The Death of a Space Station

Relegating space stations to the junk heap is both a tricky and complicated proposition. All space stations will eventually fall out of orbit and plummet back to Earth—unless regularly propelled back into orbit—as their speed and altitude drop due to Earth's gravitational pull. In 1991 Russian aerospace engineers finally allowed Salyut 7 to fall out of orbit and plummet to Earth. Unfortunately, Russian space engineers had no idea where it would hit the earth, and even after disintegrating as it plunged through the atmosphere, several tons of debris eventually scattered across the Andes mountains, much to the anger of many people.

Hoping to avoid another international incident, the Russians planned better when the time came to bring Mir out of orbit. In March 2001 the world was notified that the 130-ton Mir would be brought down somewhere over the Pacific Ocean, the largest unpopulated region on Earth. As the space station gradually lost altitude, the date of splashdown in the Pacific was announced as March 21. Soviet engineers announced that as it passed through the atmosphere at initial speeds of seventeen thousand miles per hour, 110 tons of the 130-ton craft would burn up from friction; the surviving 20 tons would scatter into thousands of small pieces that would splash into the ocean.

Hitting the Pacific on a particular day would require control. Soviet engineers conceived the idea of actually accelerating Mir's descent through the atmosphere to control the time and place of disintegration. To accomplish this objective, a Progress cargo ship was attached to the station, which had a rocket propulsion system. When Mir fell to about 136 miles, the rocket engines on Progress would be fired to accelerate Mir downward into the thicker layers of the atmosphere, where it would quickly break apart and burn.

The controlled reentry was projected to bring the craft down in a 380,000-square-mile swath of the Pacific between New Zealand and Chile, away from major air and sea routes. Tiny nations throughout the South Pacific were alerted to watch for the chunks of Mir, and dozens of island authorities warned their people not to go out March 21 and to stay off boats to avoid being hit by any parts.

In a trip condemned as suicidal by Russia's space agency, a California-based public relations firm chartered an airplane for a group of space enthusiasts and television crews to fly to the site. They hoped to photograph the blazing reentry, but NASA authorities estimated their chances of being hit as about 1 in 2 billion. Fortunately for everyone, the plan worked and the blazing scraps of Mir plunged harmlessly into the Pacific.

called for the locking of the remaining modules by the end of 2003, with experiments beginning immediately and running continuously until at least 2013.

Everyone involved in the project understood that the ISS would be the culmination of thirty years of research and experimentation on Salyut, Skylab, and Mir. Far from being just the next iteration of space stations, aeronautical engineers worked to make the ISS a second quantum leap in the wake of its predecessor, Mir. According to Daniel Goldin, the head of NASA, the ISS would push space station technology far beyond Mir:

The International Space Station (ISS) will change the course of human history. The ISS is certainly an ambitious idea. It is probably the largest international scientific and technological project ever undertaken. The goal is to establish and maintain a permanent presence in space and to provide a testbed for new technologies, medical research, and the development of advanced industrial materials.10

The design of the ISS would be on a scale that would dwarf Mir. Rather than the total of five modules that Mir had, designers planned for six primary modules used exclusively as laboratories in addition to additional modules for crew quarters, storage facilities, docks for transport vehicles, and airlocks needed for space walks. All of these modules, when coupled with six pairs of solar panels and external apparatuses such as telescopes and communications antennae would give the ISS the look of an oversized spider moving through space.

An artist's conception of the completed International Space Station shows its huge, spidery form. Five international space agencies are collaborating on the project.

Significantly larger than Mir, the ISS structure would have an overall length of 262 feet, a width of 365 feet, and a total weight of a massive 500 tons, nearly four times the weight of Mir. NASA engineers liken the total exterior space to the dimensions of two football fields and the interior space to that of the passenger cabin of a Boeing 747. Equally remarkable will be the ability of the ISS to accommodate a crew of seven—more than twice the capacity of Mir.

International Cooperation

The first step toward building the ISS was assigning responsibilities and costs to each of the charter nations. In 1993 most of the details of the joint space contract were ironed out and agreed upon. In his book Living in Space: From Science Fiction to the International Space Station, space writer Giovanni Caprara comments on this agreement:

The signing of the joint space agreement marked the end of an era of antagonism [between Americans and Russians] and the beginning of a new phase of cooperation. . . . Until now, space programs had been viewed as an ideal means of demonstrating the superiority of a political system. Now they became a proving ground for experiments in cooperative agreements that could be usefully applied to other fields.11

The United States and Russia were joined in the construction effort by a consortium of ten European nations—called the European Space Agency (ESA)— as well as by Canada and Japan. Engineers realized that overcoming the forty years of competition between the United States and Russia would be an asset to the new space station. Canada declared its intention to construct the robotic arm that would be used for assembly of the ISS modules and for placement and retrieval of a variety of equipment for experi ments. Fifty-seven feet long, 15 inches in diameter, and weighing 911 pounds, the robotic arm derives its flexibility from six revolving joints and its grasping ability from pincers designed to maneuver a 266-ton object while in orbit. Since the robotic arm would be an essential component for assembly of the ISS, it would be one of the first items flown to the station.

Japan announced its interest in building a module called the Japanese Experiment Module (JEM), intended to be a multipurpose facility for a variety of space science and technology studies. Nicknamed "Kibo," the JEM is a cylinder thirty-seven feet long and ten feet in diameter. Attached to Kibo is an external platform similar to a back deck, called the Exposed Facility, available as a storage unit and laboratory for conducting experiments intended to be performed in a vacuum.

The ESA, which consisted of three major contributors— France, Germany, and Italy—and seven minor ones, agreed to contribute a research module called the Columbus Orbital Facility and a transfer vehicle that would be used to transport supplies to the ISS and to boost the orbit of the station to a higher altitude if needed.

Russia, the country with the most experience in long-term missions on space stations, was called upon to make a considerable contribution to the ISS. Russia agreed to build the first module that would go into orbit, the FGB, which is the Russian acronym for Functional Cargo Block. It would function as the control center for the ISS, providing docking ports, fuel tanks, and solar panels. Weighing nineteen tons, this forty-foot-by-twelve-foot cylinder would be the largest of the ISS modules. The Russians also agreed to supply at least two science modules, additional solar panels, resupply vehicles, and, of critical importance, an escape vehicle to be used in the event of some catastrophe on the ISS that would necessitate the crew's evacuation. Russia's one last major contribution, the Proton rocket, would muscle the main pieces into space, requiring an estimated ninety launches.

America's role began with building Node 1, named "Unity," which would function as conduit for power, liquids, gases, and communications needed by all the other modules. Next, the United States built the American Laboratory, which was intended to be used for a variety of experiments; the United States would also supply eight solar panels. America agreed to provide the space shuttle, which, along with the Proton rockets, would fly the ISS modules into orbit and provision them over the life of the space station.

Leading-Edge Technologies

ISS engineers applied the latest leading-edge technologies to create a safe interior work space for the crew. Each module has an outer shell of lightweight aluminum. This shell has an additional protective layer of four-inch-thick impact-resistant Kevlar and ceramic material. This layer functions as a bulletproof vest to provide extra protection from impacts by micrometeoroids and tiny grains of grit that punctured previous space stations, causing air leaks.

Another significant departure from Mir's design is the high degree of specialization of each ISS module. This specialization of function necessitates a great deal of interdependence with other modules. Unlike Mir, on which each module could function independently of the others, none of the ISS modules can survive in space without the assistance of the others. In this regard, aerospace engineers liken the ISS design to the human body, in which each of the body's systems has a distinct and highly specialized function yet each is dependent upon the proper functioning of all others.

Such a design will make possible more complex experiments that will answer more questions about

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