This week's problem with space shuttle Discovery—insulating foam flaking off— is the same problem that contributed to the demise of Columbia two years ago. Why, after a quarter-century of shuttle use, are we just now having problems with this?
In truth, the Columbia disaster was six years in the making, and this week's Discovery problems were pretty much inevitable. In 1997, bowing to environmentalist nags, NASA replaced the shuttles' Freon-based insulating foam with a more eco-friendly foam. The problem with the newer foam is that it is less impact resistant (Steven Milloy notes that problems with damaged tiles increased significantly once the new foam was introduced) and is more prone to brittleness (which explains the flaking).
Even though NASA was specifically exempted from the CFC phaseout in 2001, they continued to use the less-effective foam. Not even the Columbia disaster persuaded them to switch back. Now we have a grounded shuttle fleet as NASA pretends, in the grand tradition of O.J. Simpson, to search for The Real Culprit.