The Soyuz 6

Soyuz 6 was part of a joint mission with Soyuz 7 and Soyuz 8 that saw three Soyuz spacecraft in orbit together at the same time, carrying seven cosmonauts. The crew of Georgi Shonin and Valeri Kubasov were meant to take high-quality movie photography of Soyuz 7 and Soyuz 8 docking but the rendezvous systems on all three spacecraft failed.
It is still not known exactly what the actual problem was, but it is often quoted as being a helium pressurization integrity test. The version of Soyuz spacecraft used for the missions (7K-OK) carried a torus shaped docking electronics equipment housing surrounding the motor assembly on the back of the service module. This is thought to have been pressurized with helium to provide a benign environment for the electronics. It was then jettisoned after docking to lower the mass of the spacecraft for reentry. What went wrong with the electronics on all three spacecraft is still not known.The crew was made up of Georgi Shonin and Valeri Kubasov, who carried out important experiments in space welding. They tested three methods: using an electron beam, a low pressure plasma arc and a consumable electrode. The apparatus was designed at the E. O. Paton Electric Welding Institute, Kiev, Ukraine. The weld quality was said to be in no way inferior to that of Earth based welds. After 80 orbits of the Earth they landed on October 16, 1969, 180 km northwest of Karaganda, Kazakhstan. The radio call sign of the spacecraft was Antei, referring to the Greek hero 'Antaeus,' but also a common diminutive of a Russian given name for boys. More important, at the time of the flight, however, it was also the name of the largest practicable aircraft, the Soviet Antonov 22, made in Ukraine. But unlike the call signs of Soyuz 7 and Soyuz 8, this was not the name of a squadron in Soviet military training, of uncertain role, for the one that begins with the letter 'a' is Aktif, meaning 'Active'.

Salyut 6 (DOS-5) (Russian: Салют-6; English translation: Salute 6) was launched on September 29, 1977. Although it resembled the previous Salyut stations in overall design, it featured several revolutionary advances including a second docking port where an unmanned Progress cargo spacecraft could dock and refuel the station. From 1977 until 1982 Salyut 6 was visited by five long-duration crews and 11 short-term crews, including cosmonauts from Warsaw Pact countries. 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. The very first long-duration crew on Salyut 6 broke a record set on board Skylab, staying 96 days in orbit. The longest flight on board Salyut 6 lasted 185 days. The fourth Salyut 6 expedition deployed a 10-meter radio-telescope antenna delivered by a cargo ship. 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. Salyut 6 was deorbited July 29, 1982.