Remember the question why NASA did not release their results on the
in orbit repair options for Columbia?

Incorrect. The results were released with the CAIB report, both as a
chapter in the main report and as an appendix.

The only "results" they released was a statement that their tests were
inconclusive. No report what they tested, how they tested neither
the results they got.

They did no materials testing, only analysis, and very limited analysis
at that. They didn't just say the analysis was inconclusive. They said
more than that.

"The assessment of the level of difficulty of the repair operation
is high. The level of risk to the crew is moderate and the risk of doing
additional damage to the Orbiter is high (i.e. enlarging the wing leading
edge breach). The overall assessment of the expectation of task success
is moderate to low, depending on damage site characteristics and the
required repair technique."

"The results while inconclusive, do not indicate this option was likely
to succeed."

Actually, what you cite above is a report by a NASA team. It was
published by the CAIB but the CAIB was not involved in its writing.
The CAIB conclusion on the subject did not oppose it because they had
no other data then the NASA report to base on:

"Because the NASA team could not verify that the repairs would survive
even a modified re-entry, the rescue option had a considerably higher
chance of bringing Columbia's crew back alive." (CAIB Vol. 1)

In effect, the same guys who immediately after the diasater openly stated
"there was no way to repair" (they even said it that line as the astronauts
were still alive) did later the task to investigate whether their statement
was correct. They did it the NASA disaster way: "inconclusive"


It seems the results were too
unwanted obvious:

Gutierrez is wrong. And it turns out, so were NASA's results from the
CAIB report. The three years of work that have gone into RCC repair
capability since that report have made clear that the in-flight
repair options for Columbia would not have worked.

What is your source? Was it you who said something the same line over
a year ago claiming some knowledge of NASA tests not yet released? As
we got no source it was dismissed as one of the many Columbia Usenet
myths. But maybe there is a report out now. I`m not the only one eager
to read it!

It depends on what you mean by "report". NASA has published no report
directly addressing Columbia repair on STS-107. But then again, that's
not necessary. What I did was to read the CAIB report, both Volume 1
section 6.4 and Appendix D.13, and make careful note of the assumptions
both stated and implicit. Then I read on NASA's work on RCC repair and
entry aerothermodynamics since the CAIB report was published. This work
does not directly address 107, but the results of it invalidate the
assumptions from CAIB. It's as simple as that.

First, the results of the RCC impact tests at SwRI demonstrate that the
area around the hole in panel 8L almost certainly had surrounding areas
where the RCC was cracked and delaminated. Arcjet tests at Ames and JSC
demonstrate that RCC damage propagates rapidly along these cracks. So it
doesn't matter what the crew puts in the hole behind the panel to try to
stop the flow of superheated air; the damage will quickly spread and
allow the superheated air to simply go around the repair.

In simple words you assume the hole in the RCC would grow up until
most the RCC was consumed and the ice block was no longer a blockade.
That would be a clear "no way to repair". But I doubt that the
delamination would spread that fast. Its a plasma oxidation of an
otherwise covered RCC layer on the open crack surface. The hole may
be 2 cm wider after reentry, but not 4 times its size. As you read
it otherwise somewhere (or you got that impression there), please
give me your source.


Second, due to the improvised materials, the repair would not have been
smooth enough to prevent an early boundary layer transition. RCC is rated
to 3000 deg F, the lower surface black tiles to 2200 deg F. The shock
ahead of the vehicle contains superheated air at temperatures up to
10,000 deg F. It is the laminar (smooth) boundary layer that protects the
TPS from these extreme temperatures. Normally, the boundary layer trips
to turbulent well after the period of peak heating but rough surfaces can
result in early transitions. A transition prior to Mach 21 can cause
vehicle damage and a transition prior to Mach 24 can cause loss of
vehicle. The improvised Columbia repair would likely have gone turbulent
right from the beginning of entry (Mach 25), exposing the RCC panel and
the trailing black tiles to the superheated air. Columbia's damage
occurred at just about the worst possible location since the shock from
the nose cap intersects the shock from the leading edge between RCC
panels 5 and 13, depending on Mach number.

We had this issue here before, maybe not with you. Just summ:

1. the hole it had is a larger BL obstacle then any remaining
irregularities from an repair

2. there was no evidence of BL trip related damage by CAIB, it
all developed at the RCC

3. required smoothness criteria for the shuttle was to protect it
against any thermal damage to the tiles. This was to keep the tiles
reusable. In case of an emergency some tile damage would be accecptable.

4. on other missions Columbia had several early BL trips without serious
damage or without any damage at all.


--
JRF


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