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Re: Old engineering maxim "If it ain't broke, don't fix it"... But it wa

Subject: Re: Old engineering maxim "If it ain't broke, don't fix it"... But it was broke!
From: The Ghost In The Machine
Date: Mon, 01 Aug 2005 04:00:04 GMT
Newsgroups: sci.astro.amateur, sci.physics
In sci.physics, jabara
<[email protected]>
on Sun, 31 Jul 2005 21:50:43 -0500
<[email protected]>:
> "Sam Wormley" <[email protected]> wrote in message
> news:[email protected]
>> Posted on Sun, Jul. 31, 2005
>> Ref:
>> Old maxim didn't apply to NASA's foam problem
>> By John Schwartz
>> "We are ready to fly."
> 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?

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.

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

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, [email protected]
It's still legal to go .sigless.

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