The concept of an international space station can be traced back to the mid-1800s when U.S. clergyman Edward Everett Hale wrote of a polar-orbiting satellite, built from 12 million bricks, to serve as a navigation aid for ships at sea. Written in 1869 for The Atlantic Monthly, the appropriately titled “The Brick Moon,” was a short novel about a group of determined young New Englanders who constructed a 200-foot (61-meter)-diameter brick sphere, capable of carrying 37 passengers, catapulted into a 4,000-mile (6,437-kilometer)-high orbit by a pair of massive flywheels.

Transylvanian mathematics teacher Hermann Oberth's revolutionary 1923 treatise, The Rocket into Interplanetary Space, was filled with calculations on rocketry and even a design for a 115-foot (35-meter)-tall bullet-shaped rocket with four large fins. Oberth conceptualized a human expedition to Mars with an orbiting refuelling station (or weltraumstation) to be used as a staging point for the voyage.

Austrian engineer Hermann Noordung wrote in 1929 of an orbiting space station, shaped like a giant wheel that slowly rotated to produce artificial gravity. Noordung's concept used solar mirrors to direct sunlight to power a steam turbine that generated electrical power for the station.

One of Oberth's students, Wernher von Braun, was placed in charge of developing rockets into military weapons for use by the German army in 1932. Von Braun viewed the development of a large ballistic missile as simply an intermediate step for his grander vision of a human Mars expedition. Unfortunately, Adolf Hitler had more sinister plans for von Braun's rocket, named the V-2, turning it into a terror weapon fired against civilian populations in London and other European cities, inflicting many thousands of casualties.

During the final days of World War II, von Braun and about 120 members of his rocket team surrendered to the advancing American army and were relocated to the United States. While continuing his work on rockets, von Braun became a vocal and visible advocate for space travel.

A widely read series of von Braun-authored articles on space projects such as large rockets, lunar missions, and an orbiting space station appeared in the popular Colliers magazine beginning in March 1952, accompanied by fanciful illustrations by space artist Chesley Bonestall. Von Braun appeared on the cover of Time magazine and served as technical advisor on a 1955 Walt Disney television program, Man and the Moon, which featured the evocative images of a wheel-like space station serving as the launching point for a mission to the Moon.

 
Space Station Freedom Option A showing two Soyuz Assured Crew Return Vehicle (ACRV) capsules docked at berthing ports.

Von Braun's vision of an orbital space station was generally acknowledged as the best “building block” to support a wide range of space activities, but President John Kennedy's bold (and unexpected) decision to land American astronauts on the Moon before 1970 required a total commitment from the government/industry team. The Moon landing project did not exclude the construction of a space station; however; there simply was not enough time or money to build one in the short term.

In the early 1960s, the National Aeronautics and Space Administration (NASA) continued to investigate a variety of post-Apollo space station concepts, though they remained low on the agency's priority list for funding and resources. In 1964, contracts were awarded for the design of a Manned Orbital Research Laboratory (MORL), an approximately 30,000-pound (13,608-kilogram) space station to be lifted by a Saturn 1B rocket with crews launched in either a Gemini or Apollo spacecraft.

Somewhat lost in the shadow of the Gemini program and the upcoming Apollo Moon landings, a Saturn-Apollo Applications Program Office was established on August 6, 1965. Two potential projects were carefully considered. The first, the Orbital Workshop (OWS) concept of a space station, would be created by using the spent upper stage of a Saturn 1B rocket. The second, the Apollo Telescope Mount, would integrate a solar telescope into the frame of a free-flying Apollo Lunar Module.

The U.S. Air Force, not directly involved in Project Apollo, envisioned a crewed space station as a valuable military asset for orbital reconnaissance missions. After the 1963 cancellation of its winged space plane, the X-20 Dyna-Soar, the Air Force shifted its focus to the development of the Manned Orbiting Laboratory (MOL)-a house-trailer-size laboratory to be launched into orbit atop a Titan 3 booster along with a modified Gemini spacecraft carrying two military astronauts for missions lasting up to 30 days.

Originally targeted for a 1968 launch, the MOL program experienced significant cost overruns and schedule delays with the first mission slipping into 1969, and then to 1972. Remarkable advances in un-crewed reconnaissance satellite systems soon rendered MOL's primary mission obsolete and, on June 10, 1969, President Richard Nixon cancelled the program.

The Apollo Applications Program continued to quietly evolve. The Orbital Workshop and Apollo Telescope Mount projects were combined into a design for a house-sized orbiting space station outfitted into the third stage of a Saturn 5 moon rocket (originally built for the cancelled Apollo 20 mission) and officially renamed “Skylab.”

Launched on May 14, 1973, Skylab became the United States' first orbiting space station. Weighing almost 200,000 pounds (90,718 kilograms), Skylab contained a two-level workshop (including crew living quarters), a docking adapter and airlock, and the Apollo Telescope Mount. Three separate teams of astronauts lived and worked on Skylab for a total of 171 days in 1973 and 1974.

Plans for a reusable “space shuttle” to affordably transport crews and supplies to a permanent orbiting space station were NASA's immediate post-Apollo priority; however, Congress was unwilling to fund such an ambitious effort and approved only the construction of a Space Shuttle in 1972. Following the first successful Shuttle missions in 1981 and 1982, NASA again revived the notion of an orbiting laboratory and created the Space Station Task Force in May 1982 to define mission requirements and a preliminary design concept.

President Ronald Reagan, anxious to project American dominance in space technology, announced the construction, within a decade, of an $8-billion permanently crewed space station in his 1984 State of the Union Address, stressing that NASA would invite international participation in the endeavour. Eleven nations (Japan, Canada, and nine nations of the European Space Agency) signed a formal agreement with NASA on September 28, 1988, to participate in the program, renamed by President Reagan as “Space Station Freedom.”

Unfortunately, Freedom's escalating costs combined with congressional budget cuts slipped the Station's first launch date to March 1995, a year later than planned. The international partners were unhappy because they had not been consulted about the schedule delays as well as a one-third reduction in the amount of electrical power available for all Station users. Freedom's weight continued to grow, forcing NASA to start developing new Shuttle Solid Rocket Boosters to lift the heavier components, while the Station's price tag more than doubled to $19 billion.

By October 1990, Space Station Freedom found itself in the same untenable position as the ill-fated Manned Orbiting Laboratory-overweight, over budget and behind schedule. Congress slashed funding and demanded a complete redesign of the space station project, with the emphasis on affordability.

Following the 1991 collapse of the Soviet Union, NASA was again directed in 1993 to cut Freedom's cost and complexity, maximize the Station's scientific capabilities and leverage Russia's considerable experience in space station operations, exemplified by Salyut and Mir, by inviting its participation in the project. A series of nine joint U.S.-Russian missions involving the Space Shuttle and the Mir Space Station from 1994 to 1998 provided valuable experience in docking, orbital operations and the ability to manage a multinational program.

The redesigned orbital laboratory is now known as the International Space Station (ISS). Sixteen nations are participating in its design, construction and operations.

The ISS design consists of a bridge-like linear truss framework, with laboratories, living quarters, water and power generating systems, and multiple docking ports with an airlock for spacewalks. Planned major components of the ISS will include: United States Laboratory

Module, Joint Airlock and Solar Power Array; European Space Agency Columbus Orbital Facility; Japanese Experiment Module with Centrifuge Facility; Russian Service and Research Modules; and a Canadian Mobile Servicing System (Canadarm 2).

Station construction will require more than 40 launches involving United States' Space Shuttles and Russian Soyuz and Proton rockets to deliver the more than 100 ISS components to orbit, followed by thousands of hours of spacewalks by astronauts and the use of robotic technology to assemble these components. Seventeen flights, including 13 Space Shuttle missions, have already occurred in the ISS construction sequence.

The first ISS flight occurred in November 1998 when a Russian Proton rocket lifted off, placing the Russian built/U.S. financed Zarya (Sunrise) control module in orbit, followed a month later by the Shuttle Endeavour on mission STS-88 carrying the Unity connecting module. The Unity and Zarya segments were attached using the Shuttle's robotic arm, then spacewalking astronauts made the required connections between the two.

The Russian Zvezda Service Module, providing the Station with life support equipment and docking ports, was launched into orbit by an un-crewed Russian Proton rocket on July 25, 1999. Ground controllers remotely docked Zvezda to the orbiting Unity/Zarya combination.

Shuttle Discovery on the STS-92 mission in October 2000 carried the Z1 Truss, Pressurized Mating Adapter 3 and four Control Moment Gyros to the ISS, followed two months later by Shuttle Endeavour on mission STS-97 which installed the first set of U.S. solar power arrays.

Shuttle Atlantis on mission STS-98 in February 2001 transported the U.S. Destiny Laboratory Module to the orbiting outpost and its astronauts relocated the Pressurized Mating Adapter 2 from the end of Unity to the end of Destiny to set the stage for future Shuttle missions.

In March 2001, Shuttle Discovery on mission STS-102 carried Leonardo, the first reusable cargo container or Multi-Purpose Logistics Module, built by the Italian Space Agency, to the Station complex. The following month, Shuttle Endeavour on mission on STS-100 delivered the Canadian robotic arm (Canadarm 2), also known as the Space Station Remote Manipulator System, and the second Italian Multi-Purpose Logistics Module, named Raffaello.

The Space Station's joint airlock, named Quest, was installed by the crew of Shuttle Atlantis on mission STS-104 in July 2001, followed in September 2001 by the launch of an un-crewed Russian Soyuz rocket with the Russian Pirs Docking Compartment 1 and the Strela boom. The crew of Shuttle Atlantis on mission STS-110 in April 2002, carried the Station's “backbone”, known as the S-0 Truss, the first segment of a nine-piece Integrated Truss Structure, and the Mobile Transporter, a movable “railway” to transport the Station's Canadian robotic arm.

When the ISS is fully assembled (projected for 2004), the orbital complex will weigh almost a million pounds (453,592 kilograms), stretch 356 feet wide and 290 feet long (109 by 88 meters), wider and almost as long as an American football field, and support up to seven astronauts in a shirtsleeve environment encompassing 46,000 cubic feet (1,303 cubic meters)-roughly the equivalent of two Boeing 747 jetliners.