From: Sam Milton (
Date: Fri Feb 07 2003 - 16:38:28 EST

  • Next message: Pinizzotto,Russell: "Root Cause Analysis"

    I know this will be off-topic, but this will only be one post.  I have been
    listening for a week now as theories are bandied about, and the media
    continues to try to play "gotcha" with scraps of technical information to
    try to prove somehow that some of the smartest engineers in the world were
    careless, or stupid, or lazy, or negligent in some way.  It really leaves a
    bad taste in my mouth.  As an chemical engineer myself (but not one of the
    smartest in the world), I can appreciate the complexities of the shuttle and
    all of the potential malfunctions.  It amazes me that these engineers like
    Mr. Dittemore maintain their cool with airhead reporters (Miles O'Brien
    excluded) asking questions about boundary-layer flow which they obviously
    were told to ask by some former something-or-other that their news
    organization has on the payroll.  They usually don't understand enough to
    ask the question.  Yes, the shuttle system has flaws, yes, it has design
    compromises, but it was a horse designed by a committee.  And it is all we
    have for at least seven years, probably, until the Orbital Space Plane
    enters service, assuming that happens.  Anyway, now I feel better.
    My theory on this disaster, since everyone has one, is that either the
    debris impact or some other object struck the left leading edge reinforced
    carbon-carbon panels and damaged them. These U-shaped panels are attached
    side by side to the front spar of the wing.  Today Aviation Week reported
    that an Air Force telescope saw severe damage to the wing glove are of the
    leading edge.  If foreign object damage punctured the RCC substrate, a
    plasma jet could enter the leading edge pocket, where the Inconel brackets
    that hold the RCC panels are located.  Inconel X begins to lose its strength
    at around 1300 F, and the RCC panels reach around 2700 F, I think.  The
    original specs were for the leading edge to withstand a 1-inch puncture on
    the upper surface of any panel, but no punctures to the lower surfaces of
    panels 5-13 (middle section) due to the possiblity of plasma flow destroying
    the attachment hardware.   A program was instituted in 1998 to upgrade the
    insulation to withstand a quarter-inch puncture to the lower surface of
    panels 9-12, and 1-inch on panels 5-8 and thirteen.  This involved Nextel
    440 insulation (made by 3M) around the brackets to help deflect heat and
    plasma flow to protect them.  Columbia was to receive this in its
    just-finished OMDP.  I don't know if it received it or not.  But my theory
    (just conjecture) is that plasma penetrated the panel, destroyed some
    attachment hardware, and the panel came off.  This would account for the
    drag, and the plasma's journey into the wing would destroy the structure and
    maybe account for the fairly mild heating.  As for the sensor loss, I don't
    know enough about their location or wiring to say.
    Just venting my thoughts,
     Sam Milton
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