Failure at PAL Ramp Removal?

But this pivot myth I still saw a few years ago in a TV documentary
again. To get the effect it looked like a pivot angle of 10 degree or
more was necessary. The SRB had to pivot such an angle against the high
air pressure (it was just seconds after max-q). And it had to pivot back
within a second as it came out of the ET cloud on straight course.


Actually it went through the burning cloud of LOX and LH2 and came out
on the opposite side it started from, as the close-up photos of the
vehicle break-up show:
http://www.aerospaceweb.org/question...ns/q0122.shtml
....in fact, the pivot angle is very severe on the damaged SRB, as these
photos from that page show:
http://www.aerospaceweb.org/question.../challenger7.j
pg

Once
imagined the timing and the forces/masses involved one need no back
of the envelope calc to dismiss it. It was such a rediculous scenario
that I considered it in 1986 as usual journalist fast written trash.
It was annoying to hear it from the Rogers report and much later
documentaries.



The photos don't lie- it's very easy to see which SRB is damaged, and
how it ends up on the opposite side of the break-up event* from where it
started at, due to pivoting inwards as it detached.

Ok, you convinced me that the SRBs changed side and pivoted to a much
higher angle than 10 deg, but _after_ break-up. This has nothing to do
with the ET failure itself. The nose of the right SRB could not pivot
inside the ET to cause it to fail. The telemetric data - as reviewd by
the House report - ruled it out.

Besides I rememmber a wide angle shoot of the ET cloud and the SRB trails
just about 5 seconds after break-up, before wind changed it. I could
not find the pic on the net now. Both SRBs trails came out of the cloud
with about the same outward deviation before they got paralell again.
For "the right SRB did it" one would expect a straight trail of the left
SRB. But it indicated both SRB pivoted about the same angle inward.

I think the extreme pivoting happend after the "SRB-beam" in the intertank
area brocke. Before it brocke it bended upward or downward. By that, both
SRB were violently pulled inward and pivoted (up to 40 degree?). This
was after the ET already failed.

The initial question was how did the ET fail? It has some relevance for
the coming Discovery mission if the repress line is in danger (lets hope
it will not) because of the removed PAL ramp. For the Challenger ET I see
the following scenarios still open:

#1 Pressure loss (Pessin`s 2002 paper)
#2 Break up of internal load structure, mainly intertank SRB-beam
#3 LH2 tank propelled upwards as aft dome sperated

#1 I only read last year. Cant remember it from the Rogers or the House
report. Pessin as senior managment/engineer should be in the position to
know, I thought. But today I found:

Figure 66. Liquid Hydrogen Ullage Pressure and Tank Pressure Anomalies:
http://history.nasa.gov/rogersrep/v3n47b.htm

and Figure 72. Sharp MPS Liquid Oxygen Inlet Pressure Drop:
http://history.nasa.gov/rogersrep/v3n50b.htm

Now I`m surprised that the LH2 pressure shows no sudden pressure drop
(like expected for #3) and was up to operation level till the last reading.
How does it fit to Pessins claim of pressure loss? I dont know for the
moment. The sudden pressure loss in the LOX tank points to an LOX aft
dome damage. Either by #2 or #3. In this interesting image

http://images.jsc.nasa.gov/luceneweb...STS5 1L-10167
we see a faint shock-cone-like originating from the intertank. I think it
may be LOX venting through the air-holes in the intertank. Then it would
slightly favour #2 over #3. Because a SRB-beam break by #3 I would expect
some more evidence to it.

At the website you mentioned, the upper part image of "Failure of the
liquid oxygen tank in the ET" is interesting. I think it shows an
asymetrical collapse of the LOX tank to the right side were the inner
SRB-beam was overloaded. It would fit #2 and the wreck evidence mentioned
by Henry.


* No, I'm not going to call it an "explosion"- we don't need to start
_that_ all over again. :-)

Right Pat, lets save it for Apollo 13


Pat


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