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  1. #1
    Sam Wormley's Avatar
    Sam Wormley Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But itwas broke!



    Posted on Sun, Jul. 31, 2005
    Ref: http://www.contracostatimes.com/mld/...n/12269385.htm

    Old maxim didn't apply to NASA's foam problem
    By John Schwartz
    NEW YORK TIMES

    "We are ready to fly."

    It was June 24, and William Parsons, NASA's shuttle
    program manager, was speaking to reporters on a
    conference call from the Kennedy Space Center at
    Cape Canaveral, Fla.

    Two-and-a-half years of study and struggle, he told
    them, were over at long last.

    The shuttle Discovery could blast off in July.

    At a meeting that day, shuttle managers had ruled
    that the chances that debris from the external fuel
    tank would strike the Discovery at liftoff -- in
    the kind of accident that doomed the Columbia and
    its crew in 2003 -- had been reduced to "acceptable
    levels."

    The possibility that a large chunk of insulating
    foam might break away from a section of the tank
    called the protuberance air load ramp, or PAL,
    never came up.

    It had been ruled out months earlier, checked off
    on a long list of items no longer worthy of concern
    or of urgent action.

    Last Tuesday, NASA's view that it had produced the
    safest fuel tank in shuttle history was shattered
    two minutes into the flight of the Discovery. Two
    spacewalking astronauts tested repair techniques
    Saturday.

    The 0.9-pound piece of foam that fell from the PAL
    ramp on liftoff, which could have led to another
    catastrophe if it had ripped away a minute sooner,
    forced the immediate suspension of future shuttle
    flights until the problem could be resolved.

    How did it happen? An examination of the efforts to
    resolve the PAL ramp issues reveals a succession of
    missed opportunities and dubious judgments, not
    just in the two-and-a-half years since the Columbia
    disaster but over the life of the program.

    Potentially useful tests were not performed.
    Innovative solutions were not seriously pursued.
    Tantalizing clues were missed.

    In the end, the old engineering maxim "If it ain't
    broke, don't fix it" trumped misgivings about a
    part that had not shed any foam, as far as anyone
    knew, since 1983.

    "After two-and-a-half years, they should have been
    able to fix the foam," said Paul Czysz, a professor
    emeritus of aeronautical engineering at St. Louis
    University and a veteran consultant to NASA.

    Now, with the future of the International Space
    Station in the balance and the shuttle fleet just
    five years away from a mandatory retirement imposed
    by President Bush, NASA is still trying.

    In the dawn of the shuttle program, NASA rules said
    no foam at all should be allowed to hit the shuttle
    and possibly damage the fragile heat-resistant
    tiles that cover its aluminum skin.

    But fidelity to those standards was relaxed over
    time; in fact, foam fell off of the PAL ramp in two
    early missions, including the one in June 1983 on
    which Sally Ride became the first U.S. woman in
    space.

    There may have been many more incidents, but dozens
    of shuttle missions have been launched at night
    with no visual record of foam, and the tanks
    themselves are at the bottom of the ocean.

    As the early tank was replaced with two lighter
    successors, the PAL ramps remained -- one a 19-foot
    baffle along a channel for cables and pressurized
    lines along the forward end of the tank and the
    other a 37-foot strip along the flank of the
    cylindrical midsection of the fuel tank.

    And as experience showed NASA that shuttles
    returned safely despite more than 100 nicks and
    gouges requiring repair on many flights, the
    concerns abated over time.

    Until Feb. 1, 2003, the day the Columbia
    disintegrated on its way home to Cape Canaveral.

    After the accident, NASA examined all possible
    sources of liftoff debris, eventually identifying
    more than 170.

    The PAL ramp became a focus of attention: Like the
    bipod arm ramp, the part of the tank implicated in
    the Columbia disaster, it is covered with foam by
    hand.

    NASA conducted extensive wind-tunnel tests to
    determine whether the ramp could be removed.

    The tests of the ramp areas were all focused on
    aerodynamics -- helping determine how air would
    flow around the craft and tank, or to improve
    understanding of where foam or ice or other debris
    might fly should it fall free of the tank.

    But there were no tests of the PAL foam itself at
    speeds, pressures or vibrations experienced during
    ascent.

    So the only tests of how the material might hold up
    under the rigor of launching were the launchings
    themselves, with crew aboard.

    For many aeronautical engineers, a central rule in
    developing an aircraft is taking its components
    beyond the breaking point.

    Michael Griffin, NASA's new administrator and an
    engineer, said Friday, engineers believe, "If it
    ain't broke, don't fix it."

    "We debated and discussed whether the PAL ramp was
    broken" in the months that followed the Columbia
    disaster, Griffin continued.

    "The conclusion we came to was the wrong one, but
    the conclusion we came to after considerable study
    was that it was better to fly as is."

    NASA engineers had already seen how fixes can break
    things.

    After they made a minor change in the foam
    application process in the late 1990s to comply
    with environmental rules, small divots of foam
    rained off of the tank during ascent.

    The phenomenon, called popcorning, was caused by
    trapped bubbles; NASA solved the problem by venting
    the foam with tiny holes, but it was a reminder, if
    any was needed, that seemingly small changes can
    have profound effects.

    Ultimately, the accident board recommended that
    NASA find ways to prevent any shedding of foam or
    other debris. And NASA gained confidence during the
    time between flights that it was making progress.

    Among other things, it improved the training
    processes for applying foam by hand.

    At the Michoud tank assembly plant in Louisiana, an
    observer monitors every worker spraying foam --
    "for every sprayer there's a watcher, a second pair
    of eyes," said June Malone, a NASA spokeswoman.

    But the tank that flew with the Discovery last week
    was made before the new procedures went into
    effect, and NASA stopped short of requiring that
    the ramps be redone, said a spokesman, Martin
    Jensen.

    After the Columbia accident board issued its
    scathing report on the causes of the disintegration
    -- especially a "broken safety culture" at NASA
    that had grown complacent about all sorts of risks
    -- another independent group was set up to monitor
    NASA's progress in fulfilling the accident board's
    recommendations.

    That group, called the Stafford-Covey task force
    after the two former astronauts who led it,
    accepted NASA's argument that the PAL ramp did not
    urgently require alteration.

    At its final meeting in June, however, it also
    found that NASA had failed to meet the goal of
    eliminating all debris.

    The group took issue with the way NASA determined
    that the foam chunks that might still fall off the
    tank were too small to cause critical damage.

    And it criticized NASA's tendency to depend on
    computer simulations when physical experiments
    might yield more valuable data.

    Ultimately, however, the group accepted NASA's
    contention that it had raised the level of safety
    in general.

    A NASA engineer who works on tank safety issues
    said other areas of foam shedding from the
    Discovery's tank were even more troubling than the
    PAL ramp loss -- especially a divot that popped
    from the vicinity of the left-hand bipod strut, the
    spot that shed the foam that brought down Columbia.

    The loss of foam from that spot after so much work
    to correct the problem, he went on, proves that the
    problem is still far more complex than NASA
    understands.

    So the space agency is back to the drawing board.

    Copyright (c) 2005 New York Times

  2. #2
    jabara's Avatar
    jabara Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!


    "Sam Wormley" <swormley1@mchsi.com> wrote in message
    news:42ED855A.3070703@mchsi.com...


    Think about it.
    You have to spray a tank with foam that insulates and hardens at sea level.
    It is then exposed to severe vibration and less pressure, so the foam both
    expands and cracks.

    Bad design?
    Bad Foam, or could any Foam ever do the job?

    [Old Saying in rocket/aerospace industry, "FIFI" =>F*ck It, Fly It.]



  3. #3
    The Ghost In The Machine's Avatar
    The Ghost In The Machine Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!

    In sci.physics, jabara
    <spamnot@invalid.com>
    wrote
    on Sun, 31 Jul 2005 21:50:43 -0500
    <42ed8dfe$0$66073$892e7fe2@authen.white.readfreene ws.net>:

    I suspect no foam will ever work. Foam, after all, is
    substance + air. Air is under pressure (this is proven
    in a number of ways). The pressure goes down outside,
    the foam expands inside.

    If the bubble skin is thin enough, it might work --
    however, if not, well...

    (There is the remote possibility of placing the entire
    tank in a near-vacuum, or perhaps using steam to apply the
    foam, allowing the water vapor to fill the bubbles, which
    collapse when the steam cools sufficiently. The former
    looks highly impractical; the latter has the problem that
    the steam condenses to water, which may, given the wrong
    conditions, form a skin between foam and tank, ready
    to detach...)

    I'm beginning to wonder if they'll have to eschew the
    foam and fabricate a gigantic heating coil underneath the
    shuttle (between the bimounts). The main problem with
    that is that the heating element might break away too,
    in flight -- but it might beat being hit with chunks of ice,
    especially if the element is sprayed with some sort of
    epoxy or superglue.


    Then die in it, apparently. It's admittedly an interesting
    tradeoff: how much is an astronaut's life worth?

    (Considering that we get about 20 deaths in Iraq *per day*
    because of operations there, 17 deaths in the span of
    over 30 years isn't all that bad. But it's still 17 deaths.)

    --
    #191, ewill3@earthlink.net
    It's still legal to go .sigless.

  4. #4
    edward12@comcast.net's Avatar
    edward12@comcast.net Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!

    Hi Sam,

    I worried about "Go Fever"

    My Mother told me on Launch day she had a "Bad Feeling" about it.

    I guess we were right


  5. #5
    Guy Gordon's Avatar
    Guy Gordon Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!

    The Ghost In The Machine <ewill@sirius.athghost7038suus.net> wrote:


    And I suspect that fiber reinforcing will fix the problem.






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  6. #6
    jmfbahciv@aol.com's Avatar
    jmfbahciv@aol.com Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!

    In article <42b1s2-rp7.ln1@sirius.tg00suus7038.net>,
    The Ghost In The Machine <ewill@sirius.tg00suus7038.net> wrote:

    Prematurely? This shuttle is 25 years old, isn't it? I thought
    the lifetime of this technology was over a while ago.



    Debug the damned thing. I don't remember hearing about
    foam problems in the 80s. If these problems didn't exist
    back then, what changed to cause this foam to fall to
    pieces when shaked and baked.

    /BAH

    Subtract a hundred and four for e-mail.

  7. #7
    The Ghost In The Machine's Avatar
    The Ghost In The Machine Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!

    In sci.physics, Guy Gordon
    <gordon@NOSPAMwhite-crane.com>
    wrote
    on Mon, 01 Aug 2005 01:58:14 -0400
    <fdere1tertj8h8t9c3d1ajeq373tovm1ov@4ax.com>:

    It might, but then that wouldn't be pure foam, now, would it? :-)

    However, I also suspect the shuttle will simply be prematurely retired,
    unless they can get the foam up and running in the space of a month
    or two and retrofit the tank now slated for Atlantis.

    [.sigsnip]

    --
    #191, ewill3@earthlink.net
    It's still legal to go .sigless.

  8. #8
    The Ghost In The Machine's Avatar
    The Ghost In The Machine Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!

    In sci.physics, jmfbahciv@aol.com
    <jmfbahciv@aol.com>
    wrote
    on Mon, 01 Aug 05 09:12:31 GMT
    <FtednRrL7NwwmnPfRVn-oQ@rcn.net>:

    An interesting point; in an ideal world we'd have retired it in 1995.

    However, my understanding is that the revised plan suggests 2010 -- but
    that was before the latest grounding. It is entirely possible none
    of the other shuttles will ever fly again.


    Who says they didn't? Until 1986 the world probably didn't know
    O-rings existed, and they certainly hadn't considered that they
    could burn through.

    I suspect similar issues here.



    --
    #191, ewill3@earthlink.net
    It's still legal to go .sigless.

  9. #9
    Gregory L. Hansen's Avatar
    Gregory L. Hansen Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!

    In article <1122871281.408045.65280@z14g2000cwz.googlegroups. com>,
    edward12@comcast.net <edward12@comcast.net> wrote:


    My sister used a few expletives when she read about the launch in the
    morning newspaper. I didn't have strong feelings one way or the other.
    Looks like the ladies are 2 to 0.

    --
    "For every problem there is a solution which is simple, clean and wrong."
    -- Henry Louis Mencken

  10. #10
    Al Battlestown's Avatar
    Al Battlestown Guest

    Default Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!

    Using a reuseable vehicle that can enter space, leave space, and re-enter is
    the main problem. Too many extremes to have to deal with, many of which a
    computer will simply not be able to simulate properly.

    I felt it was a mistake to make something going into space that could be
    reuseable. Perhaps the return of the giant rocket like a Saturn V is needed
    with a small capsule for when a return is planned. Much less trouble with
    design because the capsule will only be used ONCE.

    In any case, as with anything else, there is a statistical probability that
    an accident will occur after every so many years. Just the laws of
    probability would dictate that. Add chaos theory and accidents are even
    more likely.

    Al


    "Sam Wormley" <swormley1@mchsi.com> wrote in message
    news:42ED855A.3070703@mchsi.com...



 

 
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