On each mission, when not subjecting themselves to medical and psychological testing, space station crews perform hundreds of scientific experiments. All experiments are selected by a panel of NASA scientists from thousands of suggestions. Each is then carefully planned and all needed hardware is assembled. Prior to liftoff, each crew rehearses the steps required for each experiment to minimize failures. Much is at stake: Multimillion-dollar projects can be rendered useless if an experiment is botched.
Scientists representing nearly all major branches of knowledge have jockeyed to gain permission to conduct experiments on Salyut, Skylab, Mir, and the ISS. Everyone has recognized that their unique environments, far beyond Earth's atmosphere and floating in weightlessness, hold extraordinary potential for new discoveries in many fields. Those fields given the highest priority have been astronomy, earth environmental study, material development, botany, combustion and fluid physics, and military reconnaissance.
The point of research in space, in the view of most scientists, is principally to improve human life on Earth. From this research they believe will come knowledge and discoveries that will change and improve everyone's lives on Earth, from the foods that people eat, the cars they drive, the computers they use, and even medical procedures used by physicians.
First with Salyut and Skylab, then with Mir, and today with the ISS, one of the key focuses of scientific exploration has been furthering human understanding of the cosmos. All space stations have carried instrumentation of various types on their missions miles above Earth to provide astronomers with clearer images of planets, stars, and galaxies than even the largest telescopes on Earth can offer.
The principal reason astronomers are interested in mounting their instruments on space stations is that they operate far above Earth's atmosphere, which obscures astronomers' views due to dust particles, changing temperatures, and moisture in the form of clouds, rain, and fog. In addition, light from large
One of the earliest attempts at placing a telescope on a space station occurred on Salyut for the purpose of investigating the Sun. Skylab followed with the Apollo telescope mount (ATM), a canister attached to the space station and containing a conventional telescope with lenses that could zoom in on a solar event such as sunspots. It also carried ultraviolet cameras that, thanks to sophisticated mounts, could be aimed steadily and precisely at any point on the Sun regardless of disturbances, such as those caused by crew movement. The instruments provided astronomers with thousands of remarkably detailed photographs of the Sun's surface and of solar flares.
With the launch of Mir, which carried state-of-the-art instrumentation, photographs deeper into space became possible. Soviet cosmonauts conducted a photographic survey of galaxies and star groups using the Glazar telescope. Because the telescope was pointed hundreds of millions of miles into deep space, far beyond the solar system, the amount of light being captured was so small that exposure times up to eight minutes were required to capture enough light for a single photograph. Under such circumstances, even the slightest vibrations from astronaut movements could shake the space station and ruin the photograph. As a result, all astronauts were required to sit, strapped into chairs, during these long exposures.
Of greatest excitement to astronomers today is a new generation of telescope, already built, tested, and secured on the ISS. This telescope, called the Submillimetron, is unique in three significant ways. First, as its name suggests, it detects and photographs very short wavelengths of light, much shorter than sunlight. These short microlight waves were emitted billions of years ago, when the universe was first formed. Astronomers believe that these images, then, are of cosmic bodies formed close to the beginning of the universe. Second, such a unique and precise instrument is designed to operate at supercold temperatures using liquid helium to chill sky-scanning equipment, thereby increasing the sensitivity of the Submillimetron's telescopic gear by slowing the motion of the molecules. A third unique feature allows for normal crew activity at all times, despite the extreme sensitivity of the equipment and extreme distances it photographs. The Submillimetron undocks from the ISS before it is used and then redocks for necessary maintenance. Astrophysicists interested in both the origin and ultimate fate of the universe are particularly interested in the Submillimetron's capabilities.
Environmentalists and biologists recognize the value of space stations as a unique means to gain the broadest possible view of Earth as well as detailed views of particular environmental hot spots. When Earth is viewed from space through a variety of infrared and high-resolution cameras, natural resources can be identified, crops can be surveyed, and changes in the atmosphere and climate can be measured. Events on the surface, such as floods, oil spills, landslides, earthquakes, droughts, storms, forest fires, volcanic eruptions, and avalanches can be accurately located, measured, and monitored.
One of the earliest and most successful environmental projects carried out aboard a space station was the use of a scatterometer on Skylab. A scatterometer is a remote-sensing instrument capable of measuring wind speed and direction on Earth under all weather conditions. When it was activated on Skylab, the scatterometer captured wind speed and direction data once a second and transmitted the data back to Earth. Engineers analyzed the data and used it to forecast weather, warn ships at sea of approaching heavy storms, assisted in oil spill cleanup efforts by accurately predicting the direction and speed the oil slick was taking, and notified manufacturers of hazardous chemicals of the safest times to ship their products.
Mir also proved its value to environmental science. One of Mir's modules, called "Priroda," a Russian word meaning "nature," was launched in April 1996. Priroda carried equipment to study the atmosphere and oceans, with an emphasis on pollution and other forms of human impact on Earth. It also was capable of conducting surveys to locate mineral resources and underground water reserves as well as studies of the effects of erosion on crops and forests.
To accomplish these ambitious objectives, environmental engineers loaded Priroda with active, passive, and infrared sensors for detecting and measuring natural resources. It carried several types of spectrometers used for measuring ozone and fluorocarbon (the chemical found in many aerosols) concentrations in the atmosphere. At the same time, equipment monitored the spread of industrial pollutants, mapped variations in water temperatures across oceans, and measured the height of ocean waves, vertical structure of clouds, and wind direction and speed.
When the ISS went into space in 1998, environmental studies were high on the list of projects for the astronauts to work on. From the ISS orbit, 85 percent of Earth's surface can be observed. Continuously monitoring and investigating Earth from space with an impressive array of high-tech instrumentation, the ISS has facilitated in the identification of many environmental problems. In 2001 the commander of the ISS, Frank Culbertson, shared with the British Broadcasting Corporation the many observations he and other astronauts had made after studying Earth's
Designers of the ISS wished to add a special portal on one of the modules through which astronauts could gaze at and photograph Earth and neighboring planets. Gazing out into space was not new, but previous windows were made of glass that easily scratched, clouded, and discolored. In an effort to correct these defects, optical engineers created the Nadir window, named after the astronomical term describing the lowest point in the heavens directly below an observer.
Mounted in the U.S. laboratory module element of the space station, the twenty-inch diameter Nadir window provides a view of more than 75 percent of Earth's surface, containing 95 percent of the world's population. Designed by Dr. Karen Scott of the Aerospace Corporation, the high-tech five-inch-thick window is actually a composite of four laminated panes consisting of a thin exterior "debris" pane that protects it from micrometeorites, primary and secondary internal pressure panes, and an interior "scratch" pane to absorb accidental interior impacts. Each has different optical characteristics.
Scott headed a team of thirty optical engineers that used a five-hundred-thousand-dollar optical instrument to make fine calibration measurements on the window to ensure precise clarity free of distortion before installing it in the lab module. Tests conducted on the multiple layers of the window ensured that they would not distort under the varying pressure and temperatures common on the space station. After five days of extreme testing, the unique window was determined to have the characteristics that would allow it to support a wide variety of research applications, including such things as coral reef monitoring, the development of new remote-sensing instruments, and monitoring of Earth's upper atmosphere.
environment for four months. High above Earth, Culbertson made some startling observations:
We see storms, we see droughts, we saw a dust storm a couple of days ago, in Turkey I think it was, and we have seen hurricanes. It is a cause for concern. Since my first flight in 1990 and this flight, I have seen changes in what comes out of some of the rivers, in land usage. We see areas of the world that are being burned to clear land, so we are losing lots of trees. There is smoke and dust in wider spread areas than we have seen before, particularly as areas like Africa dry up in certain regions. 26
Since 2000, NASA has been conducting cellular research on board the ISS to take advantage of the weightless environment to study cell growth and the intricate and mysterious subcellular functions within cells. Traditionally, biologists study cells by slicing living tissue into sections of single-cell thickness. The drawback to this process, for as long as it has been practiced, is that the prepared specimens begin to die within a few hours as the cells begin to lose their ability to function normally. At best, researchers on Earth have only one day to scrutinize under microscopes the workings of minute structures within cells. The problem that occurs when single cells are removed from a living organ for examination is that microscopic structures crucial to the life of the cell collapse, causing the cell to cease functioning.
This research has primarily focused on the functioning of cells in the human liver, the organ that regulates most chemical levels in the blood and breaks down the nutrients into forms that are easier for the rest of the body to use. In a weightless environment slices of liver one-cell thick remain healthy and active for up to seven days, a significant advantage for researchers in space over those working on Earth. According to Dr. Fisk Johnson, a specialist in liver disease under contract with NASA, "Space is the gold-standard environment for this cutting-edge cell research. Only in space, a true microgravity environment, will we be able to isolate and study each of the individual factors impacting cell function." 27
Once this advantage was discovered, the question then arose of how medical researchers on Earth could gain the same advantage. That question was answered by medical laboratories working with NASA that developed a device called a rotating bioreactor, which is capable of simulating a weightless environment on Earth. The rotating bioreactor works by gently spinning a fluid medium filled with cells. The spinning motion neutralizes most of gravity's effects, creating a near-weightless environment that allows single cells to function normally rather than collapse as they would otherwise do.
Utilizing the rotating bioreactor on Earth in the year 2002 scientists successfully accomplished long-term culturing of liver cells, which allows the cells to maintain normal functions for six days. One of the advantages of studying healthy cells for a long time is the ability to identify and match cellular characteristics to drugs that might cure particular diseases. According to Dr. Paul Silber, a liver specialist, "Our recent discoveries could lead to better, earlier drug-candidate screening, which would speed up drug development by pharmaceutical companies, and importantly, to a longer life for the 25,000 people every year waiting for a life-saving liver transplant." 28
The weightless environment on space stations was of as much interest to materials scientists as to any others. Scientists are interested in a variety of physical properties of materials, such as melting points, molding characteristics, and the combining or separating of raw materials into useful products. Before the first space stations, materials scientists performed simple experiments of very short duration aboard plummeting airplanes and from tall drop towers. Through these studies, scientists discovered that gravity plays a role in introducing defects in crystals, in the combination of materials, and in other processing activities requiring the application of heat. Until the advent of space stations, however, they were incapable of sustaining a weightless environment long enough to thoroughly study these phenomena.
The advent of space stations allowed the study of new alloys, protein crystals for drag research, and silicon crystals for use in electronics and semiconductors. Materials scientists theorized that improvements in processing in weightlessness could lead to the development of valuable drugs; high-strength, temperature-resistant ceramics and alloys; and faster computer chips.
One of the Mir components, the Kristall module, was partially dedicated to experiments in materials processing. One objective was to use a sophisticated electrical furnace in a weightless environment for producing perfect crystals of gallium arsenide and zinc oxide to create absolutely pure computer chips capable of faster speeds and fewer errors. Although they failed to create absolutely pure chips, they were purer than those they could create within Earth's gravitational field.
More recently, fiber-optic cables are also being improved in weightlessness. Fiber-optic cables, vital for high-speed data transmission, microsurgery, certain lasers, optical power transmission, and fiber-optic gyroscopes, are made of a complex blend of zirconium, barium, lanthanum, aluminum, and sodium. When this blend is performed in a weightless environment, materials scientists are finding them to be more than one hundred times more efficient than fibers created on Earth.
In 2002 the ISS began the most complex studies of impurities in materials and ways to eliminate them in a microgravity environment. One of the more interesting causes of impurities, for example, is bubbles. On Earth, when metals are melted and blended, bubbles form. According to materials scientist Dr. Richard Grugel, "When bubbles are trapped in solid samples, they show up as internal cracks that diminish a material's strength and usefulness." 29 In a weightless situation, however, although bubbles still form, they move very slightly, and this reduces internal cracks. Secondarily, their slow movement allows researchers to study the effect of bubbles on alloys more easily and precisely.
According to Dr. Donald Gillies, NASA's leader for materials science, the studies of bubbles and other mysteries of materials production hold promise for new materials:
We can thank advances in materials science for everything from cell phones to airplanes to computers to the next space ship in the making. To improve materials needed in our high-tech economy and help industry create the hot new products of the future, NASA scientists are using low gravity to examine and understand the role processing plays in creating materials. 30
For centuries, physicists and chemists have been experimenting on a variety of elements and metals to discover new compounds and to improve existing alloys. They have also been aware that their experimental results are often affected by the containers they use and by the instruments that measure those results. Such contamination often invalidates experiments. Even worse, containers can sometimes dampen vibrations in a material or cool the sample too rapidly, throwing the validity of the experiment into doubt. In some cases, a metal is reactive enough to destroy its container, meaning that some materials simply cannot be studied on Earth.
When the first space stations went into orbit, physicists and chemists seized on the opportunity to conduct experiments within a weightless environment. If materials could be suspended in space during experiments, without the need for containers and eliminating the variables that the containers themselves imposed, far more accurate results would be allowable. Initial results of such experiments answered many questions that could not have been resolved on Earth. Of particular interest was the property of metals in a liquid state that causes them to resist solidifying, even at temperatures where they would be expected to do so. This phenomenon is called nucleation. According to Dr. Kenneth Kelton, a physics professor at Washington University in St. Louis, "Nucleation is the major way physical systems change from one phase to another. The better we understand it, the better we can tailor the properties of materials to meet specific needs." 31
Encouraged by the results of experiments carried out in space, engineers developed an apparatus on Earth that could duplicate a weightless environment for further research. NASA, joined by several private research companies, developed the electrostatic levitator (ESL), which is capable of suspending liquid metals without the sample touching the container and without the technicians handling equipment in ways that might alter results. Two practical applications using the ESL are the production of exceedingly smooth surfaces for computer and optical instrumentation and exceedingly pure metal for wires, making them capable of transmitting large volumes of data.
While materials scientists look to space station experiments in hopes of improving industrial processes on Earth, others are focused on investigating processes that might someday happen on a large scale in space. For example, botanists are studying the feasibility of crop cultivation on space stations in the belief that grains and vegetables may someday be needed in quantities large enough to supply deep space expeditions or even space colonies. To these ends, many experiments have been performed testing different gases, soils, nutrients, and seeds. One of them, called seed-to-seed cycling in a weightless environment, produced remarkably optimistic results. According to biologist Mary E. Musgrave:
By giving space biologists a look at developmental events beyond the seedling stage, this experiment was an important contribution not only to gravitational biology, but also to the study of space life support systems. Data from this experiment on gas exchange, dry matter production and seed production provided essential information on providing a plant-based food supply for humans on long-duration space flights. 32
Many of the botanical experiments in orbit have focused on the effects of weightlessness on plant growth and seed germination. Botanists had known for many years that seedlings on Earth display geotropism—that is, they respond to gravity by sending their roots down into the soil and stalks up above the ground. In addition, gravity affects the diffusion of gases given off by the plant, the drainage of water through soil, and the movement of water, nutrients, and other substances within the plant.
Early experiments aboard Skylab were not encouraging for those who hoped to grow plants in space. For example, researchers' speculations were confirmed that without gravity, the roots and stalks of plants could not correctly orient themselves. Some seedlings sent their roots above the soil and their stalks deep into the soil, with the result that they withered and died. And even those that did properly orient their roots and stalks often failed to produce seeds, a critical failure unanticipated by researchers.
In the mid-1980s, botanists performed an experiment to understand how seeds might survive weightlessness. Scientists sent 12.5 million tomato seeds into space and kept them there aboard Mir for four years. In 1990 the seeds were planted by botanists; many were also given to schoolchildren so they could make science projects of germinating them. Botanists discovered that a slightly higher percentage of seeds from space germinated than did seeds that had been kept on Earth and that almost all produced normal plants. These results were achieved even though the seeds had been exposed to radiation while in space.
A second significant experiment on the ISS sought to determine whether second-generation space plants would be as healthy as second-generation plants on Earth. Scientists analyzing the data concluded that the quality of second-generation seeds produced in orbit was lower than that of seeds produced on Earth, resulting in a smaller second-generation plant size. This diminished seed quality is believed to be caused by the different ripening mechanics inside the seed pod in weightlessness.
With so much evidence pointing to weightlessness as a hostile environment for plant production, botanists are a bit uncertain of the future of agriculture in space. One potential solution being investigated on the ISS is to grow plants without soil, a process known as hydroponics. In this process, the plants grow without soil, in a nutrient-rich solution.
In addition to their promise for scientists, space stations from the very beginning were seen as having military value. During the Cold War, when the United States and the Soviet Union jockeyed for political and military advantage on Earth, each country also looked to space stations to give them battlefield superiority. Although neither nation actually placed offensive weapons on board their space stations, both sought to exploit space stations' potential for reconnaissance.
All space stations have carried equipment capable of photographing objects 250 miles below. Photographs are detailed enough, for example, to allow analysts to determine the types and numbers of aircraft on aircraft carriers and to track troop movements on land.
Yet, military officials admit that so far, at least, space outposts can do little more than support more conventional military operations. At a meeting of the American Institute of Aeronautics held in Albuquerque, New Mexico, in August 2001, Colonel Steve Davis, an officer at Kirtland Air Force Base, said, "We're [the Air
When NASA and the Russian Space Agency negotiated the initial agreement for the construction, deployment, and utilization of the ISS, no one gave consideration to using it as a tourist destination. From the inception of the project, all countries involved considered the ISS to be an orbiting laboratory dedicated to the study of a variety of scientific experiments and observations.
This somewhat parochial view was shaken in 2001 when the multimillionaire American businessman Dennis Tito expressed an interest in paying for a short vacation on the ISS to satisfy his own personal fascination with space. When NASA was notified of his interest and willingness to pay for a short visit to the spacecraft, his request was rejected on the grounds that the multibillion-dollar craft was for scientific purposes only. Recognizing that the Russians were short of money needed to continue their construction and launch costs, Tito approached them with an offer of $20 million.
Brushing aside NASA's objections, the Russians required Tito first to complete the standard training program before being blasted on what most called the most expensive vacation ever. In May 2001, when Tito docked at the ISS, several important milestones were achieved. These included the fact that a middle-aged civilian astronaut could easily survive space travel, that a space-tourism market did indeed exist, and that there was no longer a valid reason to discount the notion of space tourism.
Despite NASA's long-running opposition to his flight, which included preventing him from training with his Russian crewmates at the Johnson Space Center that triggered a minor international incident, Tito said he enjoyed his eight days in space and hoped that NASA would be more supportive in the future.
Force] still looking for that definitive mission in space; force enhancement is primarily what we're doing today." Davis added that there is increasing reliance on using space for military needs: "Space control is becoming more important as we have very high value assets in orbit. We depend on these assets and are interested in protecting them." Davis added that aboard one of the Soviet Union's early orbital piloted stations, it had a rapid-fire cannon installed. The military outpost was armed, Davis said, "so they could defend themselves from any hostile intercepts." 33
Even the ISS is seen by some participating nations as having military value. An intergovernmental agreement on the ISS was first put in place in 1988, resulting in an exchange of letters between participating countries involved in the megaproject. Those letters state that each partner in the project determines what a "peaceful purpose" is for its own element. According to Marcia Smith, a space policy expert at the Congressional Research Service, a research arm of the U.S. Congress, "The 1988 U.S. letter clearly states that the United States has the right to use its elements . . . for national security purposes, as we define them." 34
One of the more perceptive observations made when the first space stations flew into orbit was the potential that these floating laboratories might provide for investigating and solving a multitude of scientific questions. To a great degree, those making these observations were correct. Nearly every branch of science jumped on the space station bandwagon with proposals to investigate a host of questions. As the twenty-first century pushes forward, many problems of living in space have been solved while others remain elusive. The question being asked more frequently than ever is whether the costs of the many space stations and their experiments have returned enough benefits to taxpayers to continue the space station program.