International Space Station
International Space Station
The International Space Station (ISS), formally designated International Space Station Alpha, is a habitable (normally manned) orbital facility that has been under construction since 1998 and is scheduled for completion (as of October 2006) in 2010. About 40 assembly and utilization flights (in total) by the United States space shuttle fleet are required to assemble the ISS. In addition, the Russian space program will fly other necessary construction flights, along with Japanese and
ESA flights to add experimental equipment, fuel, consumable, and other necessary materials to ISS. The space station is a joint project of the United States (National Space and Aeronautics Administration, NASA), Russia (Russian Federal Space Agency, RKA), Japan (Japan Aerospace Exploration Agency, JAXA), Canada (Canadian Space Agency, CSA), and Europe (European Space Agency, ESA). (Brazil also participates through NASA, while Italy participates through ESA.) As of October 2006, participants from twelve countries have worked onboard ISS. When finished, it will contain about four times as much working space as the former Russian space station Mir (1986–2001), the former record holder, and will have a mass of about 881,800 lb (400,000 kg) and a pressurized volume of about 35,300 cu ft (1,000 cu m). The ISS orbits at an average altitude of 220 mi (360 km) and at an average speed of 17,200 mph (27,685 km/h).
A number of science experiments are to be conducted aboard the ISS in such fields as health effects of radiation, molecular and cell biology, earth science, fluid dynamics, astronomy, combustion physics, and crystal growth.
History and structure
The ISS was originally proposed by United States President Ronald Reagan (1911–2004) in 1984, and was slated to cost $8 billion. Originally, thirty-six U.S. shuttle flights plus nine Russian rocket launches were required for ISS construction. However, as of October 2006, fewer flights will be needed due to cutbacks on the number of sections to be installed on the structure. The project is about five years behind schedule due primarily to the two U.S. space shuttle disasters in January 1986 (Challenger ) and February 2003 (Columbia ). Since the 2003 loss of Columbia twelve construction flights will be used to finish the building of ISS. Today there are 15 major partners in the ISS effort, including the United States, Russia, Japan, Canada, and 11 of the member states of the European Space Agency. The U.S., through its National Aeronautics and Space Administration (NASA), is the largest single contributor, bearing most of the cost of building, launching, and operating ISS for at least a decade.
Assembly of the ISS commenced in 1998 with launch of the Russian control module Zarya on a proton rocket from Kazahkstan. The U.S. module Unity Node, a connecting segment, was carried into space on the shuttle Endeavor later in 1998. This unit is primarily a docking hub to which other sections join. In 2000, another Proton rocket lofted the Russian service module Zvezda, the main Russian contribution to the ISS. Zvezda provided living quarters and life support during the early phases of the ISS’s growth; it also provides steering rockets to control the ISS’s attitude (orientation in space) and to re-boost it to higher altitudes as its orbit decays due to friction with high-altitude traces of the Earth’s atmosphere.
The ISS is powered by photovoltaic electricity. The first of its four large solar arrays (112 by 39 ft [34.2 by 11.9 m]) was added in 2000. When completed, the ISS will receive about 260 kilowatts of power (peak) from an acre of sun-tracking solar panels. An energy-storage subsystem consisting of six large nickel-hydrogen (Ni-H2) batteries supplies electrical power to the ISS during its passage through Earth’s shadow, which lasts about 45 out of every 90 minutes.
In 2001, the U.S. laboratory module Destiny, the largest and most elaborate of the ISS components, was added using the robot arm of the space shuttle Atlantis. The United States lab module contains 13 equipment racks, on which various scientific experiments will be mounted, and a 20-in (0.5-m) window set in the Earthside wall.
Smaller components were added piecemeal in 2002 by several shuttle flights, and in 2001–2002 several Russian flights ferried passengers and supplies. The ISS’s final configuration will contain a European laboratory module, a Japanese laboratory module, three Russian laboratory modules, a Canadian robot arm to assist in assembly and maintenance, exterior racks for experiments requiring direct exposure to space, and an emergency Crew Return Vehicle on standby. The shuttle has been continuously inhabited since November 2, 2000, and under normal circumstances houses a full crew of six.
The ISS is intended to serve as a platform for the performance of scientific experiments that can only be carried out in space. The presence of a crew allows more complex experiments to be performed with simpler equipment than would be possible using purely robotic space vehicles. On the other hand, human beings require much complex gear to survive in space. Further, the ISS is not a particularly efficient platform for astronomical experiments, as it is vulnerable to vibrations, and experiments that merely require a vacuum can be performed economically in vacuum chambers on Earth. Yet, the ISS does offer something that cannot be obtained for more than a few seconds at a time on earth: weightlessness, or, more precisely (since the components of the ISS itself create a slight gravitational field), microgravity.
Unlike traditional science-fiction space stations, the ISS does not rotate in order to provide a centrifugal equivalent of gravity to its inhabitants. Such an arrangement would require a much more expensive structure due to the stresses imposed by rotation; observational science experiments that need to point steadily at one part of the sky would be difficult to operate on a rapidly rotating platform; and rotation would destroy the very microgravitational conditions that make the ISS a unique place to conduct science.
Several of the experiments that have exploited (or will exploit) microgravity are the following:
- Dendrite formation in solidifying metals. When metals solidify they tend, like snowflakes, to form branching or treelike crystalline structures termed dendrites (from the Greek word dendrites, meaning pertaining to a tree). Observing the growth of metallic dendrites that are not deformed by Earth’s gravity should help improve mathematical models of dendrite formation, which in turn may help in the design of stronger and more durable alloys.
- Bone deterioration. As previous experience with long-term habitation of space has shown, persons living in weightlessness lose about 1% of their bone mass per month, even when performing bone-stressing exercises. Generations of small animals raised in space will enable biologists to study the effect of microgravity on genetic mechanisms of bone growth and resorbtion. Understanding these mechanisms may someday make long space voyages (e.g., to Mars) medically feasible.
- Atomic clock. A French experiment will use micro-gravity to improve the accuracy of an atomic clock by a factor of ten by observing oscillations of cesium atoms in free fall.
- Commercial research. Between 30 and 40% of the United States lab module resources are reserved for use by private corporations, who will pay for access to microgravity research conditions. A slightly lower percentage of lab resources are reserved for commercial buyers in the European laboratory module. However, few corporations have yet purchased lab time on the ISS.
The ISS is enthusiastically supported by many people who are interested in space travel for its own sake and by those scientists who hope to fly their own experiments on the platform. However, it has long been heavily criticized by a majority of the scientific community for delivering too little science for the dollar. In other words, it diverts money from other research. Some scientists argue that the bulk of the research planned for the ISS addresses technical questions that are peripheral, rather than fundamental. For example, Science, the journal of the American Association for the Advancement of Science, complained in 1998 that the ISS’s “greatest impact will be felt in the small community already studying problems related to space flight—a vital research area only if we assume that increasing numbers of people will someday travel, or even live, outside of normal Earth gravity.” In other words, the ISS is an ultimately romantic project that puts astronauts in space in order to figure out how to put more astronauts in space.
The claim that the ISS has little to offer science was boosted by Russia’s conveyance to the ISS of two private space tourists—officially designated Space Flight Participants—in 2001 and 2002, over loud protests from other ISS participant nations. Two wealthy men, one American and the other South African, paid $20 million apiece to the cash-strapped Russian government in exchange for a trip to the ISS. As of 2006, four space tourists have gone to the ISS via Russian supply missions, at a cost of $20 million each.
Even before the loss of the space shuttle Columbia in February 2003, funding for completion of the ISS was in doubt. Both the United States Congress and the governments of the European Union have long been skeptical of the ISS’s costs, and NASA was under such political pressure that it admitted it could not guarantee that the station will ever be grown beyond the “core complete” stage, with long-term living quarters for only three astronauts. Three astronauts, however, are not enough to tend the scores of experiments for which the ISS’s racks have room, so if the ISS is not expanded much of the science potential already constructed will go to waste. Critics of the ISS argued that continued support for the ISS amounted to throwing good money after bad; supporters of the ISS counter-argued that ISS research is essential for make an eventual trip to Mars and that human space-travel projects generate valuable technological spinoffs.
The Columbia disaster of early 2003 has, has delayed the progression of ISS by numerous months. Although Russian rockets have supplied many of the ISS’s needs and ferried astronauts back and forth to it, only the space shuttle’s cargo hold is large enough to carry many of the components planned for the ISS. Another, more urgent factor is that the ISS loses orbital altitude steadily due to friction with the outer fringes of the Earth’s atmosphere. Small rockets attached to the station regularly restore its altitude. The fuel for these rockets has been delivered via space shuttle, but after the Columbia disaster, minimum needed deliveries of fuel has been provided by the Russians until the United States resumed fuel deliveries in 2006.
As of 2006, about 80% of the original hardware for the ISS will still be added to ISS. Between 2006 and 2010, 16 shuttle flights by the space shuttle fleet will deliver hardware to ISS. Two flights have already flown: Discovery (STS-114) launched on July 26, 2005, with the External Stowage Platform onboard, and Atlantis (STS-115) launched on September 9, 2006 with the P3/P4 Truss-Solar arrays onboard. STS-121 (Discovery ) also flew on July 4, 2006, but did not send any assembly structures to ISS.
If all goes on schedule, in 2007, the following will be delivered to the ISS: Node 2 (built by Italy) to provide air, electrical power, water, and other life support systems; and Columbus Laboratory Module (ESA) to provide science equipment such as the Fluid Science Laboratory, Biolab, and European Drawer Rack. In 2008: Multipurpose Laboratory Module (Russia) to provide Russian science equipment; and Japanese Experiment Module (Japan, on three shuttle flights) to provide two pressurized sections and one exposed facility. In 2009 and 2010: Node 3 and Cupola (Italy, may be cancelled) to provide storage space; and unpressurized elements to support solar arrays.
It is very difficult to pinpoint an exact figure for the cost of ISS because so many countries are contributing to the project. In addition, the annual U.S./NASA budget for the space shuttle program is not included in the cost of ISS, even though much of its expense involves serving the space station. However, the most quoted figure for all of the participants of the ISS, as of 2006, stands at about $100 billion. The ISS budget for NASA is listed as $25.6 billion for 1994 through 2005; $1.7 billion and $1.8 billion for 2005 and 2006, respectively; and a rising budget from 2007 to 2010, with an estimated budget in 2010 of $2.3 billion. The budget is expected to level off after 2010, with an expected end of the project in 2016.
The future of the ISS is highly dependent on the health of the space shuttle fleet. No other country except the United States can accomplish all the assembly flights necessary to complete the station. If NASA suffers another disaster or a serious problem with the shuttles, then the completion of the ISS is doubtful at best. NASA resumed flights on July 26, 2005, with the STS-114 mission of Discovery. The mission was successful; however, foam was again shed from the external tank. NASA officials grounded the fleet until the problem was identified and resolved. NASA resumed shuttle flights in July 2006. With two successful flights to the ISS, NASA is hopeful that the space station can be completed by 2010. NASA expects to retire the space shuttle fleet in 2010 and replace it with Orion, an Apollo-type vehicle that will take humans to the moon and Mars beginning in 2015.
See also Gravity and gravitation; Spacecraft, manned.
Launius, Roger D. Space Stations: Base Camps to the Stars. Washington, DC: Smithsonian Books, 2003.
Rau, Dana Meachen. The International Space Station. Minneapolis, MN: Compass Point Books, 2005.
Lawler, Andrew, “Can Space Station Science Be Fixed?” Science. 5572 (May 24, 2002): 1387–1389.
Lawler, Andrew, “Space Station Research: Bigger Is Better for Science, Says Report.” Science. 5580 (July 19, 2002, 2002): 316–317.
Revkin, Andrew. “And Now, the Space Station: Grieving, Imperiled.” New York Times. February 4, 2003.
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National Aeronautics and Space Administration. “Space Station.” <http://www.nasa.gov/mission_pages/station/main/index.html> (accessed October 13, 2006).
International Space Station
International Space Station
November 20, 1998
The International Space Station (ISS), under construction since 1998, is the largest international scientific partnership in history. The project involves seventeen countries: the United States, the eleven member nations of the European Space Agency, Canada, Japan, Russia, Italy, and Brazil. When the ISS is completed, astronauts will have assembled a total of one hundred separate parts during forty-five missions while the station orbits 240 miles (384 kilometers) above Earth. The ISS will eventually consist of several modules, and as many as seven crew members will live on board, conducting scientific experiments and space research. By 2004 eight crews had already stayed on the ISS for months at a time. Construction had been postponed in 2003, however, as a result of the Columbia space shuttle disaster, and the future of the ISS remained uncertain. (A space shuttle is a craft that transports people and cargo between Earth and space.)
"I think … having a space station is somewhat an evolutionary step in where we are going in this next millennium."
William M. "Bill" Shepherd, Space Station Commander Expedition 1
Soviets launch first space stations
Although the former Soviet Union built the first space stations, which ultimately led to the development of the ISS, the
actual concept has roots in the nineteenth century. The idea of a space station has been traced back to "The Brick Moon: From the Papers of Captain Frederic Ingham," a story by author Edward Everett Hale (1822–1909) published in the Atlantic Monthly magazine (1869–70). "The Brick Moon" describes how Captain Frederic Ingham and his former college friends build an artificial Moon made of brick. According to Elizabeth Paulhaus, writer of the online article "Brick Moon Rising."
The first known mention of the term "space station" was made by the German rocket engineer Hermann Oberth (1894–1989; see entry) in 1923. He envisioned a wheel-like vehicle that would orbit Earth and provide a launching place for trips to the Moon and Mars. About two decades later the German-born American rocket engineer Wernher von Braun (1912–1977; see entry) proposed a more detailed concept of a space station in a series of articles in Collier's magazine. He described a giant vehicle, 250 feet (762 meters) in diameter, that would spin to create its own gravity as it orbited 1,000 miles (1,609 kilometers) above Earth.
The Soviets launched the world's first space station, Salyut 1, in 1971, during a time of intense competition between the Soviet Union and the United States. Since World War II (1939–45) the two superpowers had been engaged in a period of hostile relations known as the Cold War (1945–91), which involved not only a race for military superiority but also a race for dominance in space. In 1957 the Soviets had launched Sputnik 1, the first artificial satellite (an object that orbits in space), sending shock waves through American society. Sputnik 1 was a sign that the Soviet Union was moving ahead in the Cold War. The next year the United States responded by creating the National Aeronautics and Space Administration (NASA)—and the space race began.
In April 1961 the Soviets stunned the world again by achieving the first manned space flight when cosmonaut (astronaut) Yuri Gagarin (1934–1968; see entry) made a nearly complete orbit of Earth. The following month U.S. astronaut Alan Shepard (1923–1998; see box in John Glenn entry) made a brief but successful trip into orbit. Two years later Soviet cosmonaut Valentina Tereshkova (1937–; see entry) became the first woman in space. Then, in the early 1960s, President John F. Kennedy (1917–1963; served 1961–63) publicly pledged to put an American on the Moon by the end of the decade (see Christopher Kraft [1924–] entry). In 1969, U.S. astronauts Neil Armstrong (1930–; see entry) and Buzz Aldrin (1930–; see entry) accomplished that goal by stepping onto the surface of the Moon.
Mir: first permanent space station
By the 1970s the United States lacked funding for further Moon exploration. The Soviet Union was in a similar situation and therefore never attempted a Moon flight. Instead the Soviets focused on the Salyut program, launching seven Salyut space stations between 1971 and 1982. The United States put the Skylab space station into orbit in 1973, but it remained in space for only one year and was visited by three crews of astronauts. Soviet cosmonauts regularly traveled to the Salyuts, but they did not stay for long periods of time because the space stations did not have adequate living accommodations. Improving upon the Salyut design, the Soviets built Mir, the first permanent residence in space, which was launched in 1986.
Mir provided valuable information about building, maintaining, and living on a space station. Remaining in orbit for more than fifteen years, until 2001, it was officially taken out of service in 1999. During that time astronauts conducted nearly 16,500 experiments, primarily on how humans adapt to long-term space flight. From 1986 until 1999 the space station was almost continually occupied by a total of one hundred cosmonauts and astronauts. Among them were seven NASA astronauts, a Japanese journalist, a British candy maker, and visitors from other countries that did not have their own space programs. In 1995 Russian cosmonaut Valery Polyakov (1942–) set the record for the longest mission aboard Mir, having stayed 438 days. The same year American astronaut Shannon Lucid (1943–; see entry) set the record for a non-Russian, on a mission that lasted 188 days, 4 hours and 14 seconds.
Lucid's record was broken in 1999 by French astronaut Jean-Pierre Haigneré (see box in Claudie Haigneré entry), when he stayed nearly 189 complete days. Haigneré was also a member of the last crew to visit Mir. Before returning to Earth the crew left the space station in a standby mode, with no occupants onboard. When Russia took Mir out of service in 2001, most of the spacecraft burned up over the Pacific Ocean. The remaining remnants of the space station crashed into the Pacific in 2004.
United States and Russia strike a deal
Mir became an international effort, eventually providing a model for the ISS. Before the first two components of the ISS were launched in 1998, however, the United States had attempted to develop its own space station. In 1984 President Ronald Reagan (1911–2004; served 1981–89) provided funding to NASA for development of a space station to be named Freedom. By 1990 cost overruns and poor management had forced NASA to scale back its plans and to design a new space station, the Alpha. Confronted with continuing financial problems, NASA approached Russian officials in 1993 about collaborating on a space station that would merge the Alpha with a second version of Mir. Russia was running out of money to build a Mir 2 that would replace the retired Mir, so a deal was struck. Thus the idea for an international space station was born, and initial on-ground construction began the following year.
ISS is built in space
The ISS is being assembled in three phases, which involve shuttle missions with specific goals, such as delivering and assembling parts, transporting crews, delivering cargo and supplies, and maintaining and servicing the station. A total of twenty-eight missions had been completed by 2004. Selected highlights of the three construction phases are described below.
Phase 1 (1994–98). During the first phase the first two modules and various other elements were constructed for assembly in space. A total of seven U.S. astronauts also gained experience with living in space by spending twenty-seven months aboard the Mir.
Phase 2 (1999–2000). The second phase involved initial in-orbit construction by crews from Russia and the United States. On November 20, 1998, Russia lifted the first component, the cargo block Zarya (Sunrise), into orbit on a Proton
Working on the ISS
Upon completion the ISS will weigh one million pounds and consist of several modules, which astronauts assemble while walking in space. The main components are a port for a Soyuz rescue craft (Soyuz is a Russian space shuttle), a Russian service module, a cargo block, a NASA docking module, a U.S. habitat (living space) module, a U.S. laboratory module, European and Japanese modules for scientific experiments, and a docking port for a U.S. space shuttle. Attached to the modules are trusses (leg-like structures), which will be as long as a football field. The trusses support solar panels (devices for capturing radiation from the Sun), which provide energy for powering the station and scientific experiments. The energy is stored in radiators mounted on the trusses. Communications equipment is also installed on the trusses.
Astronauts receive extensive training in performing extravehicular activities (activities outside a space vehicle). More commonly known as spacewalks, extravehicular trips allow astronauts to work on the ISS. During a spacewalk an astronaut remains connected to the station by means of a device on his or her spacesuit, which is attached to a joint airlock module. The joint airlock module consists of two sections—a crew lock and an equipment lock. An astronaut hooks the device on the spacesuit to the crew lock when exiting the station or while spending extended periods of time outside the station. The equipment lock is used for storing gear.
A spacesuit is adjustable so it will fit different crew members. It is equipped with special features such as gloves that allow free movement of the hands, a radio that permits five people to talk with one another at the same time, and heating and cooling systems. Floodlights and spotlights are mounted on the astronaut's helmet, and the astronaut carries a jet-pack life jacket to be used if he or she is accidentally disconnected from the space station. Astronauts also work with robotic arms to assist them in maneuvering large components and in moving around work areas. While living and working on the ISS, crews must keep track of more than fifty thousand items. To facilitate this process, an electronic tag—roughly one-fourth the size of a postage stamp—is attached to each item. Astronauts read the tags with a solar-powered infrared transmitter, which can scan fifteen thousand tags per minute at a distance of up to 40 feet (12 meters).
rocket. On December 4, 1998, the U.S. space shuttle Endeavour transported the second component, the Unity node, which is a docking hub where major sections of the ISS are locked together. During this mission the Endeavour crew, which included American astronaut Ellen Ochoa (1958–; see entry),
conducted spacewalks and attached the Unity to the Zarya. The third component, the Russian-built service module Zvedza (Star), was launched on July 12, 2000. It provided initial living quarters and life support systems.
The first ISS expeditionary crew (astronauts and cosmonauts who live on the space station) was launched aboard a Soyuz capsule on October 31, 2000. The expedition commander was U.S. astronaut William M. "Bill" Shepherd (1949–); the Soyuz commander was Russian cosmonaut Yuri Gidzenko (1962–); and the flight engineer was Russian cosmonaut Sergei Krikalev (1958–). With their four-month mission the crew began living aboard the ISS. An Endeavour crew visited the ISS in December 2000 to attach a truss structure, on which they installed solar panels, radiators, and communications systems. When the solar panels were installed, the ISS became the third-brightest object in the night sky.
Phase 3 (2001–06). According to the original plan, construction of the ISS is to be completed during the third phase. A considerable amount of work was accomplished from February 2001 until October 2003. Seven more expeditionary crews lived on the station, assembling main modules and other elements. The U.S. Destiny laboratory was attached to the Unity, adding facilities for scientific research on near-zero gravity conditions in space. The Italian-made Leonardo multipurpose module was installed to provide "moving vans" that carry equipment, supplies, and experiments between the station and a shuttle. The Russian Pirs (Pier) docking port was added, a Canadian-made robotic arm was installed for use in future construction projects, and work continued on the complex truss system.
During this period three Soyuz "taxi flights" visited the ISS to exchange the old Soyuz with a new one. This means that the taxi crew left the capsule they arrived in at the space station, then returned to Earth in the old capsule. In October 2001, French astronaut Claudie Haigneré (1957–; see entry) arrived with the third taxi crew aboard the Soyuz vehicle Andromede. On this flight she became the first woman to visit the ISS and the first non-Russian woman to serve as a Soyuz flight engineer.
Columbia tragedy causes delay
Further construction on the ISS was delayed after the space shuttle Columbia accident. On February 1, 2003, the Columbia broke apart over the western United States while returning to Earth from a visit to the ISS (see Challenger Crew entry). All seven crew members were killed as pieces of the descending craft fell from the sky. The day after the incident NASA administrator Sean O'Keefe (1956–) organized the Columbia Accident Investigation Board (CAIB). On August 26 the CAIB issued a final report. The most immediate cause of the disintegration was a piece of insulating foam that had separated from the shuttle's left wing during takeoff. The missing foam left a hole through which leaking gas was ignited by the intense heat of the rocket that propelled the Columbia.
The board also found that the Columbia was not properly equipped for its mission to the ISS. Built earlier than other U.S. shuttles—the Columbia was the first shuttle to leave Earth orbit—the vehicle had been used primarily for scientific missions and for servicing the Hubble Space Telescope (see entry). On the flight to the ISS it was required to carry larger cargo, which the crew had difficulty handling because the Columbia did not have a space station docking system. The CAIB report concluded that the Columbia accident was caused in large part by deficiencies within NASA and by a lack of government oversight. The report stated that shuttle flights were becoming increasingly dangerous and that a minimum number should be flown only when necessary. Completion of the ISS was consequently postponed while NASA studied space shuttle safety issues.
For More Information
Bond, Peter. The Continuing Story of the International Space Station. New York: Springer-Verlag, 2002.
Launius, Roger D. D. Space Stations: Base Camps to the Stars. Washington, DC: Smithsonian Institution Press, 2003.
Hanson, Torbjorn. "Deep Space 1999." Boys' Life (June 1999): p. 28.
Scott, Phil. "Eye on the Junk: Space Station Noises Renew Worry about Orbital Debris." Scientific American (May 3, 2004): p. 27.
Sietzen, Frank Jr. "A New Vision for Space." Astronomy (May 2004): pp. 48+.
"Human Spaceflight." NASA.http://www.spaceflight.nasa.gov/station/ (accessed on June 25, 2004).
"International Space Station." Discovery.com.http://www.discovery.com/stories/science/iss/iss.html (accessed on June 24, 2004).
Paulhus, Elizabeth. "Brick Moon Rising." International Space Station Challenge.http://voyager.cet.edu/iss/cafe/articles/brickmoonrising.asp (accessed on June 25, 2004).
"Where Is the International Space Station?" NASA.http://www.science.nasa.gov/temp/StationLoc.html (accessed on June 25, 2004).
Super Structures of the World: International Space Station—Cities in Space. Unapix/Ardustry, 2000 (Video).
International Space Station
International Space Station
There have long been dreams of a permanently inhabited base or station in space. In 1957 it first became possible to put human-made objects into orbit around Earth. But while both the United States and the Soviet Union raced to send a man to the Moon in the 1960s, the goal of a space station in orbit was secondary. It was after the United States won that "space race" in 1969 that both spacefaring countries sought new directions for their human spaceflight programs.
Previous Space Stations
Shortly before the National Aeronautics and Space Administration (NASA) launched the first Moon mission, the agency began focused design work on America's first orbiting laboratory—Skylab—a converted Saturn Moon rocket stage. Only 36 meters (117 feet) long, it did not rotate to create the artificial gravity that physiologists of two decades earlier believed would be required for humans to live in space. Skylab was launched in May 1973 and occupied intermittently over the following five and a half months by three successive three-person crews. Since it was already known that astronauts could survive weightlessness, answering other questions became paramount. There were unlimited questions about how chemistry, physics, biology, and engineering principles worked without gravity, along with a unique vantage for observations of the Sun and Earth. In February 1974, after only 171 days of occupancy, this successful project was ended. NASA had been given a higher priority manned spaceflight project by President Richard M. Nixon: build a reusable spaceship—the space shuttle. Skylab was to be the last U.S. space station project for a decade.
Soon after Apollo 11 ended the Moon race in 1969, the Soviet Union turned its efforts to short-term Earth-orbiting laboratories. The Soviets named their first generation space station Salyut. In April 1971 Salyut 1 was orbited. Two to three cosmonauts, launched to the station in Soyuz spacecraft, lived for weeks in the cylindrical lab/home with a volume half that of the inside of a school bus. The Russians orbited seven successive space stations over a period of eleven years and conducted thirty-eight crewed missions onboard. They were mostly successful. These early Soviet stations were occupied intermittently for increasingly long periods of up to almost eight months. Salyut 7 was still in orbit when a new Soviet space station project began in February 1986 with the launch of the Mir core module.
Mir was the first permanently crewed station designed as an assembly, or complex, of specialized research modules. The five modules were added one at a time through April 1996. Even while beginning the assembly and operation of Mir, the Soviets were planning another Mir-type station—a plan revised because of developments both at home and in the United States.
The Modern Space Station Project
In his State of the Union address before a joint session of the U.S. Congress on January 25, 1984, President Ronald Reagan directed NASA "to develop a permanently manned space station and to do it within a decade." He went on to say that "NASA will invite other countries to participate." So began the International Space Station (ISS) project and, indirectly, the coalescing of Russian and American space station projects.
NASA had pressed the White House and Congress for a permanent space station project since the successful Space Transportation System (space shuttle) flight program began in 1981. Preliminary design studies were already underway when the president made his announcement. Within weeks NASA invited other countries to join the project. Interest was already high at the European Space Agency (ESA), the intergovernmental agency for eleven European countries, with whom the United States had a decade of experience through ESA's contributions to the space shuttle program. The Canadian Space Agency and the National Space Development Agency of Japan were also interested in participating.
There was basic agreement among all space agencies as well as the Congress (now a virtual partner in its role as authorizer of NASA activities and appropriator of funds) that the station was to be modular in construction. The space shuttle was to be the major launcher of components and crew.
In early 1984, the space station concept was an architecture of three elements: a crewed complex with laboratories, a co-orbiting automated science satellite or platform, and another platform in polar orbit. The reference design for the central complex was called the "Power Tower," reflecting its resemblance to that structure. But when technical evaluation revealed a less than adequate microgravity environment for the laboratories, another concept called "Dual-Keel" became the baseline design in 1985. The large squared structure of trusses and beams with the occupied modules at the center of gravity gave this configuration its name. Outrigger-like trusses secured the solar arrays . ESA negotiated a preliminary agreement to contribute a pressurized laboratory module and the polar platform; Japan agreed to provide another laboratory and a cargo carrying module; and Canada would provide a mobile robotic system that would do work along the external structure. By the end of 1986 the space shuttle Challenger accident had enhanced the concern for crew safety, leading to such changes as reduced shuttle flight rates and fewer space walks for construction. A "lifeboat" for emergency crew return was also added to the plans. These changes forced a reduction in size.
In 1988, the international partners signed formal cooperation documents for the space station project, which they agreed would be named "Freedom." Each partner's contribution would be paid for by that partner. In this period the cost of the U.S. portion—the largest share of the project—began to draw the attention of NASA and the U.S. Congress. The initial cost estimate in 1984, just for design, development of new technical hardware and software, manufacture, and preparation for launch, was $8 billion. Five years later the cost estimate, through "assembly complete," had grown to $30 billion. Subsequent cost-containment actions included the indefinite delaying of some structure and power generation features and the dropping of the polar platform from the station project.
As design work progressed fitfully at NASA's design centers and U.S. contractor companies tabulated further increases in estimated total cost, the activities that "Freedom" could support were under almost constant review and change. By 1993 the reductions in station capability compared to its estimated cost forced the cancellation of the "Freedom" design. Very little hardware had been built. As a new design concept was being developed, President Bill Clinton announced that the new space station project would include not only the previous international partners but Russia as well.
Even as the space station Mir continued in operation in space the Soviet government fell in the early 1990s. Soviet plans for a follow-on to Mir were evaporating. Russia joined the U.S. partnership for a new design that was named International Space Station Alpha (ISSA). The next-generation Russian space station elements would be installed as part of the Alpha station, and American astronauts would join cosmonauts onboard the Mir for seven long-duration missions in the mid-1990s. The Russians got their next-generation space station when their collapsing economy could not afford to fund the effort by itself. The United States got early long-duration spaceflight experience—up to six months at a stretch—for its astronauts and ground controllers. Russian design and operational spaceflight experience also became available for a project at least as complex as the Apollo Moon landings.
In late 1993, detailed design of ISSA, later shortened to ISS, was begun, drawing upon 75 percent of the "Freedom" design. This space station looks like a Tinkertoy assembly of one 88-meter-long (290-foot-long) beam, with four wing-like power panels at each end, and a collection of centrally mounted cylinders—the modules. If it could be assembled on the ground it would cover an area as large as two football fields. Its design is refined to provide the lowest possible gravitational disturbances—microgravity—within its four central laboratory modules, while generating power from sunlight that was greater than the energy used in ten average American homes. Initially three and eventually seven international astronauts could work on-board for up to six months before exchanging with the next crew. The volume of space where they lived and worked was about the size of three two-bedroom American homes.
The first module of the ISS was launched by Russia in November 1998. It served as the core for the two U.S. and one Russian modules that followed. Although Russian funding problems and U.S. equipment problems have caused some delays, in mid-2001 the second expedition of three was installed aboard the station, now once again named "Alpha" by the crews. Biotechnology and human biomedical research is being done in the U.S. laboratory module named "Destiny." As more shuttle flights outfit the laboratory and later the European and Japanese laboratories are docked to ISS, research will progressively increase to include science in fundamental biology and physics, fluid physics, combustion science, materials science, technology development, and the earth and space sciences.
Commercial industries of all sorts are being offered a share of the facilities for work on products and services for Earth. Completed assembly and outfitting of the ISS is planned for around 2005, with an operating life of at least ten years. Overall mission control will still be from Houston, Texas, backed up by Moscow, Russia, and with small staffs for routine operations planning and ground control functions. During the space station's operation as a hybrid science laboratory and industrial park in orbit, researchers will conduct most of their work remotely from desktop control stations in their Earth-bound labs or offices. Following experiment setup by a space station crew member, telescience will lead to great efficiencies, allowing the crew to focus on maintenance and hands-on-required research. The ISS has been a world-class challenge and is becoming a world-class facility for twenty-first century innovations in science, technology, and commerce.
see also International Cooperation (volume 3); International Space Station (volume 1); Ley, Willy (volume 4); Microgravity (volume 2); Mir (volume 3); Skylab (volume 3); Space Shuttle (volume 3); Space Stations of the Future (volume 4).
Charles D. Walker
Hall, Rex, ed. The History of Mir, 1986-2000. London: British Interplanetary Society, 2000.
Mark, Hans. The Space Station: A Personal Journey. Durham, NC: Duke University Press, 1987.
National Aeronautics and Space Administration. The International Space Station Fact Book. Washington, DC: Author, 2000.
Newkirk, Dennis. Almanac of Soviet Manned Space Flight. Houston, TX: Gulf Publishing Company, 1990.
Rumerman, Judy A. U.S. Human Spaceflight: A Record of Achievement, 1961-1998. Washington, DC: National Aeronautics and Space Administration, 2000.
International Space Station. National Aeronautics and Space Administration. <http://spaceflight.nasa.gov/station/index.html>.
Smith, Marcia. NASA's Space Station Program: Evolution and Current Status. Testimony Before the House Science Committee. U.S. Congress. <http://www.house.gov/science/full/apr04/smith.htm>.
Space Station, International
Space station, international
The International Space Station (ISS) is a permanent Earth-orbiting laboratory that will allow humans to perform long-term research in outer space. Led by the United States, the ISS draws upon the scientific and technological resources of sixteen nations. When completed in 2006, it will be the largest and most complex international scientific project in history.
The International Space Station had its beginnings in the cold war rivalry (period of silent conflict and tension) that existed between the United States and the then Soviet Union (also called the U.S.S.R.) from the 1950s to the 1990s. Although the United States was the first to put a man on the Moon (1969), the Soviet Union came to specialize in and dominate the field of long-term human spaceflight. As early as 1971, they successfully launched the world's first orbiting space station (Salyut 1 ) and continued nearly uninterrupted through the 1990s. Where the United States has placed only one space station in orbit (Skylab in 1973) and sent only three crews of three astronauts to live there (none longer than eighty-four days), the Soviet Union gained valuable space station experience by regularly shuttling crews to its three generations of stations. One crew member remained in space for a 438-day tour.
Around the mid-1980s, the United States decided to compete against and try to outdistance the Soviet Union in the space station field, since it felt that a long-term manned presence in space was what its military would need in the future. The United States invited other nations (except the Soviet Union) to participate on what it called Space Station Freedom. When the it collapsed and broke apart in 1991, the former Soviet Union (now called Russia) was eventually invited to join the effort. Since the Russian Space Agency faced severe financial problems (as did all of Russia after the break-up), it accepted help from the United States and eventually agreed to join and lend its vast experience to the creation of a truly international station in space.
In 1993, the United States put forth a detailed long-range ISS plan that included substantial Russian participation as well as the involvement of fourteen other nations. Altogether sixteen countries—Belgium, Brazil, Canada, Denmark, France, Germany, Italy, Japan, the Netherlands, Norway, Russia, Spain, Sweden, Switzerland, the United Kingdom, and the United States—have banded together on a non-military effort so complex and expensive that no one nation could ever consider doing it alone. The program will involve more than 100,000 people in space agencies and contracting companies around the world. It is expected to cost at least $40 billion and take nearly a decade to complete.
The ISS project has lofty goals. It is expected that having long-term, uninterrupted access to outer space will allow investigators to acquire large sets of data in weeks that would have taken years to obtain. The ISS project also plans to conduct medical and industrial experiments that it hopes will result in benefits to all humankind.
ISS systems and size
The ambitious ISS has been likened in difficulty to building a pyramid in the zero gravity or weightlessness of outer space. When completely assembled, the ISS will have a mass of nearly 1 million pounds (454,000 kilograms) and will be about 360 feet (110 meters) across by 290 feet (88
meters) long, making it much wider than the length of a football field. This large scale means that it can provide 46,000 cubic feet (1,300 cubic meters) of pressurized living and working space for a crew of seven scientists and engineers. This amount of usable space is greater than the volume of the passenger cabin and cargo hold of a huge Boeing 747-400 aircraft. This massive structure will get its power from nearly an acre of solar panels spread out on four photovoltaic (pronounced foe-toe-vole-TAY-ik) modules. These solar arrays rotate to always face the Sun and can convert sunlight into electricity that can be stored in batteries. The station will have fifty-two computers controlling its many systems.
The main components of the ISS are the Service Module, which is Russia's first contribution, and then six scientific laboratories (one American, one European Space Agency, one Japanese, and three Russian labs). The other major contributor is Canada, which is providing a 55-foot-long (16.7-meter-long) robotic arm for assembly and other maintenance tasks. The United States also has the responsibility for developing and ultimately operating all the major elements and systems aboard the station. More than forty space flights over five years will be required to deliver these and many other space station components to the orbiting altitude of 250 miles (402 kilometers) above Earth.
Assembly in space
The Russians placed the first major piece of the puzzle—the control module named Zarya—in orbit during November 1998. Following the launch of the American module named Unity during December of that year (which would serve as the connecting passageway between sections), the Russians launched their service module named Zvezda in July 2000. This not only provided life support systems to other elements but also served as early living quarters for the first crew. After more flights to deliver supplies and equipment, the American laboratory module named Destiny was docked with the station during February 2001. This state-of-the-art facility will be the centerpiece of the station. The aluminum lab is 28 feet (8.5 meters) long and 14 feet (4.3 meters) wide and will allow astronauts to work in a year-round shirtsleeve environment. Following the addition of a pressurized laboratory built by the European Space Agency, the robotic arm built by Canada, and a Japanese Experiment Module, the station will have many of its most important working components assembled.
Uses of space research
Since the main goal of the ISS is to conduct long-term scientific research in space, the crews naturally have a great deal of research to perform. Some examples of the type of research conducted are protein crystal studies. It is believed that since zero gravity allows more pure protein crystals to be grown in space than on Earth, analysis of these crystals may lead to the development of new drugs and a better understanding of the fundamental building blocks of life. Growing living cells in zero gravity is also a benefit since they are not distorted by gravity. Astronauts can therefore grow tissue cultures aboard the station that can be used to test new treatments for cancer without risking harm to patients.
Astronauts will also be testing themselves and learning more about the effects of long-term exposure to reduced gravity on humans. Studying how muscles weaken and what changes occur in the heart, arteries, veins, and bones may not only lead to a better understanding of the body's systems, but might help us plan for future long-term human exploration of the solar system.
Flames, fluids, and metals all act differently in zero gravity, and astronauts will be conducting research in what is called Materials Science to try to create better alloys. The nature of space itself will be studied by examining what happens to the exterior of a spacecraft over time. Also of great interest are the physics of forces that are difficult to study when they are subject to the gravity of Earth. New products will regularly be sought after, and there is hope that space may have real commercial potential that might lead to the creation of industry in space.
Lastly, Earth itself will be watched and examined. Studying its forests, oceans, and mountains from space may lead us to better understand the large-scale, long-term changes that take place in our environment. We can also study how badly we are harming our planet with air and water pollution and by the cutting and burning of forests. The ISS will have four large windows designed just for looking at Earth.
The future in space
The assembly in space of such a huge station has begun a new era of hands-on work in space. More spacewalks than ever before will have to be conducted (about 850 hours will be required before the astronauts are finished). Already, Earth orbit has literally become a day-to-day construction site. Once completed, the ISS will be permanently crewed, and the crews will rotate during crew-exchange flights. The outgoing crew will "handover" the station to the incoming crew.
During the first few years, emergencies that require crew evacuation will be handled by always having a Russian Soyuz return capsule onboard. Eventually this will be replaced by an X-38 Crew Return Vehicle that will look more like an airplane (as the space shuttle does) and will function as an all-purpose space pickup truck. Finally, despite the best of plans, there is always the possibility that the space station may not be fully completed due to any number of political, engineering, or financial reasons. Designers therefore have taken this into account and have planned the project so that it can still be fully used despite only limited completion.
[See also Spacecraft, manned ]
International Space Station
International Space Station
The International Space Station (ISS) is a scientific and technological wonder. It is a dream being realized by a multinational partnership. The ISS provides a permanent human presence in space and a symbol of advancement for humankind.* There is great promise and discovery awaiting those who will use the space station.
Just as the global explorers of the fifteenth century circled the globe in their square-sailed schooners in search of riches—gold, spices, fountains of youth, and other precious resources—so too is the space station a wind-jammer plowing the waves of space, exploration the riches it holds. The space station brings together the adventure of fifteenth-century explorers with twenty-first-century technology and industry. The space station is, at its essence, an infrastructure that will facilitate and transmit new knowledge, much like that provided through the virtual world of the Internet. In regard to the space station, the question is: From where will the value of this virtual world come? Or, put in terms of the fifteenth-century explorers, "What is the spice of the twenty-first century in the new frontier of space?"
At this stage, no one can guess what the most valuable and profound findings from space station research will be. Space research done to date, however, does point the way to potential areas of promise that will be further explored on the ISS. The space environment has been used to observe Earth and its ecosphere, explore the universe and the mystery of its origin, and study the effects of space on humans and other biological systems, on fluid flow, and on materials and pharmaceutical production.
The space station creates a state-of-the-art laboratory to explore ourselves and the world. The discoveries we have made to date in space, while significant, are only the foundation for what is to come. Research in microgravity is in its infancy. Throughout the thousands of years that physical phenomena have been observed, including the relatively recent 400 years of documented observations, it has been only in the period since the 1960s that experiments in microgravity of more than a few seconds have been observed; only since the late 1990s has there been a coordinated set of microgravity experiments in space. The most telling indicator is that by the end of 2001 more than half of all microgravity experiments had been conducted since 1998.
History is rife with failed predictions. Nevertheless, perhaps the best way to try to predict the future is to look at the evolution of the past, using history and the current situation as a jumping-off point, while recognizing the challenge in predicting the future. The following represents an attempt to peer into the future, to see what promise lies ahead for the space station by looking at the past and the present.
Previous Advances from Space Activities
In the twentieth century, space exploration had a profound impact on the way we viewed ourselves and the world in which we live. Viewing our planet from space for the first time gave us a unique perspective of Earth as a single, integrated whole. Observations of Earth's atmosphere, land, and oceans have allowed us to better understand our planet as a system and, in doing so, our role in that integrated whole. Many aspects of our lives that are now taken for granted were enabled, at least in part, by investments in space. Whether making a transpacific telephone call, designing with a computer-aided design tool, using a mobile phone, wearing a pacemaker, or going for an MRI, we are using technology that space exploration either developed or improved.
In the early twenty-first century, commercial interests offer a myriad of products and services that either use the environment of space or the results of research performed in microgravity. Just a few examples include:
- Satellite communications: Private companies have operated communications satellites for decades. Today, private interests build, launch, and operate a rapidly expanding telecommunications infrastructure in space. The initial investment in space of the United States helped fuel the information revolution that spurs much of the nation's economy today.
- Earth observation/remote sensing: A growing market for Earth imagery is opening up new commercial opportunities in space. Private interests now sell and buy pictures taken from Earth orbit. Land-use planners, farmers, and environmental preservationists can use the commercially offered imagery to assess urban growth, evaluate soil health, and track deforestation.
- Recombinant human insulin: The Hauptman-Woodward Medical Research Institute, in collaboration with Eli Lilly and Company, has used structural information obtained from crystals grown in space to better understand the nuances of binding between insulin and various drugs. Researchers there are working on designing new drugs that will bind to insulin, improving their use as treatments for diabetic patients.
What all these discoveries have in common is that they use space as a resource for the improvement of human conditions. Efforts aboard the ISS will continue this human spirit of self-improvement and introspection. And the twenty-first century holds even greater promise with the advent of a permanent human presence in space, allowing that same spirit to be a vital link in the exploration process. The space station will maximize its particular assets: prolonged exposure to microgravity and the presence of human experimenters in the research process.
Potential Space Station-Based Research
The ISS will provide a laboratory that can have profound implications on human health issues on Earth. Many of the physiological changes that astronauts experience during long-term flight resemble changes in the human body normally associated with aging on Earth. Bone mass is lost and muscles atrophy , and neither appear to heal normally in space. By studying the changes in astronauts' bodies, scientists might begin to understand more about the aging process. Scientists sponsored by the National Aeronautics and Space Administration are collaborating with the National Institutes of Health in an effort to explore the use of spaceflight as a model for the process of aging. This knowledge may be translated into medical wonders, such as speeding the healing of bones and thereby reducing losses in productivity. By beginning to understand the process by which bones degenerate, scientists might be able to reverse the process and expedite the generation of bone mass.
The microgravity environment offers the opportunity to remove a fundamental physical property—gravity—in the study of fluid flow, material growth, and other phenomena. The impacts on combustion, chemistry, biotechnology, and material development are promising and exciting. The combustion process, a complex reaction involving chemical, physical, and thermal properties, is at the core of modern civilization, providing over 85 percent of the world's energy needs. By studying this process on the ISS, commercial enterprises could realize significant savings by introducing new-found efficiencies.
Researchers have found that microgravity provides them with new tools to address two fundamental aspects of biotechnology: the growth of high-quality crystals for the study of proteins and the growth of three-dimensional tissue samples in laboratory cultures. On Earth, gravity distorts the shape of crystalline structures, while tissue cultures fail to take on their full three-dimensional structure.
The microgravity environment aboard the ISS will therefore provide a unique location for biotechnology research, especially in the fields of protein crystal growth and cell/tissue culturing. Protein crystals produced in space for drug research are superior to crystals that can be grown on Earth. Previous research performed on space-grown crystals has already increased knowledge about such diseases as AIDS, emphysema, influenza, and diabetes. With help from space-based research, pharmaceutical companies are testing new drugs for future markets.
In addition to these scientific findings, the ISS serves as a real-world test of the value of continuous human presence in space. There are already companies focused on space tourism and the desire to capitalize on the human presence in space. A myriad of future scenarios are possible, and the imagination of entrepreneurs will play a key role.
Inevitably, private interests will move to develop orbital infrastructure and resources in response to a growing demand for space research and development. The permanent expansion of private commerce into low Earth orbit will be aided as the partners of the ISS commercialize infrastructure and support operations such as power supply and data handling. This trend is already under way with several commercial payloads having flown on the space shuttle and on the ISS.
The ISS is an unparalleled, international collaborative venture. In view of the global nature of the ISS, the international partners (sixteen countries) recognize the value of consulting on and coordinating approaches to commercial development. Each international partner retains the autonomy to operate its own commercial program aboard the ISS within the framework of existing international agreements, and mechanisms of cooperation are possible where desired.
see also Aging Studies (volume 1); Crystal Growth (volume 3); History of Humans in Space (volume 3); International Space Station (volume 3); Made with Space Technology (volume 1); Microgravity (volume 2); Mir (volume 3); Skylab (volume 3).
"The International Space Station: Improving Life on Earth and in Space; The NASAResearch Plan: An Overview." Washington, DC: National Aeronautics and Space Administration, 1998.
Messerschmid, Ernst, and Reinhold Bertrand. Space Stations: Systems and Utilization. Berlin: Springer, 1999.
Canadian Space Agency. International Space Station Commercial Utilisation. <http://www.space.gc.ca/business/com/iss/>.
European Space Agency. International Space Station Commercial Utilisation. <http://www.esa.int/spaceflight/isscommercialisation/>.
National Aeronautics and Space Administration. International Space Station. <http://spaceflight.nasa.gov/station/index.html>.
——. International Space Station Commercial Development. <http://commercial.hq.nasa.gov/>.
——. NASA Space Research. <http://spaceresearch.nasa.gov/>.
——. Space Product Development and Commercial Space Centers. <http://spd.nasa.gov/>.
*The ISS has a wingspan that is over a football field long.
International Space Station
International Space Station
The International Space Station (ISS), formally designated International Space Station Alpha, is a habitable orbital facility that has been under construction since 1998 and is scheduled for completion in 2006. When finished, it will contain about four times as much working space as the Russian space station Mir (1986–2001), the former record holder, and will weigh about one million pounds (453,000 kg). The ISS orbits at an average altitude of 240 mi (387 km). A number of science experiments are to be conducted aboard the ISS in such fields as health effects of radiation , molecular and cell biology , earth science , fluid dynamics , astronomy , combustion physics , and crystal growth.
History and structure
The ISS was originally proposed by U.S. President Ronald Reagan in 1984, and was slated to cost $8 billion. Thirty-six U.S. shuttle flights plus nine Russian rocket launches will be required for ISS construction. Today there are 15 major partners in the ISS effort, including the United States, Russia, Japan, Canada, and 11 of the member states of the European Space Agency. The United States, through its National Aeronautics and Space Administration (NASA), is the largest single contributor, bearing approximately $25 billion of the total $50–100 billion cost of building, launching, and operating ISS for at least a decade.
Assembly of the ISS commenced in 1998 with launch of the Russian control module Zarya on a proton rocket from Kazahkstan. The U.S. module Unity Node, a connecting segment, was carried into space on the shuttle Endeavor later in 1998. This unit is primarily a docking hub to which other sections join. In 2000, another Proton rocket lofted the Russian service module Zvezda, the main Russian contribution to the ISS. Zvezda provided living quarters and life support during the early phases of the ISS's growth; it also provides steering rockets to control the ISS's attitude (orientation in space) and to reboost it to higher altitudes as its orbit decays due to friction with high-altitude traces of the earth's atmosphere.
The ISS is powered by photovoltaic electricity . The first of its four large solar arrays (112 by 39 ft [34.2 by 11.9 m]) was added in 2000. When completed, the ISS will receive about 260 kilowatts of power (peak) from an acre of sun-tracking solar panels. An energy-storage sub-system consisting of six large nickel-hydrogen (Ni-H2) batteries supplies electrical power to the ISS during its passage through the earth's shadow, which lasts about 45 out of every 90 minutes.
In 2001, the U.S. laboratory module Destiny, the largest and most elaborate of the ISS's components, was added using the robot arm of the space shuttle Atlantis. The U.S. lab module contains 13 equipment racks, on which various scientific experiments will be mounted, and a 20-in (0.5-m) window set in the Earthside wall.
Smaller components were added piecemeal in 2002 by several shuttle flights, and in 2001–2002 several Russian flights ferried passengers and supplies. The ISS's final configuration will contain a European laboratory module, a Japanese laboratory module, three Russian laboratory modules, a Canadian robot arm to assist in assembly and maintenance, exterior racks for experiments requiring direct exposure to space, and an emergency Crew Return Vehicle on standby. The shuttle has been continuously inhabited since November 2, 2000, and presently houses a full crew of seven.
The ISS is intended to serve as a platform for the performance of scientific experiments that can only be carried out in space. The presence of a crew allows more complex experiments to be performed with simpler equipment than would be possible using purely robotic space vehicles; on the other hand, human beings require much complex gear to survive in space. Further, the ISS is not a particularly efficient platform for astronomical experiments, as it is vulnerable to by vibrations, and experiments that merely require a vacuum can be performed economically in vacuum chambers on Earth . Yet, the ISS does offer something that cannot be obtained for more than a few seconds at a time on Earth: weightlessness, or, more precisely (since the components of the ISS itself create a slight gravitational field), microgravity.
Unlike traditional science-fiction space stations, the ISS does not rotate in order to provide a centrifugal equivalent of gravity to its inhabitants. Such an arrangement would require a much more expensive structure due to the stresses imposed by rotation ; observational science experiments that need to point steadily at one part of the sky would be difficult to operate on a rapidly rotating platform; and rotation would destroy the very microgravitational conditions that make the ISS a unique place to conduct science.
Several of the experiments that have exploited (or will exploit) microgravity are the following:
Dendrite formation in solidifying metals. When metals solidify they tend, like snowflakes, to form branching or tree-like crystalline structures termed dendrites (from the Greek "dendrites," meaning "pertaining to a tree"). Observing the growth of metallic dendrites undeformed by the earth's gravity should help improve mathematical models of dendrite formation, which in turn may help in the design of stronger and more durable alloys.
Bone deterioration. As previous experience with long-term habitation of space has shown, persons living in weightlessness lose about 1% of their bone mass per month, even when performing bone-stressing exercises. Generations of small animals raised in space will enable biologists to study the effect of microgravity on genetic mechanisms of bone growth and resorbption. Understanding these mechanisms may someday make long space voyages (e.g., to Mars ) medically feasible.
Atomic clock. A French experiment will use microgravity to improve the accuracy of an atomic clock by a factor of 10 by observing oscillations of cesium atoms in free fall.
Commercial research. Between 30–40% of the U.S. lab module resources are reserved for use by private corporations, who will pay for access to microgravity research conditions. A slightly lower percentage of lab resources are reserved for commercial buyers in the European laboratory module. However, few corporations have yet purchased lab time on the ISS.
The ISS is enthusiastically supported by many people who are interested in space travel for its own sake and by those scientists who hope to fly their own experiments on the platform. However, it has long been heavily criticized by a majority of the scientific community for delivering too little science for the dollar and thus, in effect, diverting money from more effective research. Some scientists argue that the bulk of the research planned for the ISS addresses technical questions that are peripheral, rather than fundamental. For example, Science, the journal of the American Association for the Advancement of Science, complained in 1998 that the ISS's "greatest impact will be felt in the small community already studying problems related to spaceflight—a vital research area only if we assume that increasing numbers of people will someday travel, or even live, outside of normal Earth gravity." In other words, the ISS is an ultimately romantic project that puts astronauts in space in order to figure out how to put more astronauts in space.
The claim that the ISS has little to offer science was boosted by Russia's conveyance to the ISS of two private space tourists—officially designated Space Flight Participants—in 2001 and 2002, over loud protests from other ISS participant nations. Two wealthy men, one American and the other South African, paid $20 million apiece to the cash-strapped Russian government in exchange for a trip to the ISS.
Even before the loss of the space shuttle Columbia in February 2003, funding for completion of the ISS was in doubt. Both the United States Congress and the governments of the European Union have long been skeptical of the ISS's costs, and NASA was under such political pressure that it admitted it could not guarantee that the station will ever be grown beyond the "core complete" stage, with long-term living quarters for only three astronauts. Three astronauts, however, are not enough to tend the scores of experiments for which the ISS's racks have room, so if the ISS is not expanded much of the science potential already constructed will go to waste. Critics of the ISS argued that continued support for the ISS amounted to throwing good money after bad; supporters of the ISS counter-argued that ISS research is essential for make an eventual trip to Mars and that human space-travel projects generate valuable technological spinoffs.
The Columbia disaster of early 2003 has, as of this writing, made the ISS's future murkier. Although Russian rockets can supply many of the ISS's needs and ferry astronauts back and forth to it, only the space shuttle's cargo hold is large enough to carry many of the components planned for the ISS. Another, more urgent factor is that the ISS loses orbital altitude steadily due to friction with the outer fringes of the earth's atmosphere. Small rockets attached to the station regularly restore its altitude. The fuel for these rockets has been delivered via space shuttle, but after the Columbia disaster, a long delay seemed certain before frequent shuttle flights could be resumed, and Russian spacecraft have not been designed to deliver sufficient fuel. Engineers in both Russia and the United States have proposed alternate solutions, but as of March 2003 no firm course of action had been approved.
See also Gravity and gravitation; Spacecraft, manned.
Lawler, Andrew. "Can Space Station Science Be Fixed?" Science 5572 (May 24, 2002): 1387–1389.
Lawler, Andrew. "Space Station Research: Bigger Is Better for Science, Says Report." Science 5580 (July 19, 2002, 2002): 316–317.
Revkin, Andrew. "And Now, the Space Station: Grieving, Imperiled." New York Times, February 4, 2003.
"Tension and Relaxation in Space-Station Science." Nature 391 (February 19, 1998): 721.
Young, Laurence "The International Space Station at Risk." Science 5567 (April 19, 2002): 429.
International Space Station (ISS)
International Space Station (ISS)
The International Space Station (ISS) is the most complex international aerospace project in history. Sixteen countries contribute to this massive structure that measures 360 ft (110m) wide and 289 ft (88 m) long. At Earth's surface gravity , the ISS would weigh 503 tons (456,620 kg). Constructed from specialized component modules, the ISS is designed to allow humans to live in space for long durations of time and provide a laboratory for both scientific and engineering experiments. The modular design allows sections to be completed and tested on Earth before being booted into orbit. In addition, the modular design provides a level of security to ISS personnel. Damage from a failure or rupture of a component module can be isolated and the crew evacuated to safe modules. Modular designs are also economical because they allow rapid adaptation to the station to specific uses without having to subject the station to extensive retrofitting. In a engineering sense, the modular design allows maximum safety, design flexibility, and use adaptation at the lowest cost.
Long-range plans include use of the ISS as a spaceport where spacecraft can dock to transfer people, cargo, and fuel without having to re-enter Earth's atmosphere. Use of the ISS as a spaceport would thus, facilitate the construction of a fleet of true space vehicles—craft designed to operate exclusively outside Earth's atmosphere. Such craft would not need to be constructed to withstand the dynamic pressures of reentry, nor would their engine systems need to be designed to provide thrust capable of propelling the craft to high escape velocities.
Although the United States and Russia shoulder the bulk of the technological burden of ISS design and orbital placement, other nations, including Canada, Japan, the 11 nations of the European Space Agency (ESA) and Brazil significantly contribute to ISS development.
The United States is responsible for constructing and operating major ISS elements and systems. The U.S. systems include thermal control, life support, guidance, navigation and control, data handling, power systems, communications and tracking, ground operations facilities, and launch-site processing facilities. Canada is providing a 55-foot-long (16.8 m) robotic arm to be used for the station's assembly and maintenance. The European Space Agency is contributing a pressurized laboratory to be launched on the Space Shuttle , and logistics transport vehicles to be launched on an ESA Ariane 5 launch vehicle. Japan is providing a laboratory to be used for experiments and logistics transport vehicles. Russia is contributing two research modules, the Service Module, which includes early living quarters with life support and habitation systems, a science power platform that can supply 20 kilo-watts of electrical power, logistics transport vehicles, and Soyuz spacecraft for crew drop off and pick up. Through agreement with the United States, Italy, and Brazil are also providing ISS components and laboratory research facilities.
Approved by President Ronald Reagan in 1984, ISS (then designated Space Station Freedom ) development was put on hold by the turmoil and collapse of the Soviet Union in the late 1980s and the subsequent emergence of a revitalized Russian Space Agency in 1993. Broadened in scope to include a true international collaboration, in November of 1998, Russia launched the first part of the developing space station. More than four times as large as the Russian Mir space station, ISS assembly will continue until at least 2004.
ISS orbits at an altitude of 250 statute miles with an inclination of 51.6 degrees. This orbit allows maximum accessibility to the station for docking, crew rotation , and supply delivery. The orbit also allows for excellent observation of Earth. Orbital dynamics allow observation of up to 85% of Earth's surface and overflight of approximately 95% of Earth's heavily populated areas. Accordingly, the ISS is an ideal platform for the study of dynamic Earth geophysical processes and the long term study of the effects human civilization has upon both the physical and ecological landscape.
In addition to astronomical and Earth science research groups, the ISS will support medical and industrial research (e.g., the formation of certain alloys and crystals in low gravity environments).
See also History of manned space exploration; Space and planetary geology; Space physiology; Space probe; Spacecraft, manned
International Space Station
INTERNATIONAL SPACE STATION
The United States in 1984 initiated a program to build a space station—a place to live and work in space—and invited its allies in Europe, Japan, and Canada to participate in the project, which came to be called "Freedom." In 1993 the new presidential administration of Bill Clinton seriously considered canceling the station program, which had fallen behind schedule and was over budget. Space officials in Russia suggested as an alternative that the United States merge its space station program with the planned Russian Mir-2 program.
The United States accepted this suggestion and made it a key element of the redesign of what came to be called the International Space Station (ISS). The existing partners in the Freedom program issued a formal invitation to Russia to join the station partnership, which Russia accepted in December 1993.
There were both political and technical reasons for welcoming Russia into the station program. The Clinton administration saw station cooperation as a way of providing continuing employment for Russian space engineers who otherwise might have been willing to work on improving the military capabilities of countries hostile to the United States. Cooperation provided a means to transfer funds into the struggling Soviet economy. It was also intended as a signal of support by the White House for the administration of President Boris Yeltsin.
In addition, Russia brought extensive experience in long-duration space flight to the ISS program and agreed to contribute key hardware elements to the redesigned space station. The U.S. hope was that the Russian hardware contributions would accelerate the schedule for the ISS, while also lowering total program costs.
Planned Russian contributions to the ISS program include a U.S. funded propulsion and storage module, known as the Functional Cargo Block, built by the Russian firm Energia under contract to the U.S. company Boeing. Russia agreed to pay for a core control and habitation unit, known as the service module; Soyuz crew transfer capsules to serve as emergency escape vehicles docked to the ISS; unmanned Progress vehicles to carry supplies to the ISS; two Russian research laboratories; and a power platform to supply power to these laboratories.
The Functional Cargo Block (called Zarya ) was launched in November 1998, and Russia continued to provide a number of Soyuz and Progress vehicles to the ISS program. However, Russia's economic problems delayed work on the service module (called Zvezda ), and it was not launched until July 2000, two years behind schedule. As of January 2002, it was unclear whether Russia would actually be able to fund the construction of its two promised science laboratories and the associated power platform.
With the launch of Zvezda, the ISS was ready for permanent occupancy, and a three-person crew with a U.S. astronaut as commander and two Russian cosmonauts began a 4.5 month stay aboard in November 2000. Subsequent three-person crews are rotating between a Russian and a U.S. commander, with the other two crew members being from the other country. The crew size aboard ISS is planned to grow to six or seven after the European and Japanese laboratory contributions are attached to ISS sometime after 2005.
The sixteen-nation partnership in the ISS is the largest ever experiment in technological cooperation and provided a way for Russia to maintain its involvement in human space flight, which dates back to 1961, the year of the first person in space, Russian cosmonaut Yuri Gagarin.
See also: mir space station, space program
National Aeronautics and Space Administration. (2002). "International Space Station." http://spaceflight.nasa.gov/station.
Progressive Management. (2001). "2001—The International Space Station Odyssey Begins: The Complete Guide to the ISS with NASA and Russian Space Agency Documents." CD-ROM. Mount Laurel, New Jersey: Progressive Management.
John M. Logsdon