International Space Station: Continuing the Journey
[Reprinted from: http://mgnews.msfc.nasa.gov/spring98/lead.html
Spring 1998. This year marks the launch of the first segment of what is to be the International Space Station (ISS), and the excitement about this event, which is a triumph of both space engineering and international relations, is growing. The ISS will be a permanent orbiting laboratory that will allow researchers to conduct long-term experiments under microgravity conditions. The history of the long-awaited station is a considerable one. Such an immense undertaking could not take place without building on the talents, skills, and dreams of innumerable people fascinated by space and space travel -- from those who work with the program today to those who lived in the distant past.
From Fiction to RealitySpace stations have long been the stuff of imagination. The idea of humans living and working in space has enthralled scientists and visionaries for over a century. As far back as 1869, an American fiction writer named Edward Everett Hale published a story titled "The Brick Moon" in which he envisioned a manned satellite that served as a navigational aid for ships at sea (a function filled by unmanned satellites today). In 1903, Russian schoolteacher Konstantin Tsiolkovsky illustrated another type of space station vision when he depicted orbiting settlements that led to expeditions to the Moon, Mars, and asteroids in a book called Beyond the Planet Earth. This concept of establishing a space station as an "outpost in the wilderness," or a jumping-off point for further space exploration, became a very popular one that would show up again and again in writings about space.
Inspired by such fictional creations, scientists and engineers began to consider issues related to space outposts. In 1923, German physicist Hermann Oberth wrote The Rocket Into Planetary Space, in which he coined the term "space station." This influential work identified a wide range of problems related to rocketry and space travel and proposed solutions to them. Five years later, under the pseudonym Hermann Noordung, a German engineer named Herman Potocnik published a work that took the space station concepts even closer to reality. In The Problem of Space Travel, Potocnik laid out detailed engineering plans -- blueprints -- for an orbiting space station he called the "Habitat Wheel." These plans included over 100 illustrations of his station design, which consisted of modules constructed on Earth and carried to space via spaceships -- just as the modern ISS will be constructed. The modules were connected to each other in the shape of a wheel, and the entire station constantly rotated to simulate gravity by generating centrifugal force.
Potocnik was extraordinarily thorough in his plans, addressing such problems as obtaining power, heat, and light (he devised plans for a solar power plant attached to the station); providing ventilation to the station's inhabitants; and fabricating space suits that would allow humans to work on the exterior of the station safely. Potocnik's complete technical blueprint was the first to fully develop the notion of a space station, and many of his ideas, in modified forms, can be seen in modern technologies that will be used on the ISS.
In the 1950s, the space station concept found a powerful and creative supporter in rocketry pioneer Wernher von Braun. Having emigrated from Germany to the United States to build rockets for the U.S. Army in 1945, von Braun contributed a great deal to the early days of the U.S. space program, including his own version of a space station. Von Braun built on Potocnik's ideas, devising a space station that would take the shape of a rotating wheel, similar to the Habitat Wheel. Like Potocnik, he felt that inducing artificial gravity could prevent astronauts from suffering ill effects that could possibly be associated with long-term weightlessness. Von Braun's wheel, however, would be built of reinforced nylon and inflated in space prior to human occupation. According to his plans, the station would orbit 1,075 miles above the Earth and would serve as a navigational aid, a meteorological station, a military platform, and a way station for expanded space exploration, echoing and combining purposes proposed for such a station by those who had preceded him in imagining such a facility.
Put on Hold - A "Station Break"Plans for the development of a space station have been a part of NASA's agenda since the agency's inception. Like von Braun, many of NASA's trailblazers saw a station as a necessary prerequisite to further human exploration of space. Their reasoning was that a craft that had escaped Earth's gravity was already halfway to anywhere they wanted it to go. With an orbiting space station in place, missions to the Moon and Mars could be planned without having to deal with the difficulties of designing a vehicle that could both withstand the stress of escaping the Earth's atmosphere and address the issues inherent in long-term microgravity spaceflight. Instead, astronauts would fly one type of craft to the space station, and then transfer to another sort of craft for extended travel, similar to the space travel depicted in the movie 2001: A Space Odyssey.
When the United States embarked on a "space race" with the Soviet Union in the 1960s, however, the notion of a space station as a prerequisite to space travel was deferred. President John F. Kennedy's promise to put a man on the Moon before the end of the decade resulted in the decision to pursue a different model -- the lunar orbit rendezvous model -- for getting to the Moon, and plans for building a space station were put on the back burner. As a result, although the United States was the first nation to send a human being to the Moon, the Soviet Union ended up being the first nation to have an inhabited space station in orbit.
Skylab's Day(s) in the SunIn the meantime, NASA was working on its own space station program. Despite a somewhat unsupportive political environment under the administration of President Richard Nixon, NASA embarked on a plan that would use some of the technologies developed under the Apollo program to launch an unoccupied station called Skylab to orbit. Skylab was designed to be a precursor to a long-term space station, and one of its purposes was to prove that humans could live and work in space for extended periods of time. The station, launched on May 14, 1973, got off to a rocky start; during launch, its meteorite shield/sunshade was torn loose and one of the solar arrays (mechanisms by which the station collected power from the Sun) was destroyed. The subsequent launch of Skylab's first crew, which was supposed to have been immediate, was delayed for 10 days while NASA teams worked to figure out how to fix the crippled station.
A solution was found, and the Skylab-2 crew (the Skylab-1 designation was used for the launch of the station itself) was sent to rendezvous with the station. The first task of their 28-day stay aboard the station was to create a "parasol" out of foil to replace the damaged sunshade. The makeshift shade worked, lowering the temperature inside the station from a sweltering 126 degrees Fahrenheit to 75 degrees. The crew also performed spacewalks to repair the damaged solar array, supplying the station with power. For the rest of their stay, the astronauts conducted experiments aboard the station, with an emphasis on medical experiments designed to assess the effects of long-duration microgravity on the human body.
Over the course of its lifetime, Skylab played host to two more crews of three astronauts each. The Skylab-3 crew lived onboard the station for 59 days, doubling the previous endurance record in space. Skylab-4 crewmembers set another impressive record with a stay of 84 days (November 16, 1973-February 8, 1974) -- an American record that stood until astronaut Norm Thagard broke it with a 115-day stay aboard the Russian space station, Mir, in 1995. After the last crew left Skylab, the station remained in space until its orbit deteriorated, causing it to fall harmlessly to Earth in 1979.
Advances in Soviet StationsThe Soviets continued to refine the Salyut program in the late 1970s, and a second generation of Salyut space stations was begun in 1977. With the launch of Salyut 6, the Soviet program progressed from short-duration stays in space to long-duration stays -- the first crew beat the American space endurance record, set on Skylab in 1974, with a stay of 96 days. The new type of station had two docking ports, one on each end of the cylindrical module, which meant that crews could remain at the station for a long period of time, with fuel and new supplies arriving at the second docking port via Progress ships. The second port also allowed Salyut crews to receive visitors aboard the station; cosmonaut researchers would arrive at the station to conduct research for a short period of time and then return to Earth, often trading in their Soyuz capsule for the one already docked at the station (the Soyuz ships had a limited lifetime in orbit). Salyut 6 played host to six long-duration cosmonaut crews, with the longest time in orbit being 185 days. In 1982, Salyut 7 (almost identical to Salyut 6) was placed in orbit; from 1982 to 1986, the station hosted six more long-duration crews, one of which was in orbit for 237 days. Salyut 7 was abandoned in 1986, and it re-entered Earth's atmosphere in 1991.
Fulfilling Another Presidential MandateIn 1984, the United States began with its plans for what has ultimately become the International Space Station. As part of his State of the Union address that year, President Ronald Reagan directed NASA to develop plans for a permanently manned space station "within a decade." Stated Reagan, "A space station will permit quantum leaps in our research in science, communications, in metals, and in lifesaving medicines which could be manufactured only in space." The mandate was reminiscent of Kennedy's call for putting a man on the Moon, and NASA immediately began to put their plans in motion. At that time, the space shuttle program had been in place for over three years, and the rewards of conducting experimental research in the microgravity environment of orbit were becoming more and more clear. No longer was a space station seen only as a jumping-off point for further human exploration of space; instead, a primary benefit of a space station was identified as the ability to provide a permanent laboratory in which researchers could conduct long-term microgravity experiments.
In his address, Reagan also called for the station, which was subsequently named Space Station Freedom, to be an international effort: "We want our friends to help us meet these challenges and share in their benefits. NASA will invite other countries to participate so we can strengthen peace, build prosperity, and expand freedom for all who share our goals." By forging relationships with nations that had already established space programs, the space station program would be strengthened and given more legitimacy. Thirteen countries (Japan, Canada, and those countries that made up the European Space Agency [ESA]) originally signed agreements in the spring of 1985 to partner in the endeavor, which would be of epic proportions. The station was to consist of multiple modules, and each partner took on responsibility for different components of the station.
Freedom's design was complex and ambitious. Attempting to scale back the project, NASA redesigned the station several times, trying to reduce costs, stick to a reasonable schedule, and still satisfy the demands placed on the station by its diverse supporters. This task proved next to impossible, and many of the station's previous supporters felt that the compromises being made regarding the station had adversely affected its potential. Things came to a head in 1993, when President Bill Clinton, newly in office, issued a directive to NASA instructing the agency to restructure the space station program to reduce costs and maximize scientific use. NASA went back to the drawing board. The outcome of NASA's re-evaluation of the program was the development of three alternative designs for the space station of varying cost and usefulness in the summer of 1993. The decision was made to proceed with the "Alpha" design, which incorporated many of the features of Space Station Freedom and which was moderately priced and useful to scientists and researchers. The Space Station Alpha design has evolved into what is now called the International Space Station. Around the same time, NASA negotiatedwith Russia in an effort to bring them into the international association of space station partners. The inclusion of Russia in space station planning was seen as beneficial both to Russia and to the international coalition, especially since Russia had a great deal of experience in assembling and maintaining a long-duration modular space station in Earth orbit.
Space Station Mir had been launched and maintained by the Soviet Union, and subsequently by Russia, since 1986. The design of Mir had advanced beyond the days of Salyut; the station was constructed of several modules that were each launched separately and then assembled while in orbit. This multimodular construction was similar to what was planned for Space Station Alpha.
At the time of the U.S.-Russian agreement involving Russia in the construction of the ISS, Mir had been in orbit for seven years and had been continuously occupied for four years. The Soviets (and subsequently, the Russians) had made great strides in the areas of engineering docking mechanisms and developing resupply and refueling techniques, and their expertise was seen as a benefit to the ISS program. After Russia became an ISS partner, NASA embarked on several jointly funded research projects with Russia aboard Mir in preparation for conducting research on the ISS. In addition to these projects, some of which are still under way, seven U.S. astronauts have spent a total of more than 22 months living and working aboard Mir to date, including Shannon Lucid, who holds the American record for the longest time in space -- 188 days. Of course, this record comes nowhere near Russian cosmonaut Valeri Poyakov's record of more than 438 days in space. The NASA-Mir program has been referred to as Phase I of the ISS program, and the lessons learned from the program are numerous.
Realizing Our Common DreamNASA and its partners currently stand on the brink of finally making the dream of an international station a concrete reality. The coalition of international partners has expanded to number 16 countries in all: Belgium, Brazil, Canada, Denmark, France, Germany, Italy, Japan, the Netherlands, Norway, Russia, Spain, Sweden, Switzerland, the United Kingdom, and the United States. In January 1998, all of the space station partners, except Brazil, signed new intergovernmental agreements establishing the framework for the assembly of the ISS over the next five years. The launch of the first module this year will begin the assembly process of piecing together more than 100 space station components. When completed, the ISS will be a platform for research and international cooperation well into the next century. The journey from the imaginations of science fiction writers to the physical reality of an international space station has been a long one -- but in many ways, the journey is just beginning.
Created: Sunday, October
07, 2007; Last Updated:
Saturday, March 14, 2015