About halfway through a three-year program to fly NASA astronauts on Mir a funny thing happened: The Americans stopped being guest researchers and became key members of their crews. It took a series of emergencies for the transition to occur and certainly was not what NASA and the Russian Space Agency had in mind when they hammered out plans to meld their human spaceflight programs.

Norm Thagard, a former Vietnam fighter pilot, physician and long-time astronaut, was the first to live on Mir. His 3 1/2-month mission, which began in March 1995, was an exercise in patience and endurance. A stickler for details, Thagard stubbornly refused to eat any food that was not properly bar-coded, as mandated by a hastily prepared science program that included medical studies. A lot of the food ended up reaching Mir without the required labels, so Thagard didnt eat it. As a result, he dropped an alarming 17 pounds from his already wiry frame.

With much of his scientific gear stranded on the ground, Thagard also fought off boredom during much of his flight. When he returned to Earth aboard the space shuttle, Thagards first step was one of defiance. Against doctors wishes, he got up out of his reclined chair, stood and then crawled out on his own accord.

NASA Administrator Daniel Goldin publically apologized to Thagard for a lack of support and presented him and his Russian crewmates with a welcome home treat of ice cream and hot dogs. (Ever practical, Thagard ate his ice cream first so it wouldnt melt. When he looked around for a hot dog, they had already been taken away.)

Thagard left NASA at the end of that year, returning to his alma mater, Florida State University, to teach. He also has been spending his time developing a Challenger Learning Center in Tallahassee to expose middle-school children to science, engineering and mathematics.

After Thagards flight, six more NASA astronauts lived on Mir between March 1996 and June 1998. Shannon Lucid, the only U.S. woman to make a long-duration mission on Mir, and John Blaha, the only shuttle commander among NASA-Mir astronauts, had relatively easier times aboard the space station largely because of changes made after Thagards pathfinder mission.

Lucid, an outgoing, motherly woman with two grown daughters, flourished during her six-month stay, a mission that ran two months longer than planned because of delays launching the shuttle that would bring her home. She liked working in her laboratory and got along well with her crewmates, although she never mastered the Russian language. Lucid stayed with NASA and today is working to prepare crews and their trainers for long-duration flights on the International Space Station.

Blahas four-month mission had a rough start. The crew he had trained with in Russia was removed from the flight just before they were set to launch. Doctors said the commander had a possible heart condition, discovered during the final prelaunch physical.

Blaha battled depression in orbit, finally mastering the situation by blocking out all thoughts of his wife, Brenda, and their family and friends. "I had to work at forgetting Brenda and when I did that then I loved being on the station," he said after his flight.

Blaha left NASA to become an executive with USAA, a multi-billion dollar insurance and financial services conglomerate, based in San Antonio, Texas. Blaha now keeps track of Mirs whereabouts through the internet so he knows when it is passing over Texas.

"My wife and I sit out in our hot tub quite a bit and we enjoy sitting out there when the Mir is going to fly by. Ive always enjoyed watching it fly by because we know people are still on it. But one of these days it wont be there, and starting Friday there wont people on it anymore so it wont be as exciting."

Like Thagard, Blaha also is working to open another Challenger Learning Center for science education.

A young Navy doctor, Jerry Linenger, took over Blahas post on Mir. He had been hurriedly flown on a single space shuttle mission to fulfill Russian requirements that the Mir astronauts be experienced. He began his flight with enthusiam, despite the fact that he was leaving behind a year-old son and a pregnant wife.

During his stay in orbit, a defective Russian oxygen candle triggered a dangerous fire that cut off one of the escape routes to the Soyuz spaceships, which would be used to take the crew home in an emergency. NASA managers did not immediately learn of the fire.

Linenger returned home convinced the station was not a viable place for serious scientific research and quit the astronaut corps. He now lives in Michigan and runs his own company called Linenger Communications.

NASA began pressing the Russians for more day-to-day technical information about the station, a job that became much easier after the next crisis. Linengers replacement , Michael Foale, a well-liked, British-born astronaut, was aboard Mir on June 25, 1997, when a remotely piloted cargo ship crashed into the station, puncturing its hull. Foale, who had been sent away into the Soyuz to await an emergency departure, floated back into Mir to assist his two crewmates who were frantically trying to seal off the damaged Spektr module.

In crisis, budding Russian-American friendships blossomed, both in space and on Earth. NASA was able to fight off Congressional critics who called for an end to the shuttle-Mir program.

Two more astronauts flew to Mir, David Wolf and Andrew Thomas. Their flights passed relatively smoothly and NASA began turning its attention to launching the first pieces of the International Space Station.

Foale, Wolf and Thomas have all stayed with NASA. Foale is scheduled to fly on the upcoming shuttle mission to service the Hubble Space Telescope. Wolf and Thomas, like Lucid, are training future space station crews.

"Its kind of sad that this place where you live in is going to be gone," said Wolf. "But there comes a time when you move on."