The optimism that blasted off along with Tuesday’s successful launch of the space shuttle was grounded – along with the rest of the fleet – after scientists examined the data from liftoff.

Debris flying from the external fuel tanks still pose a significant risk to Discovery and its crew. Only luck, they said, prevented the type of damage that destroyed the Columbia 2 1/2 years ago. NASA says the ship escaped serious damage, although astronauts will recheck part of the heat shielding to make sure.

The aging shuttle program, an engineering marvel even if it has never lived up to expectations of a quickly reusable space vehicle, could be finished. NASA had planned to retire the space shuttle fleet by the end of the decade, even though its replacement, the Crew Exploration Vehicle, isn’t scheduled to fly until 2014. More immediately, the planned launch of the shuttle Atlantis in September is in jeopardy.

Unless NASA is able to resolve the problems that have grounded its fleet, the United States could find itself without a means to put a person in space, ceding that strategic and scientific field to other countries. With the money that has been spent, the space shuttle’s safety and usefulness must be questioned.

Space still has much to teach us. The education can continue with unmanned exploration, which has recently produced inspiring results. From the twin Mars rovers to Deep Impact, which successfully collided with a comet, the United States’ space program has shown its technological muscle.

But it is the flight of men and women beyond our own world that captures the imagination and inspires the country to fulfill its obligation to explore. Without the ability to put an astronaut into space, we fear that support for the space program will stagnate.