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I'm seeing this orange material within the windows of Columbia shuttles -- any thoughts on its precise function? The ISS's Cupola also contains similar international orange bands, though they seem less fabric-y there.


1 Answer 1


I can address "its precise function" although I don't know exactly what it was made of.

The pressurized crew compartment aka "crew module" of the shuttle Orbiter was a separate structure inside the outer hull, as seen in this diagram.

diagram showing crew compartment inside the hull

The Orbiter windows consisted of a rather complex system with the outer, thermal panes mounted on the outer hull, and the two inner, pressure panes mounted on the crew compartment.

The orange material you point out was a flexible joint aka "environmental barrier" connecting the thermal pane with the outer pressure aka "redundant" pane, as shown in this diagram.

cutaway drawing showing the three window panes

The flex joint was needed because there was a "window cavity conditioning system (WCCS)" that helped keep the windows clear. There were also prelaunch nitrogen purges of the cavity.

WCCS diagram

A closer-up sketch of the WCCS interface to the flex seal.

sketch of WCCS interface to environmental barrier

(I added the blue arrows and the red text)


Mechanical Systems Training Manual

1988 Press Reference Manual

Systems Training handout "Window Pane Failure Training"

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    $\begingroup$ Although I cannot "specifically" identify the orange material I can say that it looks very much like a type of fluorosilicone elastomer I've used in my design work. I know of various compositions, durometers, 'types' (open cell foam, closed cell foam, solid... all offered as sheet stock in various thicknesses). This particular orange material, if it is what I used, is a very high property FS solid sheet stock that is of moderately soft durometer that maintains flexibility over a very wide temp range. $\endgroup$
    – BradV
    Jul 14, 2022 at 22:33
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    $\begingroup$ I am most familiar with that color (in a general industrial context, not aerospace) being associated with silicone rubber, RTV or otherwise. $\endgroup$
    – ikrase
    Jul 16, 2022 at 7:48
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    $\begingroup$ @Organic_Marble Is "Window Pane Failure Training" available anywhere? $\endgroup$
    – ikrase
    Jul 16, 2022 at 7:48
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    $\begingroup$ @ikrase It is now. See updated answer. $\endgroup$ Jul 16, 2022 at 11:30

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