BRIAN CARNELL REPORTS that the spray-on foam insulation used on the Shuttle external tank was reformulated to be CFC-free — and that one of the side effects is an increase in flaking. He has more on the subject — including a report that the reformulated foam led to flaking that caused significant damage to tiles on an earlier Shuttle mission — here. Very interesting. This New York Times story mentions the foam problem, but not the reformulation.