We are now three and a half years and hundreds of millions of dollars later than the Columbia accident and NASA still faces the same vexing foam problem.
Insulation foam -- it seems a trivial part of launching a complex spacecraft. But the problem of falling foam has perplexed the U.S. space agency capable of doing what no other country does, landing a space freighter like an airplane.
Outfitted with a second round of upgrades to its fuel tank following the 2003 Columbia disaster, Discovery is on the launch pad and scheduled to fly at 3:49 p.m. EDT (1949 GMT) on July 1.
If successful, NASA plans up to 17 more shuttle missions, including a possible servicing call to the Hubble Space Telescope, before the shuttle fleet is retired in 2010.