Editor's Note: NASA's estimate for making the repairs necessary to return the space shuttle fleet to flight operations in 2005 remains $1.1 billion to $1.45 billion. The $2.2 billion figure cited during the Aug. 8 hearing, and discussed in this article, is what NASA expects to spend on space shuttle safety improvements through 2008.

WASHINGTON (AP) _ NASA administrator Sean O'Keefe said Wednesday the cost of fixing all the problems with the space shuttle fleet could top $2.2 billion -- double the estimated price tag given to Congress a year ago.

O'Keefe, testifying before the Senate Commerce, Science and Transportation Committee, was pressed on whether that estimate again could rise.

Sen. Sam Brownback, R-Kan., who chaired the panel, noted that the space agency still had 10 items left on 15 required improvements it must complete before shuttles again can fly. Brownback asked O'Keefe whether the agency had confidence in the higher estimate.

"We're getting a lot closer, that's for sure," O'Keefe said. "I don't see any new unknowns coming down the road."

Thomas P. Stafford, co-chairman of a task force monitoring the space agency's progress in meeting the new safety requirements, said he expected NASA would earn at least conditional approval on the remaining 10 items by the end of 2004.

The space shuttle fleet has been grounded since Feb. 1, 2003, when the shuttle Columbia broke apart over Texas, killing all seven astronauts.

O'Keefe said it was not clear whether damage to Kennedy Space Center from Hurricane Frances would result in a delay of the anticipated launch next spring of Discovery. NASA disaster response teams are completing an inventory of damaged facilities.

Flipping through oversized, color images, NASA officials pointed to hundreds of missing panels from an Apollo-era hangar where pre-launch assembly of shuttles should occur.

Sen. Bill Nelson, D-Fla., put the number of missing panels at 1,000; NASA officials had said Tuesday there were about 820, with about one-quarter of them punched all the way through.

Nelson said those represent an open window through which damaging wind and rains from Hurricane Ivan, the next brewing storm, could pass.

Nelson counseled O'Keefe to be speedy with the agency's repair estimate and to include the cost of building a structure that could withstand higher-force winds. The damaged building was designed to withstand gusts up to 125 mph, while a direct blow by a category 4 hurricane could yield 145 mph winds.

The damage, Nelson said, underscored the folly of the space agency's raiding its maintenance budget to make up for federal funds that have not kept pace with its needs.

"NASA has been robbing Peter to pay Paul because NASA has not had the increases that it has needed to do an ambitious space program," Nelson said. "And you can't do space flight on the cheap."