Henry Vanderbilt had a letter to Jerry Pournelle (go here and scroll way down):

Subject: Shuttle Foam correction

Jerry,

Seems my good deed for the day is to serve as an example of why one shouldn't fulminate on the basis of one info source. After firing off yesterday's screed about how easy it'd be to fix the Shuttle External Tank's foam- shedding problems, I checked around some, and discovered that "it's all the EPA's fault!" is more urban legend than fact. Alas, an ET fix isn't that simple.

To be brief, the Shuttle ET has had problems with shed foam damaging the orbiter thermal protection surfaces from the very start. The problem goes back to the design days, when the Orbiter designers didn't tell the Tank designers that oops, the TPS was going to be too fragile to handle ice falling off the tank at launch, until after the External Tank design was set. The foam was a last-second patch, and has never worked right; there have been shed-foam hits on the TPS every flight the Shuttle has ever made. More on some, less on others, as production quality and methods have varied and the ET engineers have tried a series of fixes. (There's a good account of all this at this site

The killer to the "EPA dunnit!" story is in this excerpt from the Columbia accident report: "The change in blowing agent affected only mechanically applied foam. Foam that is hand sprayed, such as on the bipod ramp, is still applied using CFC-11." IE, they were still using the original composition foam on the ramp area that broke loose and killed Columbia, and on the ramp area where a big piece broke loose on Discovery's launch the other day.

Now, my friend the adhesives engineer's comment is still apropos; bad technique in hand application can cause airpockets and/or bad adhesion between layers, either or both of which can help chunks break loose. QC at the ET plant in Michoud is definitely one of the things that needs looking at here.

My comment on NASA's organizational culture stands too; it is abundantly clear now there was considerable wishful thinking involved in declaring the problem solved after two and one- half years and several billion dollars spent. NASA's internal management culture is far from fixed.

But in passing on the EPA-dunnit net legend, oops, I goofed.

Henry Vanderbilt

All I know is that a billion dollars is a lot of money. You can buy a whole new program with new ships for a lot less. But to NASA it's chicken feed, and they aren't even ashamed that after a billion they can't keep the foam from flaking off to hit vulnerable spots.