SPACESTATION

SPACE STATION

Salyut and Skylab were the first spacecraft designed as space stations. Orbiting the earth for extended periods, while crews came and went on other vehicles, these space stations made possible many valuable new experiments and astronomical observations. The Soviet station, Mir, which was expected to have a useful life of 5 years, was still manned and in orbit 12 years after its launch. The long-term success of Mir led to joint efforts toward an international space station.

Salyut Program.

The Soviet Salyut 1 space station, weighing 18,600 kg (41,000 lb), was launched on April 19, 1971. Three days later Soyuz 10, with a crew of three cosmonauts, rendezvoused and docked. For some unspecified reason, however, the cosmonauts did not enter the Salyut but undocked and returned to earth. In June Soyuz 11 joined with Salyut 1, and the three-man crew moved into the station to set a human spaceflight duration record of 24 days. A large variety of earth-resources and biological experiments was conducted. During the return journey to earth, however, tragedy struck, and upon landing the three cosmonauts—Georgi T. Dobrovolsky (1928–71), Vladislav N. Volkov (1935–71), and Viktor I. Patsayev (1933–71)—were found dead, victims of an air leak. Because they wore no space suits, the cosmonauts had been killed quickly by the sudden depressurization. The Soviet program suffered another setback when the Salyut 2 space station, launched in April 1973, apparently went out of control, shedding various parts in orbit.

Thereafter, however, the Soviet Union sent up Salyut 3 (June 1974–January 1975), 4 (December 1974–February 1977), and 5 (June 1976–August 1977). Salyut 6 (September 1977–July 1982) and 7 (launched April 1982) were visited by a large number of international crews, including Cuban, French, and Indian cosmonauts and the first woman to perform extravehicular activity, Svetlana Savitskaya (1947–    ), during the flight of Soyuz T-12 on July 17–29, 1984. One of the most notable flights of the Salyut/Soyuz series occurred in 1984 when cosmonauts Leonid Kizim (1942–   ), Vladimir Solovyov (1947–   ), and Oleg Atkov (1950–   ), spent 237 days aboard the Salyut 7 before returning to earth, the longest space flight to that date. Unused since 1986, Salyut 7 plunged to earth in February 1991.

Skylab Program.

The U.S. Skylab program was much more extensive and complex than the Soviet Salyut program. Skylab, launched by the first two stages of a Saturn 5 rocket, weighed 88,900 kg (196,000 lb), nearly five times the weight of Salyut. In contrast to the estimated 99-cu m (3500-cu ft) interior space of Salyut, Skylab had 357 cu m (12,600 cu ft), about three and one-half times greater. Skylab served as a laboratory in earth orbit. It was used to make solar-astronomical studies, to make long-duration medical studies of the three-man crew, to make extensive multispectral observations of the earth, and to conduct a variety of scientific and technological experiments, such as metallic-crystal growth in the weightless state.

Skylab was damaged during launch on May 25, 1973, but the crew, veteran astronaut Conrad, Comdr. Joseph P. Kerwin (1932–    ), and Comdr. Paul J. Weitz (1932–    ), all of the navy, carried out EVA repairs, erected a heat-shielding canopy over the exterior of the spacecraft, and freed a jammed solar panel. Their flight lasted 28 days. A second crew spent 59 days in orbit; the third and final crew, 84 days. The Skylab project was considered completely successful. More than 740 hr were spent in observing the sun by telescopes, and 175,000 solar pictures were returned to earth, as were about 64 km (about 40 mi) of electronic data tape and 46,000 photographs of the earth’s surface. On July 11, 1979, during its 34,981st orbit, Skylab plunged to earth, raining fiery debris over sparsely populated western Australia and over the Indian Ocean.

The U.S., in cooperation with Canada, Japan, and the European Space Agency, planned a permanent space station to be assembled in space as a successor to Skylab, but delays and cost overruns led to cancellation of the project.

Mir.

The Mir space station, which the Soviets designed as a successor to the Salyut series, was launched on Feb. 20, 1986. Described by the Soviets as the core of the first permanently occupied space station, it featured six docking ports and could be operated by two cosmonauts. In 1987, Col. Yuri Romanenko (1944–    ) spent 326 days aboard Mir, the longest space flight then on record. On April 12, 1987, the Soviets succeeded in docking Mir with Kvant, an 18,000-kg (40,000-lb) astrophysics module. Carrying four X-ray telescopes, the Kvant was designed to link with Mir and observe a newly discovered supernova. (X rays from the exploding star, blocked by the earth’s atmosphere, could not be detected from earth.) In 1987–88, Soviet cosmonauts Vladimir Titov (1947–    ) and Musa Manarov (1956–    ) set a new record for time spent in space—366 days; the record was raised to 439 days by Russian cosmonaut Valery Polyakov (1942?–    ) in 1995. By that time, more than 20 Soyuz missions to the station had been accomplished.

International Cooperation.

The U.S. and Russian space station programs were formally joined in 1993. U.S. space shuttle craft began docking regularly at Mir, and U.S. astronauts began spending extended visits in preparation for future space station missions. In 1996 NASA and the Russian, European, Japanese, and Canadian space agencies agreed to cooperate on an International Space Station (ISS), designed to be a multinational research complex.

Construction of the station, based on the existing space shuttle and Mir programs, was originally scheduled to begin in late 1997. In that year, however, serious problems occurred aboard Mir. In February an air-filtering unit caught fire and burned for several minutes, in the worst space fire on record; the following month two oxygen generators malfunctioned. On June 25, in the worst collision in the history of human space flight, the station lost between 40 and 50 percent of its power supply in a crash with an unmanned cargo craft during a practice docking maneuver; none of the three Mir crew members (including one U.S. astronaut) was injured. A Russian commission blamed the accident on an overworked crew and inadequate training, among other factors, but some U.S. analysts raised questions about the safety of the aging craft. In June 1998 the U.S. space shuttle Discovery made the last scheduled shuttle mission to Mir, which was expected to remain in service through 1999.

Problems with Mir and other aspects of the Soviet space program delayed the ISS project by a year. In November 1998 Russia launched the first component of the space station, a propulsion and power module called Zarya. Two weeks later the U.S. launched the space shuttle Endeavour, carrying the space station’s large core unit, called Unity, which was attached to Zarya; Unity will serve as the principal connector for future pieces of the station. In-orbit assembly of the ISS is scheduled for completion by 2004.