Hurricane Frances battered the Kennedy Space Center, a top NASA official said Tuesday, blowing gaping holes in the Vehicle Assembly Building and ripping open the roof of a facility needed for the space shuttle's return to flight.

While NASA's three shuttles and costly components awaiting launch to the international space station escaped damage, repairs to the spaceport's infrastructure could delay the first post-Columbia flight, targeted for March.

"I'm not going to estimate when we might return to flight," the center's director, James W. Kennedy, told reporters Tuesday after surveying the damage. "It's very much to be determined the impact that the facility damage will have on our ability to return to flight."

The spaceport was shut down Thursday and its 14,000-member workforce sent home to prepare for Frances. Before they left, engineers closed each shuttle's cargo bay doors, raised the landing gear and shored up hangar doors and windows with sandbags and plywood panels.

The three orbiter processing facility hangars were designed to withstand 105-mph winds while the Vehicle Assembly Building (VAB), built in the early 1960s and now used to assemble shuttles for launch, was built to withstand gusts of up to 125 mph.

But no major hurricane has ever hit the space center and engineers did not know what to expect from Frances, which delivered torrential rain, sustained winds of more than 70 mph and gusts of up to 94 mph when it roared through Brevard County on Saturday and Sunday.

On Tuesday, after a helicopter survey of the sprawling spaceport, a clearly relieved Kennedy said NASA's multibillion-dollar orbiter fleet survived its weekend brush with Frances intact, as did flight hardware at the space station processing facility. But the storm did not let the nation's manned space program off lightly.

Frances clobbered the VAB, ripping off about 820 metal siding panels measuring 4-by-16 feet each, covering nearly 52,500 square feet. About 20 percent of that area included subsurface insulation panels, leaving the interior open to the elements.

The only flight hardware inside the building at the time were two shuttle external fuel tanks and a handful of solid-fuel booster components. All escaped damage.

But a 30-member team inspecting the roof of the building had to make a hasty retreat when it became obvious "it was very insecure, it was soggy, it was weak and they did not want to run the risk of falling through the roof," Kennedy said.

Netting is now hung below the roof to catch debris that might fall until repairs can be made. In the meantime, the VAB damage is a major concern with another hurricane -- Ivan -- on a potential collision course with Florida.

"The facilities engineering people today don't think that between now and the possible arrival of Ivan as early as next Saturday there is anything they can do to plug those holes," Kennedy said. "So we will probably be, for the next period of time, including Ivan if she comes ashore, sitting there with an open window to the world in the VAB."

Nearby, a building used to manufacture heat-shield tiles and protective thermal blankets for the shuttle fleet lost a quarter of its roof and suffered major water damage. The facility is critical to NASA's return-to-flight effort, and engineers are looking into whether the tile work can be temporarily transferred back to Palmdale, Calif., where the shuttles were originally built, or moved to Houston until repairs are made.

Hurricane Charley caused about $700,000 in damage to the space center last month when it moved across central Florida.

Kennedy said he had no idea what it might cost to recover from Frances, but it is "going to be significantly more than that."

"I have no question that the VAB can be rebuilt to where it will safely and securely process shuttle hardware," he said. "The big unknown is: What will it take to make the VAB safe and secure again?"

Last week, Kennedy worried that a direct hit from Frances, then a Category 3 hurricane with winds gusting to 140 mph, could spell the end of the nation's manned space program. As it turned out, that scenario did not play out. This time.

Workers at the Kennedy Space Center remove hurricane debris from the Vehicle Assembly Building.