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.
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.
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.
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.
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.
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