'urban myth' of environmentalist cause of foam loss

On Sat, 30 Jul 2005 08:38:08 GMT, Christopher P. Winter
wrote:

On Sat, 30 Jul 2005 02:13:50 GMT, "Jim Oberg"
wrote:

Anybody seen any good sites that discuss and refute
the widespread urban legend that the shuttle foam loss
was the fault of environmental regulations that outlawed
freon in the foam application? Ditto the old story that
outlawing asbestos led to the failure of the O-ring on
Challenger?

Thanks!

Jim O


This might be worth a look.

http://www.msfc.nasa.gov/FOIA/docs/goldberg%20memo.pdf


That is, it might be if the URL were still valid. It comes from a 2003
thread here in sci.space.

I didn't get anywhere searching NASA for "goldberg memo". But try these
URLs:

http://www.nasa.gov/pdf/45327main_hcfc2_001.pdf
http://www.nasa.gov/pdf/45328main_hcfc3_001.pdf
http://www.nasa.gov/pdf/45329main_hcfc4_001.pdf
http://www.nasa.gov/pdf/45330main_hcfc5_001.pdf
http://www.nasa.gov/pdf/45331main_hcfc5_002.pdf


http://www.nasa.gov/pdf/111156main_R...th_changes.pdf (738KB)

http://techreports.larc.nasa.gov/ltr...4-tm213256.pdf
(1916KB)
Assessment of Technologies for the Space Shuttle External Tank Thermal
Protection System and Recommendations for Technology Improvement
/Part 2. Structural Analysis Technologies and Modeling Practices/

I couldn't find a Part 1.

http://www.nasa.gov/pdf/112315main_RTF_changes_pk.pdf (4808KB)

On 2005-07-30, David Lesher wrote:

So... chicken wire. Over the foam, install space-rated chicken wire.
The idea being not that it will stop the foam shedding, but any part
that does come loose will be chopped up into 1" squares as it departs.

Alternately, any part that comes loose tears a chunk of chickenwire away
with it... and even without that, you go from having one block that may
or may not hit to lots of small bits almost guaranteed to shotgun the
belly. Probably not helping much.

Also, hmm. You're looking at an additional thousand pounds or two in the
weight of the mesh, says the back of this envelope - which is a sizeable
fraction of the amount saved by introducing the lighter ET in the first
place, and pretty much comes directly out of the payload allocation.

--
-Andrew Gray

Andrew Gray writes:

So... chicken wire. Over the foam, install space-rated chicken wire.
The idea being not that it will stop the foam shedding, but any part
that does come loose will be chopped up into 1" squares as it departs.

Alternately, any part that comes loose tears a chunk of chickenwire away
with it... and even without that, you go from having one block that may
or may not hit to lots of small bits almost guaranteed to shotgun the
belly. Probably not helping much.

The joke's on me. I was not serious; but a reporter friend on the
shuttle beat [now finally able to see his wife+kids after weeks @
KSC-Houston-KSC-EDW...] reports that one proposal is for some
kind of ?nylon/kevlar? mesh...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Andrew Gray wrote:

Also, hmm. You're looking at an additional thousand pounds or two in the
weight of the mesh, says the back of this envelope - which is a sizeable
fraction of the amount saved by introducing the lighter ET in the first
place, and pretty much comes directly out of the payload allocation.

Carbon fiber or Kevlar 'chicken wire' shouldn't be nearly that much. If
I've done my math right, the surface area of the ET is about 1281 m^2.
Fairly thick Kevlar cloth weighs about 200 grams/m^2. That gives you a
total of about 256 kg extra mass for wrapping the whole thing in one
layer of cloth. Not trivial, but not entirely insane.

If, rather than using cloth, you used a mesh with thicker fibers in a
1cm grid or so, it should mass quite a bit less, while preventing any
big chunks from falling off in one piece. Of course, the devil is in
the details. The obvious problem is how do you keep the mesh in place.
Does embedding mesh in the foam a make it stronger, or does it cause a
stress point that makes the outer layers shed even more ? Putting it on
the outside might initially keep foam debris to a minimal size (even if
a big chunk comes loose, it gets strained through a 1cm mesh) but once
a certain amount comes out, your mesh will be flapping in the breeze. A
mesh on the outside would then also have to stand up to aero and rocket
exhaust heat. Then there's the issues of thermal expansion/contraction
(ISTR the inside of the ET shrinks about 6 inches)

The tank folks must have looked at re-enforcement and external skins.
The fact that they haven't gone for something like that tells me it
isn't an easy solution.