Space Forum / Shuttle / September 2003

From stmx3:

?

(If NASA can recognize the safety threat, I'd like to think that this
forum can see validity in that as well.)

I've been repeatedly pointing out that the foam problem *was* caught.
THIS is my best guess as to why all panel members "resigned".
Reporters have plenty of information available to them to press key
officials as to why the known problem was neglected.  Consider the
info in this one webpage:

http://quest.arc.nasa.gov/people/journals/space/katnik/sts87-12-23.html

Excerpt:
------
STS-87 is Home! The Post-Flight Inspection Begins
by Greg Katnik
December 23, l997

STS-87 rolled to a stop...the extent of damage at the conclusion of
this mission was not "normal." ... During the STS-87 mission, there
was a
change made on the external tank. ... Foam cause damage to a ceramic
tile?! That seems unlikely, however when that foam is combined with a
flight velocity between speeds of MACH two to MACH four, it becomes a
projectile with incredible damage potential. The big question? At what
phase of the flight did it happen and what changes need to be made to
correct this for future missions?  ...  It was determined that during
the
ascent, the foam separation from the external tank was carried by the
aerodynamic flow and pelted the nose of the orbiter and cascaded aft
from
that point. Once again, this foam was carried in a relative air-stream
between MACH two and MACH 4!   ...  As this investigation continues, I
am very comfortable that the questions will be answered and the
solutions applied.
------

There are lots more people directly involved who could answer
questions to give an accounting for horrible mistakes that were made.

~ CT

Full article:
----------------------
FIELD JOURNAL

STS-87 is Home! The Post-Flight Inspection Begins

by Greg Katnik
December 23, l997

STS-87 rolled to a stop; the mission was complete! That statement
would
be true for the flight of the Columbia, however a new mission began
when the wheels of the Columbia came to a stop -- the post flight
inspections. My division is responsible for the overall analysis of
these
inspections and we insure that all changes made, due to these
inspections,
do not affect other areas that may jeopardize the flight-worthiness of
the shuttle. This division does not focus on one specific area, but
analyzes all information and ensures that all aspects are kept in
balance.

Immediately after the Columbia rolled to a stop, the inspection crews
began the process of the post flight inspection. As soon as the
orbiter
was approached, light spots in the tiles were observed indicating that
there had been significant damage to the tiles. The tiles do a
fantastic job of repelling heat, however they are very fragile and
susceptible
to impact damage. Damage numbering up to forty tiles is considered
normal on each mission due to ice dropping off of the external tank
(ET)
and plume re-circulation causing this debris to impact with the tiles.
But the extent of damage at the conclusion of this mission was not
"normal."

The pattern of hits did not follow aerodynamic expectations, and the
number, size and severity of hits were abnormal. Three hundred and
eight
hits were counted during the inspection, one-hundred and thirty two
(132) were greater than one inch. Some of the hits measured fifteen
(15)
inches long with depths measuring up to one and one-half (1 1/2)
inches.
Considering that the depth of the tile is two (2) inches, a 75%
penetration depth had been reached. Over one hundred (100) tiles have
been
removed from the Columbia because they were irreparable. The
inspection
revealed the damage, now the "detective process" began.

During the STS-87 mission, there was a change made on the external
tank. Because of NASA's goal to use environmentally friendly products,
a
new method of "foaming" the external tank had been used for this
mission
and the STS-86 mission. It is suspected that large amounts of foam
separated from the external tank and impacted the orbiter. This caused
significant damage to the protective tiles of the orbiter. Foam cause
damage to a ceramic tile?! That seems unlikely, however when that foam
is
combined with a flight velocity between speeds of MACH two to MACH
four,
it becomes a projectile with incredible damage potential. The big
question? At what phase of the flight did it happen and what changes
need to
be made to correct this for future missions? I will explain the entire
process.

The questions that needed to be answered were:

* what happened?

* what phase of flight did it happen in?

* why did it happen?

* what corrective action is required?

At this point, virtually every inch of the orbiter was inspected and
all hits were documented and mapped to aid in visualizing the damage.
Maps were constructed of the lower surface, the left and right
surfaces
and the top surface of the orbiter. At this point, a "fault tree" was
created. The fault tree provides a systematic approach in considering
all
possibilities of what may have happened. Everything that is on the
fault tree is considered to be legitimate until it is totally ruled
out.
Some of the considerations were where the damage occurred -- in the
OPF,
in the VAB, or on the pad before launch. These were quickly eliminated
because an inspection at T-3 ("t minus three") hours takes place on
each mission and everything was normal.

After these and many other considerations were eliminated, the focus
was placed on the ascent, orbit and re-entry phase of the mission.
Because of the fore and aft flow characteristics of the damage sites,
and the
angle of penetration, the ascent phase seemed most likely. The orbit
phase of flight was eliminated because the characteristics of these
types
of hits (most likely meteorites or space debris) occur in a random
pattern and direction. Re-entry was eliminated because the "glazing
and
re-glassifying" of the tiles due to heat upon re-entry (a normal
process)
indicated that the damage had occurred prior to this phase. The
fault-tree was now pointing to the ascent phase.

The pictures that were taken by cameras mounted in the orbiter
umbilical began to give the first clues. These cameras are designed to
turn on
during the solid rocket booster (SRB) separation, and turn off after
the separation is complete, thereby recording the event. This process
occurs once again when the external tank separates from the orbiter.
The
initial review of these photographs did not reveal any obvious damage
to
the external tank. No foam missing, no "divots" (holes) and no
material
loss. Everything appeared normal.

The SRBs were then focused on for the answers. After inspection of the
SRBs, no clues were found. In fact, the solid rocket boosters looked
to
be in great condition. Where to now? The external tank photographs
were
magnified and reviewed once again. This time some material loss was
noted, but not in a significant degree. The attention was now focused
on
the crew cabin cameras. These cameras gave more of a side view of the
external tank as it tumbled back to Earth. These photographs revealed
massive material loss on a side of the external tank that could not be
viewed by the umbilical cameras!

Where are we now? One of the questions had now been answered. The
ascent phase of flight was when the damage occurred. With the
information
provided by the photography and the mapped flow of damage, a logical
reason could be established as to "what" happened. It was determined
that
during the ascent, the foam separation from the external tank was
carried by the aerodynamic flow and pelted the nose of the orbiter and
cascaded aft from that point. Once again, this foam was carried in a
relative
air-stream between MACH two and MACH 4!

Now the big question -- why? The evidence of this conclusion has now
been forwarded to Marshall Space Flight Center (MSFC) because this is
the
design center for the external tank. MSFC will pursue the cause of
damage. Here are some descriptions of some of the considerations:

* The primer that bonds the tank foam to the metal sub-stream was
defective and did not set properly. This was eliminated as a cause
because
the photography indicated that the areas of foam loss (divots) did not
protrude all the way down to the primer.

* The aerodynamics of the roll to "heads up." The STS-87 mission was
the first time this maneuver had ever been completed.

* The STS-86 mission revealed a similar damage pattern but to a much
lesser degree than STS-87. The STS-86 tile damage was accepted ruled
as
an unexplained anomaly because it was a night launch and did not
provide
the opportunity for the photographic evidence the STS-87 mission did.
A
review of the records of the STS-86 records revealed that a change to
the type of foam was used on the external tank. This event is
significant because the pattern of damage on this flight was similar
to STS-87
but to a much lesser degree. The reason for the change in the type of
foam is due to the desire of NASA to use "environmentally friendly"
materials in the space program. Freon was used in the production of
the
previous foam. This method was eliminated in favor of foam that did
not
require freon for its production. MSFC is investigating the
consideration
that some characteristics of the new foam may not be known for the
ascent environment.

* Another consideration is cryogenic loading, specifically hydrogen
(-423 degrees Fahrenheit) and oxygen (-297 degrees Fahrenheit). These
extreme temperatures cause the external tank to shrink up to six (6)
linear
inches while it is on the pad prior to launch. Even though this may
not
seem much when compared to the circumference of the external tank, six
inches of shrinkage is significant.

This is where the investigation stands at this point in time. As you
can imagine, this investigative process has required many hours and
the
skills of many men and women dedicated to the safety of the shuttle
program. The key point I want to emphasize is the process of
investigation,
which is coordinated amongst many people and considers all
possibilities. This investigation has used photography, telemetry,
radar coverage
during the launch, aerodynamic modeling, laboratory analysis and many
more technical areas of expertise.

As this investigation continues, I am very comfortable that the
questions will be answered and the solutions applied. In fact, some of
the
solutions are already in progress. At present the foam on the sides of
the
tank is being sanded down to the nominal minimum thickness. This
removes the outer surface, which is tougher than the foam core, and
lessens
the amount of foam that can separate and hit the orbiter.

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