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flying, and explored international cooperative space projects as a means of filling in for a permanent station.

The U.S. invited Europe to participate in its post-Apollo programs in 1969. In August 1973, Europe formally agreed to supply NASA with Spacelab modules, mini- laboratories that ride in the space shuttle’s payload bay. Spacelab provides experiment facilities to researchers from many countries for nearly three weeks at a time–an interim space station capability. Spacelab 1 reached orbit in 1983, on the ninth space shuttle flight (STS-9). The main European contributions to International Space Station, a laboratory module and a supply module, are based on Spacelab experience and technology.

  • U.

    S. and Soviet negotiators discussed the possibility of a

  • U.

    S. Space Shuttle docking with a Soviet Salyut space

station. This was an outgrowth of the last major U.S.- Russian joint space project, Apollo-Soyuz, the first international spacecraft docking in 1975. The Space Shuttle’s ability to haul things down from space complimented Salyut’s ability to produce experiment samples and industrial products–things one would want to return to Earth. NASA offered the Space Shuttle for carrying crews and cargo to and from Salyut stations and in return hoped to conduct long-term research on the Salyuts until it could build its own station, but these efforts ended with the collapse of U.S.-Soviet detente in 1979.

By 1979, development of the Space Shuttle was well advanced. NASA and contractor engineers began conceptual studies of a space station that could be carried into orbit in pieces by the Space Shuttle. The Space Operations Center was designed to serve as a laboratory, a satellite servicing center, and a construction site for large space structures. The Space Operations Center studies helped define NASA expectations for a space station.

The Space Shuttle flew for the first time in April 1981, and once again a space station was heralded as the next logical step for the U.S. in space. NASA founded the Space Station Task Force in May 1982, which proposed international participation in the station’s development, construction, and operations. In 1983, NASA held the first workshop for potential space station users.

These efforts culminated in January 1984, when President Ronald Reagan called for a space station in his State of the Union address. He said that the space station program was to include participation by U.S. allies.

With the presidential mandate in place, NASA set up the Space Station Program Office in April 1984, and issued a Request for Proposal to U.S. industry in September 1984. In April 1985, NASA let contracts on four work packages,

each involving a different mix of contractors and managed by a separate NASA field center. (This was consolidated into three work packages in 1991.)

This marked the start of Space Station Phase B development, which aimed at defining the station’s shape. By March 1986, the baseline design was the dual keel, a rectangular framework with a truss across the middle for holding the station’s living and working modules and solar arrays.

By the spring of 1985, Japan, Canada, and the European Space Agency each signed a bilateral memorandum of understanding with the U.S. for participation in the space station project. In May 1985, NASA held the first space station international user workshop in Copenhagen, Denmark. By mid-1986, the partners reached agreement on their respective hardware contributions. Canada would build a remote manipulator system similar to the one it had built for the space shuttle, while Japan and Europe would each contribute laboratory modules. Formal agreements were signed in September 1988. These partners’ contributions remain generally unchanged for the International Space Station.

In 1987, the dual keel configuration was revised to take into account a reduced space shuttle flight rate in the wake of the Challenger accident. The revised baseline had a single truss with the built-in option to upgrade to the dual keel design. The need for a space station lifeboat–called the assured crew return vehicle–was also identified.

In 1988, Reagan gave the station a name–Freedom. Space Station Freedom’s design underwent modifications with each annual budget cycle as Congress called for its cost to be reduced. The truss was shortened and the U.S. Habitation and Laboratory modules reduced in size. The truss was to be launched in sections with subsystems already in place. Despite the redesigns, NASA and contractors produced a substantial amount of hardware. In 1992, in moves presaging the current increased cooperation between the U.S. and Russia, the U.S. agreed to buy Russian Soyuz vehicles to serve as Freedom’s lifeboats (these are now known as Soyuz crew transfer vehicles) and the Shuttle-Mir Program got its start.

In 1993, President William Clinton called for the station to be redesigned once again to reduce costs and include more international involvement. To stimulate innovation, teams from different NASA centers competed to develop three distinct station redesign options. The White House selected the option dubbed Alpha.

In its new form, the station uses 75 percent of the hardware designs originally intended for the Freedom program. After the Russians agreed to supply major hardware elements, many originally intended for their Mir 2 space station program, the station became known as the International Space Station. Russian participation reduces

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