Can Polycarbonate be used for spacecraft windows?

I was under the impression that titanium was more common in spacecraft?

Nevertheless - in regards to polycarbonate - I'd think a principal issue is that PC resins have an upper working temperature of 130 decrees C. So even if PC was used as an inner pane, outer panes for thermal shielding would need to be made of another material.

As a side note, PC was used for the Apollo space helmets.

But in terms of structural windows, multi pane windows made from various "glass" type materials seems to be the preferred solution. On the space shuttle (quoted from a NASA document)

"The windows on the Space Shuttle are actually made out of aluminum silicate glass and fused silica glass. The orbiter windows are actually three different panes, there's an interior pressure pane because the pressure inside the orbiter is a lot higher than it is in the vacuum of space. We also have an optical pane that's installed in the middle that's about three and a half inches thick and on the outside, there's a thermal pane that protects the inside of the cockpit from the high heats of ascent and reentry."

You also may find this document from the Apollo era of interest:

http://www.lpi.usra.edu/lunar/documents/apolloSpac...

Spacecraft Windows

Polycarbonate would work, but plastic has a very high coefficient of thermal expansion compared to aluminum. The outer surfaces of spacecraft undergo large and rapid temperature swings. The mismatch between the thermal expansion of plastic and aluminum means that high stresses will be induced, eventually causing a failure.

It is much preferable to choose a material with a thermal expansion matched more closely to that of aluminum (of which most spacecraft are made).