stations in overall design, several revolutionary changes were made to the stations and program for the aim of continuous occupation: The new stations featured a longer design life and a second docking port at the aft of the stations – crew exchanges and station "hand overs" were now made possible by docking two crewed Soyuz spacecraft at the same time. Furthermore, the uncrewed Progress space station resupply craft was created based on the crewed Soyuz spacecraft, to resupply crew and station with air, air regenerators, water, food, clothing, bedding, mail, propellants, pressurant, and other supplies – while the Progress docked to the station's second docking port, the crew's Soyuz spacecraft could remain docked to the station's first port. The Progress spacecraft can even deliver hardware parts for updating the onboard experiment apparatus and even permitting to perform repairs of the station if needed, furthermore extending the stations life.

The space station program had matured: Flights of both crews and cargo to a space station had become common, and the Salyut stations – first Salyut 6 from 1977 to 1981, and then Salyut 7 from 1982 to 1986 – were crewed continuously for a considerable part of the time.

Salyut 6 (DOS-5)


Salyut 6 (DOS-5) (Салют-6; Salute 6) was launched on September 29, 1977. Salyut 6 was visited from 1977 until 1981 by 16 manned spacecraft, bringing five long-duration crews ("expeditions") and 11 short-term crews. The very first long-duration crew on Salyut 6 broke a record set on board Skylab, staying 96 days in orbit. The short-term crews included foreign cosmonauts from the Interkosmos programme setting several firsts: the first citizen in space of a nation other than the United States or the Soviet Union, the first black and Hispanic person in space and the first Asian person in space. The longest flight on board Salyut 6 lasted 185 days. The fourth Salyut 6 expedition deployed a 10-meter radio-telescope antenna delivered by an uncrewed cargo spacecraft.

After Salyut 6 manned operations were discontinued in 1981, a heavy unmanned spacecraft called TKS and developed using hardware left from the canceled Almaz program was docked to the station as a hardware test. Some unconfirmed reports say the station was functionally capable of even more missions and years, but combating the ever-increasing mold in living quarters was becoming impossible, and in practice caused the retirement decision. Salyut 6 was deorbited July 29, 1982.

Salyut 7 (DOS-6)


Salyut 7 (DOS-6) (Салют-7; Salute 7) was launched on April 19, 1982. DOS-6 was built as the back-up vehicle for Salyut 6 with very similar equipment and capabilities, though several more advanced features were included. The station was aloft for eight years and ten months, during which time it was visited by 10 manned spacecraft bringing six long-duration crews ("expeditions") and 4 short-term crews (including French and Indian cosmonauts in the Interkosmos programme).

On 12 February 1985, during an unmanned period, contact with Salyut 7 was lost. The station had become crippled by electrical problems, all systems did shut down and the station began to drift. It was decided to put together a salvage mission, and in June 1985 the Soyuz T-13 mission, in what was in the words of author David S. F. Portree "one of the most impressive feats of in-space repairs in history," managed to bring the station online again.

The Soyuz T-15 mission was the last to visit Salyut 7 in 1986, ferrying equipment from Salyut 7 to the new Mir space station; This was so far the only ferry flight between two space stations.

Aside from the many experiments and observations made on Salyut 7, the station also tested the docking and use of large modules with an orbiting space station. These modules, called "Heavy Cosmos modules", helped engineers develop technology necessary to build Mir.

Salyut 7 was finally deorbited on February 7, 1991.

Salyut's heritage – Modular space stations
After the second generation, plans for the next generation of Salyut stations called for the cores DOS-7 and DOS-8 to allow, for the first time in spaceflight, the addition of several modules to a station core and to create a modular space station. For this, the DOS modules were to be equipped with a total of four docking ports: one docking port at the aft of the station as in the second generation Salyuts, and the replacement of the front docking port with a "docking sphere" containing a front, port and starboard docking port.

While the station cores DOS-7 and DOS-8 were build and flown, they never received the Salyut designation; Instead, DOS-7 evolved into the Mir Core Module for the Mir space station that followed the Salyut programme, and DOS-8 was used as the Zvezda Service Module for the International Space Station (ISS) which followed Mir.

And the heritage from the Almaz program is present even today. While in 1976 the last space station from the Almaz programme was flown with Salyut 5, the development of the Almaz TKS spacecraft evolved into the Functional Cargo Block, becoming the first space station modules with the ISS Zarya Functional Cargo Block being in orbit still today.

Mir Core Module (DOS-7)


DOS-7 continued to be developed during Salyut 7, becoming the Mir Core Module of the Mir space station – the first modular space station, with crewed operations from 1986 to 2000.

The station featured among others upgraded computers and solar arrays and accommodations for two cosmonauts each having their own cabin. A total of six docking ports were available on the Mir Core Module, which were used for space station modules and visiting spacecraft – the docking sphere design had been upgraded from its initial Salyut design to contain the maximum of five docking ports (front, port, starboard, zenith and nadir). And finally, the modules for the Mir space station were derived from the Functional Cargo Block design of the Almaz programme.

The name of the Mir space station – Мир, literally Peace or World – was to signify the intentions of the Soviet Union to bring peace to the world; It was however during the time of the Mir space station that the Soviet Union was dissolved in 1991, ending what was began with the 1917 October Revolution in Russia. This dissolution had started with the Soviet "perestroika and glasnost" ("restructuring and openness") reform campaigns by Soviet leader Mikhail Gorbachev in the 1980s, had reached an preliminary endpoint with the revolutions of 1989 and the end of the communist Eastern Bloc (Warsaw Pact and the CoMEcon), finally to reach the Soviet Union itself in 1991.

While the Russian Federation became the successor to much of the dissolved Soviet Union and was in a position to continue the Soviet space program with the Russian Federal Space Agency, it faced severe difficulties: imports and exports had steeply declined as the economic exchange with CoMEcon nations had crumbled away, leaving the industry of the former Soviet Union in shambles. Not only did the political change in east-Europe signify an end of contributions to the space program by east-European nations (like from the east-German Carl Zeiss Jena), but parts of the Soviet space industry were located in the newly independent Ukraine, which was similarly cash-strapped as Russia and started to demand hard currency for its contributions.

It was during this time of transition and upheaval that the Shuttle–Mir Program was established between the Russian Federation and the United States in 1993. The former adversaries would now cooperate, with "Phase One" consisting of joint missions and flights of the US Space Shuttle to the Mir space station. It was a partnership with stark contrasts – the Russian needed an inflow of hard currency to keep their space program aloft; In the US it was seen as a chance to learn from the over 20 years of experience of Soviet space station operations, and jumpstart the US space station program.

It was "Phase Two" of this Shuttle-Mir Program that would lead to the International Space Station.

Zvezda ISS Service Module (DOS-8)


DOS-8 evolved into the Mir-2 project, intended to replace the Mir space station. Finally, it became the International Space Station (ISS) Zvezda Service Module and formed the core of the early ISS space station – together with the Zarya module (which was derived from Almaz Functional Cargo Block designs).

Data table
All data for Zvezda (DOS-8).