Foam Failure Causes?

The three foam shedding events visible on the
ET cam video all occurred well after SRB
separation, when the vehicle was more than
30 miles high. It seems to me that in each case
the foam "popped" off of the tank rather than
"tearing" off. This failure mode seems to me to
be more likely due to thermal or trapped gas
effects rather than aerodynamic forces, which
I believe were exactly the modes that NASA/
Lockheed were working to prevent.

The good news is that the foam held up during the
worst aero-load portions of the ascent. But the
bipod area failure, especially, is worrisome
because this area was modeled and redesigned and
carefully manufactured and examined and reexamined
but still failed. I'm not sure how NASA proceeds
on the foam issue from this point.

Lockheed's Centaur has flown a few times with a
white coating over the LH2 tank insulation, usually
when the tank is housed inside the Atlas 5-5xx big
fairing. Could this method offer a solution to the
shuttle foam shedding problem?

- Ed Kyle

"Ed Kyle" wrote in news:1122699587.870748.267060
@f14g2000cwb.googlegroups.com:

The three foam shedding events visible on the
ET cam video all occurred well after SRB
separation, when the vehicle was more than
30 miles high. It seems to me that in each case
the foam "popped" off of the tank rather than
"tearing" off. This failure mode seems to me to
be more likely due to thermal or trapped gas
effects rather than aerodynamic forces, which
I believe were exactly the modes that NASA/
Lockheed were working to prevent.


One thing we've learned is to totally avoid using insulating foam in
built-up "structural" components of the tank. The bipod ramp and the PAL
ramp are examples of this approach -- pretending that the ascent
environment is sufficiently benign that thick foam structures can
withstand the aerodynamic & structural stresses.

It pretty clearly isn't...

--
I was punching a text message into my | Reed Snellenberger
phone yesterday and thought, "they need | GPG KeyID: 5A978843
to make a phone that you can just talk | rsnellenberger
into." Major Thomb | -at-houston.rr.com

Reed Snellenberger wrote:

One thing we've learned is to totally avoid using insulating foam in
built-up "structural" components of the tank. The bipod ramp and the PAL
ramp are examples of this approach -- pretending that the ascent
environment is sufficiently benign that thick foam structures can
withstand the aerodynamic & structural stresses.


I remember back when they designed the Shuttle they had a very hard time
modeling the second-by-second airflow and shockwave interactions between
the ET, Orbiter, and SRBs during ascent accurately despite using the
fastest computers of the time.

Pat

On 29 Jul 2005 21:59:47 -0700, "Ed Kyle" wrote:

The three foam shedding events visible on the
ET cam video all occurred well after SRB
separation, when the vehicle was more than
30 miles high. It seems to me that in each case
the foam "popped" off of the tank rather than
"tearing" off. This failure mode seems to me to
be more likely due to thermal or trapped gas
effects rather than aerodynamic forces, which
I believe were exactly the modes that NASA/
Lockheed were working to prevent.

At this height it seems like a minor problem.

The good news is that the foam held up during the
worst aero-load portions of the ascent.

Kind of interesting how NASA has been all doom and gloom and full of
self blame. Passed through all that lower atmosphere with no loss at
all. That is the Columbia problem fixed.

But the
bipod area failure, especially, is worrisome
because this area was modeled and redesigned and
carefully manufactured and examined and reexamined
but still failed. I'm not sure how NASA proceeds
on the foam issue from this point.

I have been looking closely at this. I do strongly believe that this
foam loss is directly to do with the SRB separation. So NASA running
around fearful over what could happen if this happened earlier into
this trip seems very misplaced.

This foam could have been lost due to thermal issues, vibrations, but
I did also consider pressure. What I find interesting is that this
foam directly follows the path of the SRB that separated only a couple
of seconds previously.

That seems logical. This being the case means that this foam could
never have hit Discovery anyway, when it was being sucked in the other
direction.

Anyway, I expect that the people at NASA can estimate what caused this
better than what I can. Seems that NASA, well on their path of
self-doubt, is currently blaming inadequate pre-launch testing.

Cardman.

Cardman wrote:

Kind of interesting how NASA has been all doom and gloom and full of
self blame. Passed through all that lower atmosphere with no loss at
all. That is the Columbia problem fixed.

They planned and expected to fix all significant foam shedding, and
clearly didn't. This shows they didn't fully understand the problem,
which is obviously a cause for serious concern.

It isn't a given the Columbia problem is fixed. They need to determine
if they just got lucky that the shedding being at high altitude on this
flight, or if there was something specific about that environment which
caused it. All kinds of curves can fit a one sample data set.

Even if they determined that it could only happen around SRB sep, their
current flight rules don't allow that much foam loss in any part of
flight. Further analysis might show loss above a certain altitude is
safe, but its not a given.

I have been looking closely at this. I do strongly believe that this
foam loss is directly to do with the SRB separation.
Based on what ? Sure, it is a fair guess, but until the actual analysis
is done, it's just a guess. This kind of a guesstimate is a big part of
what doomed both Columbia and Challenger.
So NASA running
around fearful over what could happen if this happened earlier into
this trip seems very misplaced.

I don't see this at all. It has largely been the media that has been
spreading the FUD. NASA has learned that their understanding of the
foam was incomplete, and know they need to fix that before they fly
again. The exact outcome will depend on a lot of hard work involving
data that isn't available to most of us on this NG.

On 1 Aug 2005 14:38:21 -0700, "hop" wrote:

Cardman wrote:

Kind of interesting how NASA has been all doom and gloom and full of
self blame. Passed through all that lower atmosphere with no loss at
all. That is the Columbia problem fixed.

They planned and expected to fix all significant foam shedding, and
clearly didn't. This shows they didn't fully understand the problem,
which is obviously a cause for serious concern.

Maybe their belief simply exceeded reality. It seems quite an
interesting notion to stick foam to a thin piece of metal that
vibrates like water during this trip.

It isn't a given the Columbia problem is fixed. They need to determine
if they just got lucky that the shedding being at high altitude on this
flight, or if there was something specific about that environment which
caused it. All kinds of curves can fit a one sample data set.

Well my advice would be that you cannot do sampling on one. So they
simply cannot ever tell that until they launch again.

Even if they determined that it could only happen around SRB sep, their
current flight rules don't allow that much foam loss in any part of
flight. Further analysis might show loss above a certain altitude is
safe, but its not a given.

Following Columbia this is not unexpected. That does not mean that the
risk is not negligible either.

I have been looking closely at this. I do strongly believe that this
foam loss is directly to do with the SRB separation.

Based on what ? Sure, it is a fair guess, but until the actual analysis
is done, it's just a guess. This kind of a guesstimate is a big part of
what doomed both Columbia and Challenger.

And they can do all the analysis all they want. The simply fact is
that the SRB separated and shortly following this foam came off. These
two events seem very much related.

Only further launches will highlight if this happens again.

Since I expect NASA's analysis to reach no other conclusion, then they
will simply patch up that section to stop it doing it again. Maybe one
reason why they don't understand this foam loss is simply because this
is the first real data return.

So NASA running
around fearful over what could happen if this happened earlier into
this trip seems very misplaced.

I don't see this at all. It has largely been the media that has been
spreading the FUD. NASA has learned that their understanding of the
foam was incomplete, and know they need to fix that before they fly
again.

Even if oddly enough only flying again can close those holes in their
knowledge. Still, this launch provided a lot of data, where this may
tell them what they need.

The exact outcome will depend on a lot of hard work involving
data that isn't available to most of us on this NG.

Yes, well. NASA should keep in mind that their ISS is not being built
and Hubble is not being serviced all the time that they concern
themselves over this minor matter.

Should you own a scanner, then it is worth checking out the
frequencies used by commercial aircraft. What is interesting is that
you can hear pilots discussing all kinds of aircraft faults, including
engine failure. And for anything much too spicy for public knowledge
they switch to a secure channel.

My point being is that they patch up their planes. Fix the faults and
failures. Give it a quick strong test to see if it works, then to
launch back into the sky only an hour or two later.

Most travelers would not wish to know that their aircraft was
seriously malfunctioning not too long ago. And well the history of air
travel proves that this system works to both do the job and to keep
everyone alive.

NASA likes to make a mountain out of a mole hill. And sure enough
whatever they do this killer shuttle is bound to one day catch them
out in other ways. We can hope not of course.

Anyway, I hope that they keep in mind that their human spaceflight
section is not currently doing much human spaceflight. I seem to
recall the time when they did 17 shuttle launches in one year. Then
Challenger blew and things have gone downhill ever since.

Cardman.