Don't rule out another space shuttle flight this year.

NASA administrator Michael Griffin said Friday he hasn't given up on that goal, even though future shuttle flights are grounded for now.

NASA said Wednesday it won't fly another shuttle until it solves the problem of debris breaking off of the shuttle's external fuel tank during launch.

Griffin says he's set up a "tiger team" to solve the problem as quickly as possible. As he put it, "We don't expect this to be a long, drawn-out affair."

Griffin joined other NASA officials in saying it was a mistake to not solve the fuel tank problem before Discovery took off.

NASA's John Shannon said a detailed study of the shuttle's hull has turned up "25 small dings." The flight operations official said that compares to 150 dings on a typical mission. He said Discovery is "extremely clean."

Earlier, the spacecraft's commander said she isn't ready to give up on the space program.

Commander Eileen Collins said from orbit Friday she was surprised that a piece of foam broke off the shuttle's external tank during Tuesday's liftoff.

Collins said she thought "we had that licked."

But Collins said the problem can and must be fixed. She agrees with NASA officials that there shouldn't be another shuttle flight until NASA takes care of the shedding problem. But she said she is not ready to give up on future shuttle flights.

Friday's Activities

Discovery's astronauts spent Friday morning unloading 15 tons of supplies onto the international space station.

Later, they plan to check the shuttle for damage. NASA now says a smaller piece of foam may have hit a wing during liftoff.

NASA officials say Discovery looks safe to fly home in a week, but they say they won't know for sure for a couple of days.

Astronauts are also preparing tools for the mission's first spacewalk Saturday. During the extra-vehicular activity, astronauts will try out new repair techniques for the shuttle's tiles and delicate carbon panels, replace a gyroscope that helps steer the space station and install a storage platform on the station.

NASA also says it's trying to come up with ways to leave more water and oxygen aboard the space station than initially planned.

A chunk of insulating foam from the external fuel tank is blamed for the destruction of shuttle Columbia more than two years ago. It cracked the leading edge of one of the craft's wings, letting in superhot gases during re-entry.

A redesigned fuel tank was supposed to solve the problem.