After two years of frustrating setbacks and delays, NASA officially set July 13 as the launch date Thursday for the first space shuttle flight since the Columbia tragedy.

NASA Administrator Michael Griffin announced the news after a two-day space agency review of Discovery's readiness to blast off.

"Based on a very thorough and very successful flight readiness review, we're currently `go' for launch of Discovery on July 13," Griffin said.

Earlier in the week, an advisory panel concluded that NASA failed to meet three of the 15 safety recommendations issued by the Columbia accident investigators in 2003. Despite many improvements, the shuttle is still vulnerable to pieces of foam or ice falling off the external fuel at liftoff, and the astronauts still have no reliable way of fixing damage to their ship's thermal shielding once in orbit, the group said.

But Griffin and others at NASA believe those risks have been reduced to an acceptable level.

A large chunk of fuel-tank insulating foam smashed a hole in Columbia's left wing during liftoff in January 2003 and caused the shuttle to break apart during re-entry two weeks later. All seven astronauts were killed.

NASA's main focus following the accident was on keeping big pieces of foam from falling off the fuel tank. It was not until this past spring that engineers fully realized the dangers posed by ice, which can form on the tank once the super-chilled fuel is loaded and can fall off during launch. That realization prompted NASA to delay the mission from May to July and install another heater on the redesigned tank.

Discovery will carry seven astronauts to the international space station, along with sorely needed supplies and replacement parts. If Discovery suffers irreparable damage en route, the astronauts will move into the station and await a rescue by Atlantis — a situation NASA considers an extreme last resort.

(Chinadaily.com July 1, 2005)