What is this orange cover on shuttle SRB's for?

[David Hingtgen]

I've checked everywhere I know of but I can't find what they are. They seem to be removed prior to launch, but it always looks like there's nothing but a featureless white indentation underneath.

[Jay Chladek]

Its an access cover of sorts and indeed those yellow covers are removed prior to launch, leaving just the white cover underneath. I don't know with 100% certainty what the covers are there for, but I suspect it has something to do with the arming of the SRBs. The igniters for the solid fuel sit at the top of the SRBs, just below the forward skirts and those covers sit in that area. Prior to launch, some arming pins have to be pulled by the ground crew manually and I suspect the pins might be located behind those covers. So, the yellow covers would indicate SRBs that aren't armed while the white flight covers would indicate that you have live units.

BTW, the yellow covers protrude out from the SRBs a bit. They aren't flush mounted like what the decals in most model kits show. The white covers on the otherhand are recessed somewhat.