It used to be the envy of the neighborhood. But now, 25 years after you first took it out for a spin, people just shake their heads on the rare occasions when you get it out of the garage.

It really hasn't been cared for or serviced as it should be. The only reason to start the old buggy is to prove you can start it.

Driving down the road, all your attention has to be focused on making sure some important pieces haven't fallen off. And that summer home you're building in the mountains, the one your old car can barely get you to, is only about half finished after years of work.

Tell that story again, only this time about the whole nation, and you've got the sad history of the American space shuttle program.

Tuesday's successful launch of the shuttle Discovery - another in a series of events NASA labels "return to flight" - was replete with Independence Day imagery and American can-do spirit. But, admit it, the primary focus of public interest in space flight these days is dreading that the next shuttle will blow up, either on re-entry, as happened to Columbia three years ago, or during its blazing lift-off, as was the case with Challenger all the way back in 1986.

The official purpose of this mission, other than going over the orbiter's every inch with cameras and sensors, is to visit the International Space Station. That's the half-finished project that will remain that way unless NASA can successfully launch 17 more shuttle missions before the whole fleet is scheduled to be retired just four years from now.

Seeing that the current flight was launched over the safety objections of some of NASA's own engineers, the possibility of achieving such an ambitious schedule seems low. And the pressure to cut corners in the attempt seems unacceptably high.

Space flight always has been, and always will be, risky. But risks should have a purpose, a purpose other than deadlines and schedules and political considerations.

And when the primary purposes of space flight, science and discovery can be better accomplished with no risk to human life and a lot less money by using robots in place of people, it once again seems clear that it is well past time for the shuttle program to be retired.