Remembering Mir 20 Years Later

20 years ago this week, the Mir space station returned to Earth in a blaze of glory.

For years, Mir’s crews had struggled to keep the station running despite its seeming determination to fall apart: coolant leaks, life support system breakdowns, electronics crashes, and power glitches had plagued the station since the late 1990s. In 1994, a Progress cargo ship had crashed into the Spektr module, damaging it beyond repair.

Mir had been empty since 1999 when its final visitor arrived: a Progress cargo ship, loaded with extra fuel, docked with the abandoned station and used its thrusters to slow the station’s orbit enough that Earth’s gravity could pull it down into the atmosphere. The thruster guidance ensured that the several-ton station entered above the south Pacific, so that whatever pieces didn’t burn up in the friction of atmospheric entry plunged into the watery depths of the spaceship graveyard instead of crashing into cities or farmland.

The space station weathered the fall of a global superpower and became humanity’s first long-term outpost in orbit. It also heralded the beginning of the modern era of space architecture and laid the groundwork for building the International Space Station.

Modular Construction Goes To Space

ISS was built gradually, with each module or construction element getting launched separately and then connected to the others. That modular design allowed launch mass to be spread out, so that you eventually could launch a bigger station by doing some of the assembly once the pieces were in space. But the idea originated with Mir.

Mir’s predecessors, the Soviet Salyut stations and the American Skylab station, were much smaller and relatively much simpler spacecraft, built and launched as single units for much shorter missions. But with Mir, Soviet engineers envisioned something much more complex — and much larger.

Mir’s core module launched on February 19, 1986, and over the next decade, Russian rockets – and eventually a couple of American space shuttle flights – delivered six more pressurized modules and an assortment of girders, trusses, and external racks for mounting science experiments. The first four modules docked with the core module, which held the crew’s living space, the station’s main environmental control, and its main engines. Think of each module as a room (or, usually, a suite of rooms) where crew members lived and worked, and like the rooms in most houses, each module was designed and equipped for different activities.

The Kvant-1 expansion module, for instance, was designed for astrophysics; its 1987 installation added three compartments to the station’s core, and it came fitted with x-ray and ultraviolet telescopes, an x-ray and gamma ray detector, a wide-angle camera, and other instruments for astrophysics observations and experiments. And in 1996, the Priroda module boasted a large synthetic aperture radar dish and other instruments for studying the surface of Earth from above.

But sometimes modules served an eclectic combination of purposes. Kvant-2 in 1989 added an airlock equipped with a thruster-powered maneuvering suit for spacewalking cosmonauts, along with storage space for cargo and an assortment of scientific experiments such as an incubator for quail eggs – but it also added water storage, showers, and a system for purifying urine back into usable water (which should probably not be done in the same room where you’re incubating your quail eggs under normal Earthbound circumstances).

By the time it all came together, Mir contained 350 cubic meters of pressurized crew space inside its 129,700-kilogram hull. The station stretched 19 meters along one axis, from the core module to Kvant-1; 31 meters along another axis from the Priroda Earth observation module to the docking module; and 27.5 meters along a third axis from the Kvant-2 module with the water systems to the Spektr module that housed visiting Americans.

At its peak, the station was the largest spacecraft humanity had ever put into orbit, and it would have been impossible to launch all in one piece. Modularity had become the next big thing in space station design.

Bird’s Eye Witness To The End Of An Era

On October 2, 1991, two cosmonauts blasted off from the USSR’s Baikonur Cosmodrome in the Soviet administrative unit of Kazakhstan. Both had been citizens of the Soviet Union all their lives, but that Christmas, as they orbited 350 miles above their homeworld, the USSR lowered its flag for the last time. Kasakhstan had declared its independence a few days before. Nearly six months later, on March 25, 1992, the cosmonauts returned to a different world as citizens of a new country, the Russian Federation – and employees of a newly renamed and reorganized national space agency.

A replacement crew had launched from Baikonur Cosmodrome, now situated in a newly-independent Kazakhstan, on March 17. On the surface, it looked as if work aboard Mir would carry on unruffled by the changing political winds, and to some extent, it did. Replacement crews kept rotating in, uncrewed resupply ships kept docking, and science experiments kept running.

But the final collapse of the Soviet Union had plunged Russia and the USSR’s former constituent republics into economic turmoil, and that took its toll on Mir and its crews. The station’s last two modules, Spektr and Priroda, had been expected to launch soon, but the new nation’s economic woes put them on hold for several more years.

Worse, cosmonauts noticed that although the uncrewed Progress cargo ships that brought new supplies and science experiments to Mir kept arriving on schedule, they often arrived with items missing. Some of the missing cargo could be chalked up to supply shortages, but some of it seemed to have been stolen. Meanwhile, newly-independent Ukraine had redirected the fleet of ships whose radio antennae usually tracked the space station and provided more regular communications with Earth.

But although the end of the Soviet Union brought upheaval, it also brought new friends. A 1992 agreement put Russian cosmonauts on space shuttle missions and American astronauts aboard Mir, and starting in 1993, American space shuttle missions helped ferry modules and supplies to the Russian space station as part of the Shuttle-Mir program.

Like Mir’s physical design, the Shuttle-Mir program provided a roadmap for the international effort that would eventually build the ISS. Like modularity, international cooperation in space had become the next big thing in space station design.

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