In 1993, after a long consideration, NASA agreed to accept Russia into an exclusive club of Western countries developing a multi-module space station known as Freedom. By that time the project -- announced by the Reagan administration in 1984 as the next "logical step" after the space shuttle program -- went through numerous redesigns and lagged almost a decade behind the originally proposed launch date.

Russian participation promised to save development costs for critical components of the station, as well as almost double the outpost's habitable volume and eliminate its total dependence on the delay-prone space shuttle fleet.

The Zvezda service module would become the first element of the station financed entirely by the Russian government. Not surprisingly, as the initial launch date for the module neared -- April 1998 -- the economic situation in Russia worsened. By the mid 1990s the spacecraft fell behind schedule.

Here are the major milestones in the module's long road to the launch pad:

• Fall 1996: Russia officially informs NASA that the service module will not be ready for launch in April 1998 due to funding problems. As a result, the launch of the first component of the ISS, named the Zarya control module, slips from the original date of November 1997.
• December 1996: After evaluating several options, NASA decides to develop the interim control module (ICM) which would act as a temporary propulsion unit for the outpost should Russia fail to deliver the service module.
• May 1997: After reviewing the program, the partners officially delay the launch of the first element from November 1997 to June 1998 and the service module until November 1998.
• June 1998: The partners in the ISS project agree to reschedule the launch of the service module to December 1998.
• October 1998: NASA and the Russian Space Agency agree to launch first element of the station in November 1998. The launch of the service module at that time was scheduled for April 1999 but was expected to be delayed by funding problems until June.
• November 1998: Russian Proton rocket successfully launches the Zarya control module, the first element of the ISS; at the time, the launch of the service module is expected in July 1999.
• December 1998: The space shuttle launches and docks the U.S.' Unity module to Zarya.
• April 1999: NASA and Russian officials agree to delay the Zvezda service module launch until some time between September 20 and November 20, 1999
• May 1999: Zvezda is shipped to Baikonur for the final prelaunch processing. The launch is officially scheduled for fall 1999. If successful, the first residential crew would be able to inhabit the ISS in early 2000.
• June 1999: The space shuttle visits ISS on a resupply mission. At the time, the launch of the service module is expected between November 12 and 20, 1999.
• August 1999: The wiring problems on the space shuttle fleet force NASA to consider delaying Zvezda's launch until December-January 2000.
• October 1999: NASA and the Russian Aviation and Space Agency agree to delay the service module's launch from November to at least December 26, but more likely until January 2000.
• October 1999: A Russian Proton rocket carrying a communications satellite fails for the second time in 1999.
• January 2000: The Proton crash investigation concludes with the decision to use modified engines on the second and third stages of the rocket that will carry Zvezda. It is also decided that two or three rockets have to fly successfully before Zvezda's launch is attempted.
• February 2000: Reacting to Russia's decision to reactivate their Mir space station, NASA decides to launch the interim control module (ICM) to the ISS in 2001, even if the service module is successfully linked to the station. NASA claims that unless Russia orbits Zvezda in 2000, it will launch the ICM in December of that year. In reality, the ICM's own delays make a 2000 launch impossible. NASA also demands that Russia deliver the service module by August 2000 or face possible expulsion from the project. Russian officials respond that Zvezda might go up as early as June, but more likely in July 2000.
• February 2000: The Proton returns to flight. The development of the modified upper-stage engines is expected to be completed by May 2000. The launch of the service module is expected between June and August 2000.
• June 6, 2000: The first Proton rocket with modified engines successfully delivers a communications satellite in orbit.