Russia's orbiting outpost in space has ensured its place in the history of human space flight. Now it's time to shut the air locks and focus on the next generation space station.
That's the view of some US space analysts, who argue that any additional benefits from sending two more American astronauts to the troubled Mir space station don't warrant the risk involved.
The latest mishap on Mir, the failure of the on-board computer, was fixed Tuesday by replacing hardware. Despite the quick resolution, it only served to fuel debate over the ongoing value of Mir. Life on the orbiting space station has become less a mission of science or engineering and increasingly one of survival.
In the past eight months, a fire, a series of highly publicized mechanical failures, and a collision between an unmanned Russian cargo capsule and the station's Spektr module have fueled doubts about the aging station's safety and the need for additional US crew members.
"There are real questions about the added value of two more flights," says Marcia Smith, a space-policy analyst at the Library of Congress. Since 1995, five astronauts have called Mir home for periods of up to five months. What they bring back, insists the National Aeronautics and Space Administration (NASA), is valuable experience that can be applied to the International Space Station, scheduled for launch next June. NASA is paying the Russians $473 million for use of Mir from 1995 through mid-1998.
NASA officials are in Moscow now to meet with their counterparts to review Mir's status. On Sept. 25, the shuttle Atlantis is scheduled to launch, bringing up supplies and repair gear, including a sealant to repair Mir's hull. During the flight, astronaut David Wolf will replace Michael Foale aboard the station. Nearly everyone - especially NASA officials - agrees that up to now, having a US crew member aboard Mir has been valuable.
"I was not excited about this in the beginning," says John Charles, NASA's mission scientist supervising the Mir experiments by Jerry Leninger and Dr. Foale. "But I can now say with complete honesty: Thank goodness for the shuttle-Mir program."
THE payoffs, he says, are biggest for engineers studying such issues as spacecraft corrosion, and for people preparing for the construction and operation of the international space station. As for scientific benefits, out of four goals for this phase of the Mir program, "we're fourth on the list," he concedes.
Still, he says, Mir flights have helped physiologists understand how humans adapt to long periods of weightlessness. Experiments with wheat and beetles have highlighted the role of gravity in plant growth and in setting an organism's "biological clock." Biotech experiments are helping to "design" new medications.
Skeptics agree the US should continue Mir resupply missions. But from the standpoint of scientific research, the station lost half its science equipment when Spektr was put out of commission. "NASA says it can fill 80 percent of Wolf's science schedule, but even they say that alone doesn't justify having him up. They say the operational experience is useful," Smith says. "We would learn how to cope with operational surprises. But it's not clear how directly applicable that is to the International Space Station."
"We're not going to fly the International Space Station three times longer than its design life," adds James Oberg, an expert on the Russian program. "And to say that the Russians have some unique ability to respond to emergencies in space is an insult to a generation of American space engineers" who have coped with everything from the near-disastrous Apollo 13 mission to delicate on-orbit repairs to the Hubble Space Telescope.
Mir has fulfilled its mission, Mr. Oberg says, as the first semipermanent outpost in space. Its legacy is as "a theater for people to live and work" for up to 14 months and return to Earth healthy - a vital consideration for future missions to the moon or Mars.