NASA experts announced Thursday they had corrected flaws that caused the destruction of the space shuttle Columbia in February 2003. Redesigned space shuttle fuel tanks will no longer shed potentially dangerous insulating foam during launch. A modified shuttle will be ready to resume flights next Spring.

Last year a chunk of the foam damaged a wing of the Columbia, leading to the breakup of the shuttle high over Texas.

NASA is aiming for three shuttle flights in 2005.

The tank will no longer have thick foam insulation on the spot where it tore off Columbia at liftoff. New heaters will be there instead, to prevent ice buildup when the tank is filled with super-cold fuel.

As engineers looked into the shuttle system, they found many other things that needed fixing, validating the board's concerns, and took time to do them.

So far, NASA has complied with five of the 15 return-to-flight recommendations set forth by the Columbia Accident Investigation Board on Aug. 26, 2003. The remaining 10 must be completed by December for NASA to launch Discovery to the international space station by mid-March to mid-April, the space agency's goal.

If preparations stay on schedule, the shuttle Discovery is to take off between March 16 and April 18. Although the shuttle is to carry supplies to the International Space Station, the flight will be seen as a test of the changes in the spacecraft and its operation. Astronauts will not resume construction of the station until a third flight.