We never saw all of the layers, though, and the understanding was that it is a complex and fairly thick "cake".It’s not the normal coatings. We know from times when We have seen F22 in need of a reskin that those are not a metallic. Most of the airframe is coated in layers of composites from the surface down. Some of those materials are translucent to radar.
We have seen this mirror coating on experimental planes before, by scaled composite.Yes we never saw completely naked however, a lot of the materials used are shaped for the aerodynamics of the aircraft. Removing those materials and not filling would result in something that can’t fly. The Raptor’s ram isn’t skin deep it is the skin.
The nose cone has a radar under it as such it has to have materials that are transparent to the X band radar. As such those are left in the standard.
Whatever they are testing this isn’t a stripped bird it’s had her skin replaced.
That was the guess on those craft, as was testing new IRST technology as an alternative theory.We have seen this mirror coating on experimental planes before, by scaled composite.
Could it be to reflect directed energy?