By the latter half of the Space Race between the United States and the USSR, focus had shifted from simply putting people into orbit to seeing how long they could stay up there. And while the U.S. won the sprint to the moon, it was actually the Russians who won the endurance test with the Salyut 7 space station.
The Salyut program was the Soviet Union's seven answers to Skylab. The first Salyut launched in 1971, the last in 1982. The early models were all monolithically constructed and launched in a single piece aboard Proton rockets into Low Earth Orbit. Salyut 7 marked a significant departure from this method, though, by being the first Soviet station to employ a modular design. And that wasn't the only improvement.
The Salyut 7 was originally designed as a backup to its predecessor the Salyut 6 and therefore offered very similar capabilities. In fact, the only reason Salyut 7 was launched at all was because the Mir program had fallen behind schedule.
The Salyut 7 measured 52 feet long by 13 feet wide with 295 cubic feet of pressurized interior space when fully assembled. Per NASA:
It had two docking ports, one on either end of the station, to allow docking with the Progress unmanned resupply craft, and a wider front docking port to allow safer docking with a Heavy Cosmos module. It carried three solar panels, two in lateral and one in dorsal longitudinal positions, but they now had the ability to mount secondary panels on their sides. Internally, the Salyut 7 carried electric stoves, a refrigerator, constant hot water and redesigned seats at the command console (more like bicycle seats). Two portholes were designed to allow ultraviolet light in, to help kill infections. Further, the medical, biological and exercise sections were improved, to allow long stays in the station. The BST-1M telescope used in Salyut 6 was replaced by an X-ray detection system
It launched in April of 1982 and set into its orbit while still unmanned. The station's first crew arrived in May and would be followed by five more during the Salyut's record-breaking 8-year, 10-month service life (beating out Skylab's record by more than a year). The Salyut 7's crews broke similar endurance records when cosmonauts Leonid Kizim, Vladimir Solovyov, and Oleg Atkov hopped aboard for a 237-day stay in 1984.
However, despite its larger accommodations and increased research capacity, the Salyut 7 was not without its share of technical difficulties. A trio of fuel line leaks discovered by the third crew in 1983, for example, wound up requiring not one but four EVAs (spacewalks) and the delivery of a custom made tool to resolve.
Then there was the time in 1984 when all three crew members "hallucinated" that the station was surrounded by a bright orange cloud of gas. Ground control chalked the incident up to a mix of pressure and temperature fluctuations combined with a shortage of oxygen within the crew capsule but not aliens. Definitely not aliens.
And in 1985, the Salyut 7 faced its more dangerous challenge when, during a crew changeover, the uninhabited station suddenly lost power and began to drift out of its orbit. In what has been described as "one of the most impressive feats of in-space repairs in history" a pair of cosmonauts manually docked with the station using handheld laser rangefinders (as the autodocking feature was offline) and conducted their inspections while wearing parkas and cold-weather to guard against the freezing temperatures of the station's interior. Then, after finding and fixing the root of the problem—a faulty sensor that monitored the charge status of the station's batteries—the two then had to spend a couple of days cramped together in a Soyuz capsule waiting for the station to recharge and reheat.
Still, these technical challenges only served to further improve the Russian cosmonaut program and their ability to deal with the terrifying variety of things that can go wrong outside the comfy confines of the Earth's atmosphere. These lessons, and much of the equipment aboard the Salyut 7, were transferred over to the Mir space station in 1986. The last Salyut received its last salute just before burning up in the atmosphere over the South Pacific ocean in 1991. [NASA - NASA - Wiki]