s.s.p. big branes, a call for a refresher course

The EPA-foam issue has cropped up again on talk radio. (sigh) Let me
know if I'm close to the following facts here.

0) At some time in the 1990s EPA policy called for the end of the use of
freon in processes that affected the ET foam insulation.

1) There was a period in the mid-late 1990s when ET insulation was
applied with a mix of old and new methods. Old school foam used in what
were deemed most critical areas and the new freon-free foam in other areas.

2) Later analysis showed that both areas continued to suffer from foam
loss. (What kind, and how much?)

Columbia's ET was old or new type?

Thank you. I'm trying to educate myself here. Researching this topic has
been a mess on google. I've gotten people blaming/crediting the EPA
going all the way back to Challenger O-ring putty. I've even gotten a
WTF??!! whiff of an EPA-FDA-EPHEDRA-FREON DIABOLICAL CONSPIRACY!!! AIEEEE!


--
It Came From C. L. Smith's Unclaimed Mysteries.
http://www.unclaimedmysteries.net

Of course I went to law school. - Warren Zevon, "Mr. Bad Example"

Unclaimed Mysteries
theletter_k_andthenumeral_4_doh@unclaimedmysterie s.net wrote in
link.net:

The EPA-foam issue has cropped up again on talk radio. (sigh) Let me
know if I'm close to the following facts here.

0) At some time in the 1990s EPA policy called for the end of the use
of freon in processes that affected the ET foam insulation.

1) There was a period in the mid-late 1990s when ET insulation was
applied with a mix of old and new methods. Old school foam used in
what were deemed most critical areas and the new freon-free foam in
other areas.

2) Later analysis showed that both areas continued to suffer from foam
loss. (What kind, and how much?)

Columbia's ET was old or new type?

Thank you. I'm trying to educate myself here. Researching this topic
has been a mess on google. I've gotten people blaming/crediting the
EPA going all the way back to Challenger O-ring putty. I've even
gotten a WTF??!! whiff of an EPA-FDA-EPHEDRA-FREON DIABOLICAL
CONSPIRACY!!! AIEEEE!

From the report of the Columbia Accident Investigation Board, Volume 1, p.
129:

"The foam loss problem on STS-87 was described as "popcorning" because of
the numerous popcorn-size foam particles that came off the thrust panels.
Popcorning has always occurred, but it began earlier than usual in the
launch of STS-87. The cause of the earlier-than-normal popcorning (but not
the fundamental cause of popcorning) was traced back to a change in foam-
blowing agents that caused pressure buildups and stress concentrations
within the foam. In an effort to reduce its use of chlorofluorocarbons
(CFCs), NASA had switched from a CFC-11 (chlorofluorocarbon) blowing agent
to an HCFC-141b blowing agent beginning with External Tank-85, which was
assigned to STS-84. (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.)"


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

the trapped gas (what makes CPR-488 what it is/was) in the foam (that
forms most of the space in the et foam matrix and the reason for its
extreme light weight) is the reason for "popcorning". Research done on
the effects to ET foam by vacuum and high UV in 1988-1989 should the it
will brake down nearly 100% in 48-72 hours resulting in very large
debris filed around the tank if one was ever left on orbit. It also
outgases about 20% of its total mass in 12 hours (about 16% more than
what's allowed in or near the shuttle payload bay). The original ET
foam was qualified for 8.5 min (from T-0) and that's all. The changes
demanded by the EPA in the 90's did have a bad impact. CPR-488 is
without a doubt the best insulation ever developed by man and a star
performer on the STS program.

Cheers!