<A HREF="http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/tps/frcitiles.html" target="_new">http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/tps/frcitiles.html</A> <A HREF="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-tps.html#sts-frci" target="_new">http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-tps.html#sts-frci</A> <A HREF="http://www.manufacturing.net/esec/Article_150430.htm" target="_new">http://www.manufacturing.net/esec/Article_150430.htm</A> what if I threw a block of polyurethane foam shipping material onto the glass? nothing would happen! but i cannot get any materials data on compressive strenght of polyurethane versus the tiles. At least the tiles are fiber reinforced