Space Stations

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Space Stations

Overview

The advent of space stations allowed humans to spend extended periods of time in space. They have provided a wealth of information about the challenges humans will face, and must overcome, if they are to survive outside Earth's life-supporting atmosphere while traveling to distant planets or one day inhabiting other worlds. The Salyut 1, launched in 1971 by the Soviet Union, became the first manned space station. The United States followed two years later with its version, called Skylab. As the end of the twentieth century neared, the United States, Russia (part of the former Soviet Union), Canada, Japan, Brazil, and the 11 nations of the European Space Agency combined efforts to plan construction of the International Space Station (ISS). The ISS is scheduled to be completed in 2004.

Background

The space race between the United States and the Soviet Union began when the world's first satellite, Sputnik, went into orbit around Earth on October 5, 1957. The launch date marked the 100th year after the birth of Russian rocketry pioneer Konstantin Tsiolkovsky (1857-1935), who in 1903 proved that a missile could escape Earth's atmosphere using a staged rocket design and liquid propellants. The 185-pound Russian Sputnik—the name means traveler—orbited the planet some 1,400 times during its 96-day mission.

Sputnik's successful mission came at a time when the Cold War raged between the United States and Soviet Union. Many Americans felt the satellite gave the Soviets the military and technological upper hand. In 1961 U.S. President John F. Kennedy announced the country's intention to put a man on the moon. Although he subsequently supported a joint American-Soviet effort, it didn't materialize. After Kennedy's assassination in 1963, the American government pursued a solely American mission, and in 1969 American astronauts put the first human footprints on the lunar surface.

The Russians, then, were the first to put a satellite into orbit and the Americans were the first to put a human on the moon. In late 1969, shortly after the lunar landing, the Soviet Union announced plans to build, launch, and man the first space station. Construction began in 1960, and on April 19, 1971, the Earth-orbiting space station named Salyut 1 was launched. The 43-foot-long (13.1-meter), 20-ton (18.16 tonne) Salyut 1 was basically a series of three pressurized cylinders for use by cosmonauts and one nonpressurized cylinder for propellant storage. The pressurized cylinders included living and working quarters, various station controls and communications, and an access module. The access module was designed to connect with Soyuz spacecraft, which would ferry cosmonauts to and from the station.

On June 7, 1971, the Soyuz 11 brought the first cosmonauts to the Salyut 1. The two craft linked successfully, and three cosmonauts moved into the station for a 23-day stay. The team of cosmonauts was comprised of test engineer Viktor I. Patsayev, Lieutenant Colonel Georgi T. Dobrovolsky, and flight engineer Vladislav N. Volkov. This was Volkov's second Soyuz mission, and the first for Dobrovolsky and Patsayev. Before becoming a cosmonaut, Dobrovolsky was a fighter pilot and Patsayev was a design engineer. During the next three weeks and two days, the cosmonauts conducted a variety of equipment checks, performed medical and biological studies on plants and animals, and completed astronomical observation work.

During what became the longest manned space mission to date—the former record was held by cosmonauts aboard the Soyuz 9—the three cosmonauts took on hero status back at home. On June 30 the mission ended and the crew reboarded the Soyuz 11 for the return trip. As the Soviet Union was finishing plans to celebrate the mission's success, tragedy struck. The return trip appeared to go as planned, and the Soyuz 11 descent module landed as expected. When the recovery group reached the craft and opened its hatch, however, the group found all three men dead. Ensuing investigations revealed that a valve connecting the Soyuz 11's descent and orbital modules had become unfastened, and the descent module's pressurized atmosphere escaped into space. The limited space inside the descent module precluded the cosmonauts from wearing their pressurized suits, and without that protection, the men died where they sat.

Following this sad turn of events, the Soviets fired the Salyut 1's propulsion system for the last time on October 11, 1971, and allowed the space station's orbit to decay until the Salyut 1 incinerated in Earth's atmosphere. Later Salyut stations and missions were unsuccessful or short-lived.

On May 14, 1973, the United States National Aeronautics and Space Administration (NASA) launched its version of a space station with the 36-meter-long Skylab. The station held an orbital workshop, airlock module, multiple docking adapter, and the Apollo Telescope mount. Despite some initial problems, which began with the loss of a meteoroid shield just 63 seconds after liftoff, the Skylab soon became functional. The initial crew to visit the station launched on May 25, 1973, for a 28-day stay. Two subsequent crews launched on July 28 and November 16, 1973, for missions of 59 and 84 days, respectively. After the manned missions, NASA conducted engineering tests of the station from Earth to learn more about long-term space flight and about the initial problems the station faced. Unexpectedly high solar activity ultimately affected the station's orbiting altitude, and on July 11, 1979, the station succumbed to Earth's gravity and collided with the Earth's surface over portions of the Indian Ocean and western Australia.

The next major space station effort on the part of the Soviet Union came with Mir, meaning "peace" or "world." Launched on February 20, 1986, the 20-ton Mir is similar to the Salyut series of space stations, but uses some of the interior area previously occupied by experimental equipment to create small, private crew cabins and a gymnasium. The Mir also has four docking ports for the attachment of scientific and experimental modules. The first cosmonaut crew to Mir spent 125 days in space. The station extended that record with its second mission, which brought two cosmonauts for the station. One stayed on board for six months, while the other spent 326 days in orbit.

In June 1995 the Mir was involved in another milestone when the U.S. space shuttle Atlantis docked with the station. A string of U.S.Russian missions followed, ending with the return in June 1998 of the last American mission to Mir.

The Mir experienced a variety of problems that grew in number and severity through the years, including fires in 1994 and 1997. The final manned mission was planned for spring 2000, followed by the station's demise.

Plans for a new space station became official in 1994 when the United States Congress approved the International Space Station. Hailed by NASA as "the largest international scientific and technological endeavor ever undertaken," the joint effort includes contributions from the United States, Russia, Canada, Japan, Brazil, and the 11 nations of the European Space Agency. In 1995 NASA estimated the station would be up and running by 1998. Due primarily to economic and political turmoil in the nations involved, assembly didn't begin until 1998. Estimates in late 1999 pushed back the completion date for the ISS to 2004. Upon completion, the station will measure about 100 meters long and weigh some 475 tons.

Impact

If humans are to one day explore the solar system, much less the universe, we must learn how to survive extended periods beyond Earth's natural life-support systems and in microgravity conditions. In 1971 the first manned space station, Salyut 1, opened the doors to long-term space travel by allowing its first visiting cosmonauts to live in space for more than three weeks. Although the mission ultimately ended in tragedy for the three cosmonauts, the station itself was a success.

With a scientific payload of more than 2,640 pounds, the station carried two telescopes to gather astronomical information, and a number of cameras for studies of the Earth and the cosmos. Primarily, the Salyut crew conducted medical experiments relating to the ability of the human body to survive the rigors of long-term space travel. The cosmonauts also adopted a physical regimen to counter the deteriorating effects of the microgravity environment on their bones and muscles.

In addition, cosmonauts on that first manned space station performed a variety of plant and animal experiments, such as the hatching of frog eggs into tadpoles, and the growth of insects and small plants.

Like the Salyut missions, the Skylab and Mir station missions had a focus on medical experimentation to determine the effects of weightlessness on the human body. American astronaut Jerry Linenger, M.D., summed up the impact of microgravity during a press conference after his return from a 1997 mission aboard the Mir space station. He explained that the bones begin losing calcium and mass in a weightless environment. "You're just floating in space. Medically it's worse than bed rest." He added that bone loss would pose a perpetual problem during long periods in space. The Mir program confirmed that bone loss in microgravity continues at a rate of 1.2 percent in the lower hip and spine per month. Linenger reported that he experienced about 12 percent hip/lower spine bone mass loss while aboard Mir, and after a year back on Earth he was still down by 3-4 percent despite a rigorous exercise routine.

In addition to the medical experiments, astronauts aboard Skylab took nearly 175,000 pictures of Earth and the Sun with its telescopes and specially designed cameras, providing information for a variety of solar studies and investigations of Earth resources and weather patterns. Its solar studies produced images of coronal holes and observations of the comet Kohoutek, which neared Earth during the third Skylab mission.

On the non-human, biological side, cosmonauts and astronauts aboard the Mir were able to grow plants from seeds and harvest the secondgeneration seeds. These techniques—essentially farming in space—are a necessity for long-term space flights that require the crew to grow their own food. Technologically, each success—and failure—aboard the Mir station provided abundant information about space station design and systems. For example, the many successful dockings of spacecraft with the station helped designers understand the intricacies of joining two space vehicles; the 1977 fire led to a modification of the station's software so that the ventilation system, which fanned the fire, could be shut down with one command.

The International Space Station is the next step in the space station endeavor. From the amount of interior area that astronauts and cosmonauts will need to live and work, to exercise equipment that will help them prevent microgravity-induced bone loss, to new fail-safe systems to protect the crew from the unexpected, the ISS will draw on the histories of the Salyut, Skylab and Mir to create a more advanced facility for long-term space habitation.

LESLIE A. MERTZ