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Re: Apply shuttle ET foam in a vacuum.

Subject: Re: Apply shuttle ET foam in a vacuum.
From: George William Herbert
Date: Mon, 01 Aug 2005 08:33:05 -0000
Newsgroups: sci.astro.amateur, sci.space.policy, sci.space.shuttle
John Steinberg  <seesig@xxxxxxxxxx> wrote:
>Carsten A. Arnholm wrote:
>> Yes. Launch the shuttle first and *then* apply the foam. 
>
>FYI:
>http://facilities.grc.nasa.gov/spf/
>
>I've just done some very quick scratch figuring and the real answer
>isn't better foam application but rather a better ablative material.
>
>Turns out my materials science manual has the answer on page 831. 
>
>Duct tape.  

Alas, you neglect the OTHER reason there's foam on the 
external tank.

Lots of stuff is ablative to resist heat loads on ascent.
If that was all there was to it, there'd be a think spray on layer
of fiberglass or something there.

The pre-launch reason to have foam there is to prevent ice buildup
on the outside of the tank.  Because, if you think foam shedding is
bad for Shuttle Tiles and RCC leading edge sections, you should
see what ten pounds of nice solid liquid-hydrogen subchilled
water ice will do to any surface of the shuttle...

Foam on the outside does both jobs.  Foam on the inside of the tanks
would help prevent water ice buildup on the outside, but not help
with ascent heating.  External ablative shielding plus internal
foam would do both better than we get right now, but would be
heavier.

And any solution involving internal insulation will require
testing and safety validation.


-george william herbert
gherbert@xxxxxxxxx / gherbert@xxxxxxxxxxxxxxxxx




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