What it was: The next in in the long line of increasingly large and sophisticated Soviet space stations that stretched from Salyut 1 in 1971 to Mir in 1986.
Details: Mir is the least-heralded of the major space firsts. Sputnik-1 and Yuri Gagarin rightly retain their fame, and of course the United States can answer with Apollo 11. Yet of the “big five” goals of the early manned space programs (the fifth being the still-yet unclaimed manned Mars landing) Mir fulfilled one: the first “real” space station. There had been other stations before, as far back as Salyut 1 and Skylab in the early 1970s, but they were not what was envisioned when an orbital outpost had first been seriously discussed in the late 1950s. Unlike the earlier single-piece stations Mir was the first “building” in space, in the literal sense of the word, constructed out of multiple components sent up over time and joined to make a functional whole. Salyut 7 had had one experimental module (TKS-4) attached after launch, but Mir was the real thing.
The station was built around the so-called Base Module (DOS-7), the ultimate version of the DOS framework derived from Vasili Mishin’s civilian Salyuts and Vladimir Chelomei’s Almazes. While it was being built the Soviets also built a backup base module, DOS-8, in case something went wrong with the first one. From the beginning, though, they were also making plans for what to do with the backup if DOS-7 and its launch went as planned. When they did, DOS-8 definitely became the centrepiece of a second space station.
At first Mir-2 was to have been “just another Mir”, which is not too surprising considering that they shared the same design for the core module. The only major difference between the two was the addition of a truss extending from the end of the station, greatly increasing its length, for solar panels and other equipment. But in 1982 Leonid Brezhnev died and was replaced by Yuri Andropov; in the United States, Ronald Reagan had become president the year previous and four months after Andropov’s takeover the US leader initiated the Strategic Defense Initiative. Andropov chose to fight fire with fire, and the Soviet space program was re-oriented to deal with the newly perceived threat. Mir-2 began to change.
There were actually several major redesigns of the station before 1993. One was still fairly close to the original Mir, in that most of its modules were designed to be lifted by Proton rockets and so had to stay in the 20-tonne range. But the station’s solar panels and a larger core module were designed with Energia in mind, and could range up to ninety tonnes. In fact the Energia’s first test payload the space weapon testbed Polyus, which was hurriedly cobbled together from several pieces of equipment, was in part based on a test article of the proposed Mir-2 core. The truss was also turned into a long docking tunnel meaning that one more manned ship or supply craft could visit this version of Mir-2 as compared to the original.
While that design went a fair distance, by the end of the 80s Mir-2 had grown again into what was formally called the Orbital Assembly and Operations Center but generally referred to as “Mir 2.0”. The first two designs had belonged to the Fili Branch of TsKBM, which is to say largely the Almaz design bureau that had been taken from Vladimir Chelomei after the death of his Politburo supporter Andrei Grechko. This version of the station was entirely NPO Energia’s baby and so under the close watch of Valentin Glushko.
The new design was similar in appearance to the largest of all the American designs for their space station Freedom, the dual-keel arrangement proposed by McDonnell-Douglas in 1986; Mir 2.0 was to have been constructed around a rectangle made of four trusses. After the launch of DOS-8, Energia rockets would do the rest of the work: a 90-ton core module, then the truss and solar panels, then three more launches carrying three more 90-ton modules. The modules and the solar panels would be attached to a cross-beam on the truss, while various pieces of equipment would be balanced around the rectangle to balance tidal forces as the station orbited Earth.
By the time Mir 2.0 was getting really underway though, the ground had shifted again. Andropov and his successor Konstantin Chernenko were gone, replaced by Mikhail Gorbachev. The US and the Soviet Union had begun reducing their nuclear arsenals with the INF Treaty, Eastern Europe had cut ties with the Soviet Union, and the USSR itself was in an economic collapse. Now Mir-2’s design started heading in the other direction.
“Mir 1.5” was once again based on the DOS-8 block. Dedicated Energia launches were no longer in the picture, so smaller modules in the seven tonne range were assumed now. The real twist was that now DOS-8 was to be launched sometime around 1994 along with the second flight of the Soviet shuttle Buran—its first manned mission. Using the orbiter’s robotic arm, DOS-8 would be maneuvered to join up with the original Mir station; a power module and a biotechnology module would be launched and automatically docked later. When those were all in place, some two years later, DOS-7 would be detached and allowed to deorbit. The newly hatched station would then be built up with additional modules (including a second biotech lab) and a long cross-truss on which to attach solar panels and some equipment, the latter brought by another flight of Buran. This version of Mir-2 would see the second Soviet shuttle (supposedly to be named Burya) arrive every six months to swap out the biotechnology modules, returning their manufactured goods to Earth.
Then the USSR came apart completely. Toward the end of 1993 Mir 1.5 was no longer going to begin its life attached to the original Mir. It was down to just four modules at this point, and would hold a crew of two. By this point, except for the cross-truss, it was largely the same model as Mir, made better primarily by the experience of building the first station.
What happened to make it fail: By then the Soviet Union itself had come apart, and the Russian economy was approaching its nadir, contracting something like 40% in the first half of the 90s. Meanwhile, the American space station Alpha was in very severe trouble. In March of 1993 the new President Bill Clinton had told NASA to look at bringing Russia into the space station effort (which, while primarily American, was also being supported by the ESA, Japan, and Canada). On November 1 of the same year NASA and the Russian Space Agency agreed to merge Mir-2 and Alpha into the International Space Station.
What was necessary for it to succeed: In a sense it did. The third piece of the ISS was the Russian module Zvezda, which is in fact the well-travelled DOS-8 block. Altogether there are five Russian pieces to the ISS as of this writing and, while most of them are newly designed for this station, one more beyond DOS-8 has its roots in the older project: the Rassvet module is built on the repurposed hull of the SPP module which was to have powered the final redesign of Mir 1.5 prior to its folding into the international effort.
For that matter, the ISS is due to be decommissioned sometime after 2020. In 2008, Roscosmos informed the US that they intend to detach some of their modules—both already in space and planned to be attached to the ISS between now and then—starting in the late 2010s and use them as the core of a new station, OPSEK (“Orbital Piloted Assembly and Experiment Complex”, in Russian). One of the modules to be detached is DOS-8, and the designs of OPSEK seen to date bear a family resemblance to Mir’s once-proposed descendant.