This just came in from Fox News. Dow foam experts... is it possible that "PC foam" was the root cause"? All that follows below this line came from Fox News just like you see it here.
A chunk of foam insulation broke off the external fuel tank during launch, perhaps damaging Columbia�s heat-protecting tiles. �We�re making the assumption that the external tank was the root cause of the accident,� said shuttle program manager Ron Dittemore in the immediate aftermath.
It seemed a very reasonable assumption based on Columbia�s history.
Until 1997, Columbia�s external fuel tanks were insulated with a Freon-based foam. Freon is a chlorofluorocarbon (CFC) supposedly linked with ozone depletion and phased out of widespread use under the international treaty known as the Montreal Protocol.
Despite that the Freon-based foam worked well and that an exemption from the CFC phase-out could have been obtained, NASA succumbed to political correctness. The agency substituted an allegedly more eco-friendly foam for the Freon-based foam.
PC-foam was an immediate problem.
The first mission with PC-foam resulted in 11 times more damaged thermal tiles on Columbia than the previous mission with the Freon-based foam.
A Dec. 23, 1997, diary entry on the NASA Web site reported: �308 hits were counted during the inspection, 132 were greater than 1-inch. Some of the hits measured 15 inches long, with depths measuring up to 1.5 inches. Considering that the depth of a tile is 2 inches, a 75 percent penetration depth had been reached.�
More than 100 tiles were damaged beyond repair, well over the normal count of 40. Flaking PC-foam was the chief suspect.
In 2001, the Environmental Protection Agency exempted NASA from the CFC phase-out. Even assuming for the sake of argument that widespread use of CFCs might significantly damage the ozone layer, the relatively small amount used by NASA would have no measurable impact. The bulk of CFC use, after all, was in consumer products such as air conditioners, refrigerators and aerosol cans.
But contrary to the exercise of common sense, NASA didn�t return to the safer Freon-based foam. Instead, NASA knowingly continued to risk tile damage -- and disaster -- with reformulated PC-foam.
This is obviously a potentially embarrassing situation for NASA.
In what smacks of an effort to avoid blame, NASA is now claiming the disintegration of Columbia has turned into a scientific mystery.
NASA says computer modeling fails to show how foam insulation striking the thermal tiles could do enough damage to cause catastrophe -- apparently ignoring that flaking foam substantially penetrated thermal tiles on an earlier flight.
NASA has even offered up the ultimate exculpatory theory -- that space junk or even a meteor could have hit the wing and damage the thermal tiles.
On the technical side:
Does anyone on the board know if Freon blowning agent was replaced with with carbon dioxide? Just curious.
I recall CO2 being a reasonable plasticizer, from a mechanical properties point of view. So, if the newer foam is alittle less rubbery and alittle more glassy, perhaps its durometer numbers are higher, meaning it's harder. Maybe when it strikes the tiles, the foam has less give, thereby delivering more damage.
Also, is this a styrenic foam, or is it a polyurethane?
I am assuming that PC used here means "politically correct," not polycarbonate. If it was carbonate, them tiles would be history; it's tough stuff. (Also, I've never heard of foaming polycarbonate, although I guess it seems possible. Anyone know?)
The tanks are sprayed with Poly Urethane foam. Freon R11 & R 12 were the primary Blowing Agents before the Montreal Protocol. Today there are replacement materials that have less ODP (ozone depletion potential) the physical properties of the materials did not change much once the foams were reformulated with the new Blowing Agents. I doubt that they are using CO2 technology on the tanks. This technology does exist for PU but not commercial for spray foams. It is hard for me to imagine that the foam could knock a tile off.
Hope this helps
I'm sure that the author meant "politically correct" when he said "PC".
I've sent the author an e-mail to ask whether he has talked to a foam expert about this.
If you want to know more about the author, go to www.junkscience.com There are some interesting articles there listed in sequence by days. That is, articles published Feb. 7, Feb. 6, Feb. 5 etc.
There's also a brief reference to "maybe changing the foam did it" in the N. Y. Times.
If you are so inclined, you may want to do some futher digging. Earlier reports (last Monday) indicated that this was an older tank. I think I read it was manufactured and coated in 1999.
This older tank was heavier than the tanks currently in use, but was of acceptable weight for the Columbia's lower orbit and payload on this flight. Columbia was not able to reach Space Station altitudes with the payloads needed for ISS work and so it had been relegated to lower earth orbit missions.
When I read this, I had to ask myself "would age of the foam be a factor?" Your thoughts?
By the way, everyone wants to know what happened, particularly down here around JSC with the debris area just up highway 59. I don't agree with Fox being critical of NASA, particularly claiming coverup with words like "scientific mystery..."
NASA has been amazingly open with the data and their various thought processes as they go through the investigation - still less than a week old. Try to catch some of Ron Dittemore's unedited briefings on C-SPAN. Amazing. I've never seen a more able technical spokesman.
I don't see any attempt to redirect thoughts one way or the other. They seem to be trying to investigate all possibilities and not jump to a false conclusion. As you well know the "apparently obvious" can be a big mental stumbling block in an investigation. Fox, of course, never has a problem racing to a conclusion.
When has any chemical company been as open with a root cause investigation?