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

Unclaimed Mysteries
<theletter_k_andthenumeral_4_doh@xxxxxxxxxxxxxxxxxxxxxx> wrote in
news:BF8Ge.18484$aY6.8352@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx:

> 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

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Relevant Pages

  • Re: Diagram of Orbiter Hits
    ... Many non-station flights continued to use the lightweight tank. ... The rate of hits increased when the foam blowing agent was changed from CFC ... bipod ramps and the PAL ramp, continued to use CFC as the blowing agent. ...
    (sci.space.shuttle)
  • Re: A foam question for the experts here.
    ... > As of Columbia's last flight, ramp foam of the type that failed still ... > used CFCs as a blowing agent. ... Acreage foam switched to a more ...
    (sci.space.shuttle)
  • Re: A foam question for the experts here.
    ... As of Columbia's last flight, ramp foam of the type that failed still ... used CFCs as a blowing agent. ...
    (sci.space.shuttle)